Journal articles on the topic 'Chlamydomonas, flagella, ultrastructure analysis'
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1
Hou, Yuqing, Hongmin Qin, John A. Follit, Gregory J. Pazour, Joel L. Rosenbaum, and George B. Witman. "Functional analysis of an individual IFT protein: IFT46 is required for transport of outer dynein arms into flagella." Journal of Cell Biology 176, no. 5 (February 20, 2007): 653–65. http://dx.doi.org/10.1083/jcb.200608041.
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Intraflagellar transport (IFT), which is the bidirectional movement of particles within flagella, is required for flagellar assembly. IFT particles are composed of ∼16 proteins, which are organized into complexes A and B. We have cloned Chlamydomonas reinhardtii and mouse IFT46, and show that IFT46 is a highly conserved complex B protein in both organisms. A C. reinhardtii insertional mutant null for IFT46 has short, paralyzed flagella lacking dynein arms and with central pair defects. The mutant has greatly reduced levels of most complex B proteins, indicating that IFT46 is necessary for complex B stability. A partial suppressor mutation restores flagellar length to the ift46 mutant. IFT46 is still absent, but levels of the other IFT particle proteins are largely restored, indicating that complex B is stabilized in the suppressed strain. Axonemal ultrastructure is restored, except that the outer arms are still missing, although outer arm subunits are present in the cytoplasm. Thus, IFT46 is specifically required for transporting outer arms into the flagellum.
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Craige, Branch, Che-Chia Tsao, Dennis R. Diener, Yuqing Hou, Karl-Ferdinand Lechtreck, Joel L. Rosenbaum, and George B. Witman. "CEP290 tethers flagellar transition zone microtubules to the membrane and regulates flagellar protein content." Journal of Cell Biology 190, no. 5 (September 6, 2010): 927–40. http://dx.doi.org/10.1083/jcb.201006105.
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Mutations in human CEP290 cause cilia-related disorders that range in severity from isolated blindness to perinatal lethality. Here, we describe a Chlamydomonas reinhardtii mutant in which most of the CEP290 gene is deleted. Immunoelectron microscopy indicated that CEP290 is located in the flagellar transition zone in close association with the prominent microtubule–membrane links there. Ultrastructural analysis revealed defects in these microtubule–membrane connectors, resulting in loss of attachment of the flagellar membrane to the transition zone microtubules. Biochemical analysis of isolated flagella revealed that the mutant flagella have abnormal protein content, including abnormal levels of intraflagellar transport proteins and proteins associated with ciliopathies. Experiments with dikaryons showed that CEP290 at the transition zone is dynamic and undergoes rapid turnover. The results indicate that CEP290 is required to form microtubule–membrane linkers that tether the flagellar membrane to the transition zone microtubules, and is essential for controlling flagellar protein composition.
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Smith, E. F., and P. A. Lefebvre. "PF16 encodes a protein with armadillo repeats and localizes to a single microtubule of the central apparatus in Chlamydomonas flagella." Journal of Cell Biology 132, no. 3 (February 1, 1996): 359–70. http://dx.doi.org/10.1083/jcb.132.3.359.
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Several studies have indicated that the central pair of microtubules and their associated structures play a significant role in regulating flagellar motility. To begin a molecular analysis of these components we have generated central apparatus-defective mutants in Chlamydomonas reinhardtii using insertional mutagenesis. One paralyzed mutant recovered in our screen, D2, is an allele of a previously identified mutant, pf16. Mutant cells have paralyzed flagella, and the C1 microtubule of the central apparatus is missing in isolated axonemes. We have cloned the wild-type PF16 gene and confirmed its identity by rescuing pf16 mutants upon transformation. The rescued pf16 cells were wild-type in motility and in axonemal ultrastructure. A full-length cDNA clone for PF16 was obtained and sequenced. Database searches using the predicted 566 amino acid sequence of PF16 indicate that the protein contains eight contiguous armadillo repeats. A number of proteins with diverse cellular functions also contain armadillo repeats including pendulin, Rch1, importin, SRP-1, and armadillo. An antibody was raised against a fusion protein expressed from the cloned cDNA. Immunofluorescence labeling of wild-type flagella indicates that the PF16 protein is localized along the length of the flagella while immunogold labeling further localizes the PF16 protein to a single microtubule of the central pair. Based on the localization results and the presence of the armadillo repeats in this protein, we suggest that the PF16 gene product is involved in protein-protein interactions important for C1 central microtubule stability and flagellar motility.
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Smith, E. F., and P. A. Lefebvre. "PF20 gene product contains WD repeats and localizes to the intermicrotubule bridges in Chlamydomonas flagella." Molecular Biology of the Cell 8, no. 3 (March 1997): 455–67. http://dx.doi.org/10.1091/mbc.8.3.455.
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The central pair of microtubules and their associated structures play a significant role in regulating flagellar motility. To begin a molecular analysis of these components, we generated central apparatus-defective mutants in Chlamydomonas reinhardtii using insertional mutagenesis. One paralyzed mutant recovered in our screen contains an allele of a previously identified mutation, pf20. Mutant cells have paralyzed flagella, and the entire central apparatus is missing in isolated axonemes. We have cloned the wild-type PF20 gene and confirmed its identity by rescuing the pf20 mutant phenotype upon transformation. Rescued transformants were wild type in motility and in axonemal ultrastructure. A cDNA clone containing a single, long open reading frame was obtained and sequenced. Database searches using the predicted 606-amino acid sequence of PF20 indicate that the protein contains five contiguous WD repeats. These repeats are found in a number of proteins with diverse cellular functions including beta-transducin and dynein intermediate chains. An antibody was raised against a fusion protein expressed from the cloned cDNA. Immunogold labeling of wild-type axonemes indicates that the PF20 protein is localized along the length of the C2 microtubule on the intermicrotubule bridges connecting the two central microtubules. We suggest that the PF20 gene product is a new member of the family of WD repeat proteins and is required for central microtubule assembly and/or stability and flagellar motility.
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Pigino, Gaia, Stefan Geimer, Salvatore Lanzavecchia, Eugenio Paccagnini, Francesca Cantele, Dennis R. Diener, Joel L. Rosenbaum, and Pietro Lupetti. "Electron-tomographic analysis of intraflagellar transport particle trains in situ." Journal of Cell Biology 187, no. 1 (October 5, 2009): 135–48. http://dx.doi.org/10.1083/jcb.200905103.
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Intraflagellar transport (IFT) is the bidirectional movement of multipolypeptide particles between the ciliary membrane and the axonemal microtubules, and is required for the assembly, maintenance, and sensory function of cilia and flagella. In this paper, we present the first high-resolution ultrastructural analysis of trains of flagellar IFT particles, using transmission electron microscopy and electron-tomographic analysis of sections from flat-embedded Chlamydomonas reinhardtii cells. Using wild-type and mutant cells with defects in IFT, we identified two different types of IFT trains: long, narrow trains responsible for anterograde transport; and short, compact trains underlying retrograde IFT. Both types of trains have characteristic repeats and patterns that vary as one sections longitudinally through the trains of particles. The individual IFT particles are highly complex, bridged to each other and to the outer doublet microtubules, and are closely apposed to the inner surface of the flagellar membrane.
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Taillon, B. E., S. A. Adler, J. P. Suhan, and J. W. Jarvik. "Mutational analysis of centrin: an EF-hand protein associated with three distinct contractile fibers in the basal body apparatus of Chlamydomonas." Journal of Cell Biology 119, no. 6 (December 15, 1992): 1613–24. http://dx.doi.org/10.1083/jcb.119.6.1613.
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Centrin, a 20-kD phosphoprotein with four calcium-binding EF-hands, is present in the centrosome/basal body apparatus of the green alga Chlamydomonas reinhardtii in three distinct locations: the nucleus-basal body connectors, the distal striated fibers, and the flagellar transition regions. In each location, centrin is found in fibrous structures that display calcium-mediated contraction. The mutant vfl2 has structural defects at all of these locations and is defective for basal body localization and/or segregation. We show that the vfl2 mutation is a G-to-A transition in the centrin structural gene which converts a glutamic acid to a lysine at position 101, the first amino acid of the E-helix of the protein's third EF-hand. This proves that centrin is required to construct the nucleus-basal body connectors, the distal striated fibers, and the flagellar transition regions, and it demonstrates the importance of amino acid 101 to normal centrin function. Based on immunofluorescence analysis using anti-centrin antibodies, it appears that vfl2 centrin is capable of binding to the basal body but is incapable of polymerizing into filamentous structures. 19 phenotypic revertants of vfl2 were isolated, and 10 of them, each of which had undergone further mutation at codon 101, were examined in detail. At the DNA level, 1 of the 10 was wild type, and the other 9 were pseudorevertants encoding centrins with the amino acids asparagine, threonine, methionine, or isoleucine at position 101. No ultrastructure defects were apparent in the revertants with asparagine or threonine at position 101, but in those with methionine or isoleucine at position 101, the distal striated fibers were found to be incomplete, indicating that different amino acid substitutions at position 101 can differentially affect the assembly of the three distinct centrin-containing fibrous structures associated with the Chlamydomonas centrosome.
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Barsel, S. E., D. E. Wexler, and P. A. Lefebvre. "Genetic analysis of long-flagella mutants of Chlamydomonas reinhardtii." Genetics 118, no. 4 (April 1, 1988): 637–48. http://dx.doi.org/10.1093/genetics/118.4.637.
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Abstract The length of the flagella of Chlamydomonas reinhardtii cells is tightly regulated; both short-flagella and long-flagella mutants have been described. This report characterizes ten long-flagella mutants, including five newly isolated mutants, to determine the number of different loci conferring this phenotype, and to study interactions of mutants at different loci. The mutants, each of which was recessive in heterozygous diploids with wild type, fall into three unlinked complementation groups. One of these defines a new gene, lf3, which maps near the centromere of linkage group I. The flagellar length distributions in populations of each mutant were broad, with the longest flagella measuring four times the length of the longest flagella seen on wild-type cells. Each of the ten mutants had defective flagellar regrowth after amputation. Some of the mutants showed no regrowth within the time required for wild-type cells to regenerate flagella completely. Other mutants had subpopulations with rapid regeneration kinetics, and subpopulations with no observable regeneration. The mutants were each crossed to wild type to form temporary quadriflagellate, dikaryon cells; in each case the long flagella were rapidly shortened in the presence of the wild-type cytoplasm, demonstrating that the mutants were recessive, and that length control could be exerted on already assembled flagella.
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Boesger, Jens, Volker Wagner, Wolfram Weisheit, and Maria Mittag. "Analysis of Flagellar Phosphoproteins from Chlamydomonas reinhardtii." Eukaryotic Cell 8, no. 7 (May 8, 2009): 922–32. http://dx.doi.org/10.1128/ec.00067-09.
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ABSTRACT Cilia and flagella are cell organelles that are highly conserved throughout evolution. For many years, the green biflagellate alga Chlamydomonas reinhardtii has served as a model for examination of the structure and function of its flagella, which are similar to certain mammalian cilia. Proteome analysis revealed the presence of several kinases and protein phosphatases in these organelles. Reversible protein phosphorylation can control ciliary beating, motility, signaling, length, and assembly. Despite the importance of this posttranslational modification, the identities of many ciliary phosphoproteins and knowledge about their in vivo phosphorylation sites are still missing. Here we used immobilized metal affinity chromatography to enrich phosphopeptides from purified flagella and analyzed them by mass spectrometry. One hundred forty-one phosphorylated peptides were identified, belonging to 32 flagellar proteins. Thereby, 126 in vivo phosphorylation sites were determined. The flagellar phosphoproteome includes different structural and motor proteins, kinases, proteins with protein interaction domains, and many proteins whose functions are still unknown. In several cases, a dynamic phosphorylation pattern and clustering of phosphorylation sites were found, indicating a complex physiological status and specific control by reversible protein phosphorylation in the flagellum.
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Wingfield, Jenna, and Karl-Ferdinand Lechtreck. "Chlamydomonas Basal Bodies as Flagella Organizing Centers." Cells 7, no. 7 (July 17, 2018): 79. http://dx.doi.org/10.3390/cells7070079.
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During ciliogenesis, centrioles convert to membrane-docked basal bodies, which initiate the formation of cilia/flagella and template the nine doublet microtubules of the flagellar axoneme. The discovery that many human diseases and developmental disorders result from defects in flagella has fueled a strong interest in the analysis of flagellar assembly. Here, we will review the structure, function, and development of basal bodies in the unicellular green alga Chlamydomonas reinhardtii, a widely used model for the analysis of basal bodies and flagella. Intraflagellar transport (IFT), a flagella-specific protein shuttle critical for ciliogenesis, was first described in C. reinhardtii. A focus of this review will be on the role of the basal bodies in organizing the IFT machinery.
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VanWinkle-Swift, Karen, Kristin Baron, Alexander McNamara, Peter Minke, Cynthia Burrascano, and Janine Maddock. "The Chlamydomonas Zygospore: Mutant Strains of Chlamydomonas monoica Blocked in Zygospore Morphogenesis Comprise 46 Complementation Groups." Genetics 148, no. 1 (January 1, 1998): 131–37. http://dx.doi.org/10.1093/genetics/148.1.131.
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Abstract Chlamydomonas monoica undergoes homothallic sexual reproduction in response to nitrogen starvation. Mating pairs are established in clonal culture via flagellar agglutination and fuse by way of activated mating structures to form the quadriflagellate zygote. The zygote further matures into a dormant diploid zygospore through a series of events that we collectively refer to as zygosporulation. Mutants that arrest development prior to the completion of zygosporulation have been obtained through the use of a variety of mutagens, including ultraviolet irradiation, 5-fluorodeoxyuridine, ethyl methanesulfonate, and methyl methanesulfonate. Complementation analysis indicates that the present mutant collection includes alleles affecting 46 distinct zygote-specific functions. The frequency with which alleles at previously defined loci have been recovered in the most recent mutant searches suggests that as many as 30 additional zygote-specific loci may still remain to be identified. Nevertheless, the present collection should provide a powerful base for ultrastructural, biochemical, and molecular analysis of zygospore morphogenesis and dormancy in Chlamydomonas.
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Schneider, Mark J., Megan Ulland, and Roger D. Sloboda. "A Protein Methylation Pathway in Chlamydomonas Flagella Is Active during Flagellar Resorption." Molecular Biology of the Cell 19, no. 10 (October 2008): 4319–27. http://dx.doi.org/10.1091/mbc.e08-05-0470.
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During intraflagellar transport (IFT), the regulation of motor proteins, the loading and unloading of cargo and the turnover of flagellar proteins all occur at the flagellar tip. To begin an analysis of the protein composition of the flagellar tip, we used difference gel electrophoresis to compare long versus short (i.e., regenerating) flagella. The concentration of tip proteins should be higher relative to that of tubulin (which is constant per unit length of the flagellum) in short compared with long flagella. One protein we have identified is the cobalamin-independent form of methionine synthase (MetE). Antibodies to MetE label flagella in a punctate pattern reminiscent of IFT particle staining, and immunoblot analysis reveals that the amount of MetE in flagella is low in full-length flagella, increased in regenerating flagella, and highest in resorbing flagella. Four methylated proteins have been identified in resorbing flagella, using antibodies specific for asymmetrically dimethylated arginine residues. These proteins are found almost exclusively in the axonemal fraction, and the methylated forms of these proteins are essentially absent in full-length and regenerating flagella. Because most cells resorb cilia/flagella before cell division, these data indicate a link between flagellar protein methylation and progression through the cell cycle.
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Kannegaard, Elisa, E. Hesper Rego, Sebastian Schuck, Jessica L. Feldman, and Wallace F. Marshall. "Quantitative analysis and modeling of katanin function in flagellar length control." Molecular Biology of the Cell 25, no. 22 (November 5, 2014): 3686–98. http://dx.doi.org/10.1091/mbc.e14-06-1116.
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Flagellar length control in Chlamydomonas reinhardtii provides a simple model system in which to investigate the general question of how cells regulate organelle size. Previous work demonstrated that Chlamydomonas cytoplasm contains a pool of flagellar precursor proteins sufficient to assemble a half-length flagellum and that assembly of full-length flagella requires synthesis of additional precursors to augment the preexisting pool. The regulatory systems that control the synthesis and regeneration of this pool are not known, although transcriptional regulation clearly plays a role. We used quantitative analysis of length distributions to identify candidate genes controlling pool regeneration and found that a mutation in the p80 regulatory subunit of katanin, encoded by the PF15 gene in Chlamydomonas, alters flagellar length by changing the kinetics of precursor pool utilization. This finding suggests a model in which flagella compete with cytoplasmic microtubules for a fixed pool of tubulin, with katanin-mediated severing allowing easier access to this pool during flagellar assembly. We tested this model using a stochastic simulation that confirms that cytoplasmic microtubules can compete with flagella for a limited tubulin pool, showing that alteration of cytoplasmic microtubule severing could be sufficient to explain the effect of the pf15 mutations on flagellar length.
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Fox, L. A., K. E. Sawin, and W. S. Sale. "Kinesin-related proteins in eukaryotic flagella." Journal of Cell Science 107, no. 6 (June 1, 1994): 1545–50. http://dx.doi.org/10.1242/jcs.107.6.1545.
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To identify kinesin-related proteins that are important for ciliary and eukaryotic flagellar functions, we used affinity-purified, polyclonal antibodies to synthetic peptides corresponding to conserved sequences in the motor domain of kinesin (Sawin et al. (1992) J. Cell Sci. 101, 303–313). Using immunoblot analysis, two antibodies to distinct sequences (LNLVDLAGSE, ‘LAGSE’ and, HIPYRESKLT, ‘HIPYR’) reveal a family of proteins in flagella and axonemes isolated from Chlamydomonas. Similar analysis of axonemes from mutant Chlamydomonas strains or fractionated axonemes indicates that none of the immunoreactive proteins are associated with dynein arm or spoke structures. In contrast, one protein, approximately 110 kDa, is reduced in axonemes from mutant strains defective in the central pair apparatus. Immunoreactive proteins with masses of 96 and 97 kDa (the ‘97 kDa’ proteins) are selectively solubilized from isolated axonemes in 10 mM ATP. The 97 kDa proteins co-sediment in sucrose gradients at about 9 S and bind to axonemes or purified microtubules in a nucleotide-dependent fashion characteristic of kinesin. These results reveal that flagella contain kinesin-related proteins, which may be involved in axonemal central pair function and flagellar motility, or directed transport involved in morphogenesis or mating responses in Chlamydomonas.
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Geis, G., H. Leying, S. Suerbaum, U. Mai, and W. Opferkuch. "Ultrastructure and chemical analysis of Campylobacter pylori flagella." Journal of Clinical Microbiology 27, no. 3 (1989): 436–41. http://dx.doi.org/10.1128/jcm.27.3.436-441.1989.
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Kubo, Tomohiro, Masafumi Hirono, Takumi Aikawa, Ritsu Kamiya, and George B. Witman. "Reduced tubulin polyglutamylation suppresses flagellar shortness in Chlamydomonas." Molecular Biology of the Cell 26, no. 15 (August 2015): 2810–22. http://dx.doi.org/10.1091/mbc.e15-03-0182.
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Ciliary length control is an incompletely understood process essential for normal ciliary function. The flagella of Chlamydomonas mutants lacking multiple axonemal dyneins are shorter than normal; previously it was shown that this shortness can be suppressed by the mutation suppressor of shortness 1 ( ssh1) via an unknown mechanism. To elucidate this mechanism, we carried out genetic analysis of ssh1 and found that it is a new allele of TPG2 (hereafter tpg2-3), which encodes FAP234 functioning in tubulin polyglutamylation in the axoneme. Similar to the polyglutamylation-deficient mutants tpg1 and tpg2-1, tpg2-3 axonemal tubulin has a greatly reduced level of long polyglutamate side chains. We found that tpg1 and tpg2-1 mutations also promote flagellar elongation in short-flagella mutants, consistent with a polyglutamylation-dependent mechanism of suppression. Double mutants of tpg1 or tpg2-1 and fla10-1, a temperature-sensitive mutant of intraflagellar transport, underwent slower flagellar shortening than fla10-1 at restrictive temperatures, indicating that the rate of tubulin disassembly is decreased in the polyglutamylation-deficient flagella. Moreover, α-tubulin incorporation into the flagellar tips in temporary dikaryons was retarded in polyglutamylation-deficient flagella. These results show that polyglutamylation deficiency stabilizes axonemal microtubules, decelerating axonemal disassembly at the flagellar tip and shifting the axonemal assembly/disassembly balance toward assembly.
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Tam, Lai-Wa, William L. Dentler, and Paul A. Lefebvre. "Defective flagellar assembly and length regulation in LF3 null mutants in Chlamydomonas." Journal of Cell Biology 163, no. 3 (November 10, 2003): 597–607. http://dx.doi.org/10.1083/jcb.200307143.
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Four long-flagella (LF) genes are important for flagellar length control in Chlamydomonas reinhardtii. Here, we characterize two new null lf3 mutants whose phenotypes are different from previously identified lf3 mutants. These null mutants have unequal-length flagella that assemble more slowly than wild-type flagella, though their flagella can also reach abnormally long lengths. Prominent bulges are found at the distal ends of short, long, and regenerating flagella of these mutants. Analysis of the flagella by electron and immunofluorescence microscopy and by Western blots revealed that the bulges contain intraflagellar transport complexes, a defect reported previously (for review see Cole, D.G., 2003. Traffic. 4:435–442) in a subset of mutants defective in intraflagellar transport. We have cloned the wild-type LF3 gene and characterized a hypomorphic mutant allele of LF3. LF3p is a novel protein located predominantly in the cell body. It cosediments with the product of the LF1 gene in sucrose density gradients, indicating that these proteins may form a functional complex to regulate flagellar length and assembly.
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Goodenough, Ursula W. "Experimental analysis of the adhesion reaction between isolated Chlamydomonas flagella." Experimental Cell Research 166, no. 1 (September 1986): 237–46. http://dx.doi.org/10.1016/0014-4827(86)90523-9.
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Pazour, Gregory J., Nathan Agrin, John Leszyk, and George B. Witman. "Proteomic analysis of a eukaryotic cilium." Journal of Cell Biology 170, no. 1 (July 4, 2005): 103–13. http://dx.doi.org/10.1083/jcb.200504008.
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Cilia and flagella are widespread cell organelles that have been highly conserved throughout evolution and play important roles in motility, sensory perception, and the life cycles of eukaryotes ranging from protists to humans. Despite the ubiquity and importance of these organelles, their composition is not well known. Here we use mass spectrometry to identify proteins in purified flagella from the green alga Chlamydomonas reinhardtii. 360 proteins were identified with high confidence, and 292 more with moderate confidence. 97 out of 101 previously known flagellar proteins were found, indicating that this is a very complete dataset. The flagellar proteome is rich in motor and signal transduction components, and contains numerous proteins with homologues associated with diseases such as cystic kidney disease, male sterility, and hydrocephalus in humans and model vertebrates. The flagellum also contains many proteins that are conserved in humans but have not been previously characterized in any organism. The results indicate that flagella are far more complex than previously estimated.
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Asleson, Catherine M., and Paul A. Lefebvre. "Genetic Analysis of Flagellar Length Control in Chlamydomonas reinhardtii: A New Long-Flagella Locus and Extragenic Suppressor Mutations." Genetics 148, no. 2 (February 1, 1998): 693–702. http://dx.doi.org/10.1093/genetics/148.2.693.
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Abstract Flagellar length in the biflagellate alga Chlamydomonas reinhardtii is under constant and tight regulation. A number of mutants with defects in flagellar length control have been previously identified. Mutations in the three long-flagella (lf) loci result in flagella that are up to three times longer than wild-type length. In this article, we describe the isolation of long-flagellar mutants caused by mutations in a new LF locus, LF4. lf4 mutations were shown to be epistatic to lf1, while lf2 was found to be epistatic to lf4 with regard to the flagellar regeneration defect. Mutations in lf4 were able to suppress the synthetic flagella-less phenotype of the lf1, lf2 double mutant. In addition, we have isolated four extragenic suppressor mutations that suppress the long-flagella phenotype of lf1, lf2, or lf3 double mutants.
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Lenaghan, Scott C., Stefan Nwandu-Vincent, Benjamin E. Reese, and Mingjun Zhang. "Unlocking the secrets of multi-flagellated propulsion: drawing insights from Tritrichomonas foetus." Journal of The Royal Society Interface 11, no. 93 (April 6, 2014): 20131149. http://dx.doi.org/10.1098/rsif.2013.1149.
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In this work, a high-speed imaging platform and a resistive force theory (RFT) based model were applied to investigate multi-flagellated propulsion, using Tritrichomonas foetus as an example. We discovered that T. foetus has distinct flagellar beating motions for linear swimming and turning, similar to the ‘run and tumble’ strategies observed in bacteria and Chlamydomonas . Quantitative analysis of the motion of each flagellum was achieved by determining the average flagella beat motion for both linear swimming and turning, and using the velocity of the flagella as inputs into the RFT model. The experimental approach was used to calculate the curvature along the length of the flagella throughout each stroke. It was found that the curvatures of the anterior flagella do not decrease monotonically along their lengths, confirming the ciliary waveform of these flagella. Further, the stiffness of the flagella was experimentally measured using nanoindentation, allowing for calculation of the flexural rigidity of T. foetus' s flagella, 1.55×10 −21 N m 2 . Finally, using the RFT model, it was discovered that the propulsive force of T. foetus was similar to that of sperm and Chlamydomonas , indicating that multi-flagellated propulsion does not necessarily contribute to greater thrust generation, and may have evolved for greater manoeuvrability or sensing. The results from this study have demonstrated the highly coordinated nature of multi-flagellated propulsion and have provided significant insights into the biology of T. foetus .
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Huang, Kaiyao, Tim Kunkel, and Christoph F. Beck. "Localization of the Blue-Light Receptor Phototropin to the Flagella of the Green Alga Chlamydomonas reinhardtii." Molecular Biology of the Cell 15, no. 8 (August 2004): 3605–14. http://dx.doi.org/10.1091/mbc.e04-01-0010.
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Blue light controls the sexual life cycle of Chlamydomonas, mediated by phototropin, a UV-A/blue-light receptor that plays a prominent role in multiple photoresponses. By using fractionation experiments and immunolocalization studies, this blue-light receptor, in addition to its known localization to the cell bodies, also was detected in flagella. Within the flagella, it was completely associated with the axonemes, in striking contrast to the situation in higher plants and the Chlamydomonas cell body where phototropin was observed in the plasma membrane. Its localization was not perturbed in mutants lacking several prominent structural components of the axoneme. This led to the conclusion that phototropin may be associated with the outer doublet microtubules. Analysis of a mutant (fla10) in which intraflagellar transport is compromised suggested that phototropin is a cargo for intraflagellar transport. The blue-light receptor thus seems to be an integral constituent of the flagella of this green alga, extending the list of organisms that harbor sensory molecules within this organelle to unicellular algae.
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Johnson, K. A. "The axonemal microtubules of the Chlamydomonas flagellum differ in tubulin isoform content." Journal of Cell Science 111, no. 3 (February 1, 1998): 313–20. http://dx.doi.org/10.1242/jcs.111.3.313.
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Little is known of the molecular basis for the diversity of microtubule structure and function found within the eukaryotic flagellum. Antibodies that discriminate between tyrosinated alpha tubulin and post-translationally detyrosinated alpha tubulin were used to localize these complementary tubulin isoforms in flagella of the single-celled green alga Chlamydomonas reinhardtii. Immunofluorescence analysis of intact axonemes detected both isoforms along most of the lengths of flagella; however, each had a short distal zone rich in tyrosinated tubulin. Localizations on splayed axonemes revealed that the microtubules of the central-pair apparatus were rich in tyrosinated tubulin, while outer doublets contained a mixture of both isoforms. Immunoelectron analysis of individual outer doublets revealed that while tyrosinated tubulin was present in both A and B tubules, detyrosinated tubulin was largely confined to the wall of the B hemi-tubules. The absence of detyrosinated tubulin from the A tubules of the outer doublets and the microtubules of the central pair, both of which extend past the B hemi-tubules of the outer doublets in the flagellar tip, explained the appearance of a tyrosinated tubulin-rich distal zone on intact axonemes. Localizations performed on cells regenerating flagella revealed that flagellar assembly used tyrosinated tubulin; detyrosination of the B tubule occurred during later stages of regeneration, well after microtubule polymerization. The developmental timing of detyrosination, which occurs over a period during which the regrowing flagella begin to beat more effectively, suggests that post-translational modification of the B tubule surface may enhance dynein/B tubule interactions that power flagellar beating.
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Zhang, Y., Y. Luo, K. Emmett, and W. J. Snell. "Cell adhesion-dependent inactivation of a soluble protein kinase during fertilization in Chlamydomonas." Molecular Biology of the Cell 7, no. 4 (April 1996): 515–27. http://dx.doi.org/10.1091/mbc.7.4.515.
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Within seconds after the flagella of mt+ and mt- Chlamydomonas gametes adhere during fertilization, their flagellar adenylyl cyclase is activated several fold and preparation for cell fusion is initiated. Our previous studies indicated that early events in this pathway, including control of adenylyl cyclase, are regulated by phosphorylation and dephosphorylation. Here, we describe a soluble, flagellar protein kinase activity that is regulated by flagellar adhesion. A 48-kDa, soluble flagellar protein was consistently phosphorylated in an in vitro assay in flagella isolated from nonadhering mt+ and mt- gametes, but not in flagella isolated from mt+ and mt- gametes that had been adhering for 1 min. Although the 48-kDa protein was present in the flagella isolated from adhering gametes, we demonstrate that its protein kinase was inactivated by flagellar adhesion. Immunoblot analysis and inhibitor studies indicate that the 48-kDa protein in nonadhering gametes is phosphorylated by a protein tyrosine kinase. In vivo experiments showing that the protein tyrosine phosphatase inhibitor sodium orthovanadate inhibits fertilization suggest that protein dephosphorylation may be required for signal transduction. The 48-kDa protein and its protein kinase may be among the first elements of a novel signalling pathway that couples interaction of flagellar adhesion molecules to gamete activation.
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Heuser, T., CF Barber, J. Lin, J. Krell, M. Porter, and D. Nicastro. "Structural Analysis of the I1 Inner Dynein Arm Complex from Chlamydomonas Flagella." Microscopy and Microanalysis 16, S2 (July 2010): 1004–5. http://dx.doi.org/10.1017/s1431927610057594.
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Hamilton, Bradford S., Kazuo Nakamura, and Daniel A. K. Roncari. "Accumulation of starch in Chlamydomonas reinhardtii flagellar mutants." Biochemistry and Cell Biology 70, no. 3-4 (March 1, 1992): 255–58. http://dx.doi.org/10.1139/o92-039.
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Paralyzed flagellar mutants pf-1, pf-2, pf-7, and pf-18 of the green alga Chlamydomonas reinhardtii (Dangeard) were shown to store a significantly greater amount of starch than the motile wild type 137c+. The increase in starch storage was significant relative to protein, chlorophyll, and cell number. Analysis of average cell size revealed that the paralyzed mutants were larger than the wild type. This increase in storage molecule accumulation supports an inverse relationship between chemical energy storage and energy utilization for biomechanical/motile cellular functions. Chlamydomonas reinhardtii provides a useful model for studies of the role of cytoskeletal activity in the energy relationship and balance of organisms.Key words: Chlamydomonas, cytoskeleton, paralyzed flagella, starch, bioenergetics.
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Ahmed, Noveera T., and David R. Mitchell. "ODA16p, a Chlamydomonas Flagellar Protein Needed for Dynein Assembly." Molecular Biology of the Cell 16, no. 10 (October 2005): 5004–12. http://dx.doi.org/10.1091/mbc.e05-07-0627.
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Dynein motors of cilia and flagella function in the context of the axoneme, a very large network of microtubules and associated proteins. To understand how dyneins assemble and attach to this network, we characterized two Chlamydomonas outer arm dynein assembly (oda) mutants at a new locus, ODA16. Both oda16 mutants display a reduced beat frequency and altered swimming behavior, similar to previously characterized oda mutants, but only a partial loss of axonemal dyneins as shown by both electron microscopy and immunoblots. Motility studies suggest that the remaining outer arm dyneins on oda16 axonemes are functional. The ODA16 locus encodes a 49-kDa WD-repeat domain protein. Homologues were found in mammalian and fly databases, but not in yeast or nematode databases, implying that this protein is only needed in organisms with motile cilia or flagella. The Chlamydomonas ODA16 protein shares 62% identity with its human homologue. Western blot analysis localizes more than 90% of ODA16p to the flagellar matrix. Because wild-type axonemes retain little ODA16p but can be reactivated to a normal beat in vitro, we hypothesize that ODA16p is not an essential dynein subunit, but a protein necessary for dynein transport into the flagellar compartment or assembly onto the axoneme.
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Porter, M. E., S. Myster, C. Perrone, and E. O'Toole. "Molecular and Structural Studies on Dynein Associated Mutations in Chlamydomonas Flagella." Microscopy and Microanalysis 3, S2 (August 1997): 219–20. http://dx.doi.org/10.1017/s1431927600007984.
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The dynein ATPases are a large family of motor enzymes that provide the driving force for flagellar motility and contribute to microtubule-based transport inside cells. The challenge for the field is to appreciate the functional significance of the multiple dynein motors, to determine how the cell assembles a motor complex and targets each motor to its appropriate location, and to understand how a cell regulates the activity of each motor to accomplish its specific task(s). In our laboratory, we have capitalized on the highly ordered structural organization of the flagellar axoneme and on the ease of genetic analysis in Chlamydomonas to ask how a single cell controls the assembly and activity of its multiple flagellar dyneins. In particular, we have focused our efforts on the inner dynein arms, which are both necessary and sufficient for normal flagellar motility. The significance of this work derives from the conservation of axoneme structure across species, as well as the numerous functional homologies between the flagellar and cytoplasmic dyneins.
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Böddeker, Thomas J., Stefan Karpitschka, Christian T. Kreis, Quentin Magdelaine, and Oliver Bäumchen. "Dynamic force measurements on swimming Chlamydomonas cells using micropipette force sensors." Journal of The Royal Society Interface 17, no. 162 (January 2020): 20190580. http://dx.doi.org/10.1098/rsif.2019.0580.
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Flagella and cilia are cellular appendages that inherit essential functions of microbial life including sensing and navigating the environment. In order to propel a swimming microorganism they displace the surrounding fluid by means of periodic motions, while precisely timed modulations of their beating patterns enable the cell to steer towards or away from specific locations. Characterizing the dynamic forces, however, is challenging and typically relies on indirect experimental approaches. Here, we present direct in vivo measurements of the dynamic forces of motile Chlamydomonas reinhardtii cells in controlled environments. The experiments are based on partially aspirating a living microorganism at the tip of a micropipette force sensor and optically recording the micropipette’s position fluctuations with high temporal and sub-pixel spatial resolution. Spectral signal analysis allows for isolating the cell-generated dynamic forces caused by the periodic motion of the flagella from background noise. We provide an analytic, elasto-hydrodynamic model for the micropipette force sensor and describe how to obtain the micropipette’s full frequency response function from a dynamic force calibration. Using this approach, we measure the amplitude of the oscillatory forces during the swimming activity of individual Chlamydomonas reinhardtii cells of 26 ± 5 pN, resulting from the coordinated flagellar beating with a frequency of 49 ± 5 Hz. This dynamic micropipette force sensor technique generalizes the applicability of micropipettes as force sensors from static to dynamic force measurements, yielding a force sensitivity in the piconewton range. In addition to measurements in bulk liquid environment, we study the dynamic forces of the biflagellated microswimmer in the vicinity of a solid/liquid interface. As we gradually decrease the distance of the swimming microbe to the interface, we measure a significantly enhanced force transduction at distances larger than the maximum extent of the beating flagella, highlighting the importance of hydrodynamic interactions for scenarios in which flagellated microorganisms encounter surfaces.
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Engel, Benjamin D., Hiroaki Ishikawa, Kimberly A. Wemmer, Stefan Geimer, Ken-ichi Wakabayashi, Masafumi Hirono, Branch Craige, et al. "The role of retrograde intraflagellar transport in flagellar assembly, maintenance, and function." Journal of Cell Biology 199, no. 1 (October 1, 2012): 151–67. http://dx.doi.org/10.1083/jcb.201206068.
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The maintenance of flagellar length is believed to require both anterograde and retrograde intraflagellar transport (IFT). However, it is difficult to uncouple the functions of retrograde transport from anterograde, as null mutants in dynein heavy chain 1b (DHC1b) have stumpy flagella, demonstrating solely that retrograde IFT is required for flagellar assembly. We isolated a Chlamydomonas reinhardtii mutant (dhc1b-3) with a temperature-sensitive defect in DHC1b, enabling inducible inhibition of retrograde IFT in full-length flagella. Although dhc1b-3 flagella at the nonpermissive temperature (34°C) showed a dramatic reduction of retrograde IFT, they remained nearly full-length for many hours. However, dhc1b-3 cells at 34°C had strong defects in flagellar assembly after cell division or pH shock. Furthermore, dhc1b-3 cells displayed altered phototaxis and flagellar beat. Thus, robust retrograde IFT is required for flagellar assembly and function but is dispensable for the maintenance of flagellar length. Proteomic analysis of dhc1b-3 flagella revealed distinct classes of proteins that change in abundance when retrograde IFT is inhibited.
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Pigino, Gaia, Aditi Maheshwari, Khanh Huy Bui, Chikako Shingyoji, Shinji Kamimura, and Takashi Ishikawa. "Comparative structural analysis of eukaryotic flagella and cilia from Chlamydomonas, Tetrahymena, and sea urchins." Journal of Structural Biology 178, no. 2 (May 2012): 199–206. http://dx.doi.org/10.1016/j.jsb.2012.02.012.
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Hoops, H. J., and G. B. Witman. "Basal bodies and associated structures are not required for normal flagellar motion or phototaxis in the green alga Chlorogonium elongatum." Journal of Cell Biology 100, no. 1 (January 1, 1985): 297–309. http://dx.doi.org/10.1083/jcb.100.1.297.
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The interphase flagellar apparatus of the green alga Chlorogonium elongatum resembles that of Chlamydomonas reinhardtii in the possession of microtubular rootlets and striated fibers. However, Chlorogonium, unlike Chlamydomonas, retains functional flagella during cell division. In dividing cells, the basal bodies and associated structures are no longer present at the flagellar bases, but have apparently detached and migrated towards the cell equator before the first mitosis. The transition regions remain with the flagella, which are now attached to a large apical mitochondrion by cross-striated filamentous components. Both dividing and nondividing cells of Chlorogonium propagate asymmetrical ciliary-type waveforms during forward swimming and symmetrical flagellar-type waveforms during reverse swimming. High-speed cinephotomicrographic analysis indicates that waveforms, beat frequency, and flagellar coordination are similar in both cell types. This indicates that basal bodies, striated fibers, and microtubular rootlets are not required for the initiation of flagellar beat, coordination of the two flagella, or determination of flagellar waveform. Dividing cells display a strong net negative phototaxis comparable to that of nondividing cells; hence, none of these structures are required for the transmission or processing of the signals involved in phototaxis, or for the changes in flagellar beat that lead to phototactic turning. Therefore, all of the machinery directly involved in the control of flagellar motion is contained within the axoneme and/or transition region. The timing of formation and the positioning of the newly formed basal structures in each of the daughter cells suggests that they play a significant role in cellular morphogenesis.
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Ramaswamy, Shivaraman, Dhananjay Suresh, Harsha Bathula, Ojas Mahapatra, Kantha D. Arunachalam, and C. Gopalakrishnan. "Nanoscale Analysis of Surface Topography and Adhesion Force Measurements of Flagella Isolated from Chlamydomonas reinhardtii." Journal of Advanced Microscopy Research 8, no. 3 (September 1, 2013): 163–70. http://dx.doi.org/10.1166/jamr.2013.1154.
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Hoops, H. J. "Flagellar, cellular and organismal polarity in Volvox carteri." Journal of Cell Science 104, no. 1 (January 1, 1993): 105–17. http://dx.doi.org/10.1242/jcs.104.1.105.
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It has previously been shown that the flagellar apparatus of the mature Volvox carteri somatic cell lacks the 180° rotational symmetry typical of most unicellular green algae. This asymmetry has been postulated to be the result of rotation of each half of the flagellar apparatus. Here it is shown that V. carteri axonemes contain polarity markers that are similar to those found in Chlamydomonas, except that in V. carteri the number one doublets do not face each other as they do in Chlamydomonas but are oriented in parallel and at approximately right angles to the line that connects the flagella. Thus, the rotational orientations of the axonemes are consistent with the postulate that the flagella of V. carteri have rotated in opposite directions, as was predicted earlier from the positions of the basal fibers and microtubular rootlets. Moreover, high-speed cinephotomicrographic analysis shows that the V. carteri flagellar effective strokes are also oriented in approximately the same direction, and in parallel planes. These results suggest that the direction of the effective stroke in both Chlamydomonas and Volvox is fixed, and that rotation of the axoneme is the cause of the differences in flagellar motility observed between Chlamydomonas and Volvox. These differences are probably essential for effective organismal motility. Cellular polarity of V. carteri can be related to that of Chlamydomonas after taking into account the developmental reorientation of flagellar apparatus components. This reorientation also results in the movement of the eyespot from a position nearer one of the flagellar bases to a position approximately equidistant between them. By analogy to Chlamydomonas, the anti side of the V. carteri somatic cell faces the spheroid anterior, the syn side faces the spheroid posterior. The cis side of the cell is to the cell's left (the right to an outside observer), although it cannot be described solely on the basis of eyespot position as it can in Chlamydomonas, while the trans side is to the cell's right. It follows that if the direction of the effective flagellar stroke is specified by structural features, then effective organismal motility in V. carteri, will be accomplished only if the cells are held in the proper orientation with respect to one another. The simplest arrangement that will yield both progression and rotation in ovoid or spherical colonies composed of biflagellate isokont cells is one in which the cells are arranged with rotational symmetry about the anterior-posterior axis of the spheroid. Analysis of the polarity of somatic cells from throughout the spheroid shows that it is constructed with just such symmetry. This symmetry probably originates with the very first divisions.
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Dymek, Erin E., Thomas Heuser, Daniela Nicastro, and Elizabeth F. Smith. "The CSC is required for complete radial spoke assembly and wild-type ciliary motility." Molecular Biology of the Cell 22, no. 14 (July 15, 2011): 2520–31. http://dx.doi.org/10.1091/mbc.e11-03-0271.
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The ubiquitous calcium binding protein, calmodulin (CaM), plays a major role in regulating the motility of all eukaryotic cilia and flagella. We previously identified a CaM and Spoke associated Complex (CSC) and provided evidence that this complex mediates regulatory signals between the radial spokes and dynein arms. We have now used an artificial microRNA (amiRNA) approach to reduce expression of two CSC subunits in Chlamydomonas. For all amiRNA mutants, the entire CSC is lacking or severely reduced in flagella. Structural studies of mutant axonemes revealed that assembly of radial spoke 2 is defective. Furthermore, analysis of both flagellar beating and microtubule sliding in vitro demonstrates that the CSC plays a critical role in modulating dynein activity. Our results not only indicate that the CSC is required for spoke assembly and wild-type motility, but also provide evidence for heterogeneity among the radial spokes.
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Tam, Lai-Wa, Nedra F. Wilson, and Paul A. Lefebvre. "A CDK-related kinase regulates the length and assembly of flagella in Chlamydomonas." Journal of Cell Biology 176, no. 6 (March 12, 2007): 819–29. http://dx.doi.org/10.1083/jcb.200610022.
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Little is known about how cells regulate the size of their organelles. In this study, we find that proper flagellar length control in Chlamydomonas reinhardtii requires the activity of a new member of the cyclin-dependent kinase (CDK) family, which is encoded by the LF2 (long flagella 2) gene. This novel CDK contains all of the important residues that are essential for kinase activity but lacks the cyclin-binding motif PSTAIRE. Analysis of genetic lesions in a series of lf2 mutant alleles and site-directed mutagenesis of LF2p reveals that improper flagellar length and defective flagellar assembly correlate with the extent of disruption of conserved kinase structures or residues by mutations. LF2p appears to interact with both LF1p and LF3p in the cytoplasm, as indicated by immunofluorescence localization, sucrose density gradients, cell fractionation, and yeast two-hybrid experiments. We propose that LF2p is the catalytic subunit of a regulatory kinase complex that controls flagellar length and flagellar assembly.
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Cheshire, J. L., and L. R. Keller. "Uncoupling of Chlamydomonas flagellar gene expression and outgrowth from flagellar excision by manipulation of Ca2+." Journal of Cell Biology 115, no. 6 (December 15, 1991): 1651–59. http://dx.doi.org/10.1083/jcb.115.6.1651.
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Chlamydomonas cells respond to certain environmental stimuli by shedding their flagella. Flagellar loss induces a rapid, transient increase in expression of a specific set of genes encoding flagellar proteins, and assembly of a new flagellar pair. While flagellar gene expression and initiation of flagellar outgrowth are normally tightly coupled to flagellar excision, our results demonstrate that these processes can be uncoupled by manipulating Ca2+ levels or calmodulin activity. In our experiments, wild-type cells were stimulated to excise their flagella using mechanical shearing, and at times after deflagellation, flagellar lengths were measured and flagellar mRNA abundance changes were determined by S1 nuclease protection analysis. When extracellular Ca2+ was lowered by addition of EGTA to cultures before excision, flagellar mRNA abundance changes and flagellar outgrowth were temporally uncoupled from flagellar excision. When extracellular Ca2+ was lowered immediately after excision or when calmodulin activity was inhibited with W-7, flagellar outgrowth was uncoupled from flagellar excision and flagellar mRNA abundance changes. Whenever events in the process of flagellar regeneration were temporally uncoupled, the magnitude of the flagellar mRNA abundance change was reduced. These results suggest that flagellar gene expression may be regulated by multiple signals generated from these events, and implicate Ca2+ as a factor in the mechanisms controlling flagellar regeneration.
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Dai, Jin, Francesco Barbieri, David R. Mitchell, and Karl F. Lechtreck. "In vivo analysis of outer arm dynein transport reveals cargo-specific intraflagellar transport properties." Molecular Biology of the Cell 29, no. 21 (October 15, 2018): 2553–65. http://dx.doi.org/10.1091/mbc.e18-05-0291.
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Outer dynein arms (ODAs) are multiprotein complexes that drive flagellar beating. Based on genetic and biochemical analyses, ODAs preassemble in the cell body and then move into the flagellum by intraflagellar transport (IFT). To study ODA transport in vivo, we expressed the essential intermediate chain 2 tagged with mNeonGreen (IC2-NG) to rescue the corresponding Chlamydomonas reinhardtii mutant oda6. IC2-NG moved by IFT; the transport was of low processivity and increased in frequency during flagellar growth. As expected, IFT of IC2-NG was diminished in oda16, lacking an ODA-specific IFT adapter, and in ift46 IFT46ΔN lacking the ODA16-interacting portion of IFT46. IFT loading appears to involve ODA16-dependent recruitment of ODAs to basal bodies followed by handover to IFT. Upon unloading from IFT, ODAs rapidly docked to the axoneme. Transient docking still occurred in the docking complex mutant oda3 indicating that the docking complex stabilizes rather than initiates ODA–microtubule interactions. In full-length flagella, ODAs continued to enter and move inside cilia by short-term bidirectional IFT and diffusion and the newly imported complexes frequently replaced axoneme-bound ODAs. We propose that the low processivity of ODA-IFT contributes to flagellar maintenance by ensuring the availability of replacement ODAs along the length of flagella.
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Mitchell, D. R., and J. L. Rosenbaum. "A motile Chlamydomonas flagellar mutant that lacks outer dynein arms." Journal of Cell Biology 100, no. 4 (April 1, 1985): 1228–34. http://dx.doi.org/10.1083/jcb.100.4.1228.
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A new Chlamydomonas flagellar mutant, pf-28, which swims more slowly than wild-type cells, was selected. Thin-section electron microscopy revealed the complete absence of outer-row dynein arms in this mutant, whereas inner-row arms and other axonemal structures appeared normal. SDS PAGE analysis also indicated that polypeptides previously identified as outer-arm dynein components are completely absent in pf-28. The two ATPases retained by this mutant sediment at 17.7S and 12.7S on sucrose gradients that contain 0.6 M KCl. Overall swimming patterns of pf-28 differ little from wild-type except that forward swimming speed is reduced to 35% of the wild-type value, and cells show little or no backward movement during photophobic avoidance. Mutant cells will respond to phototactic stimuli, and their flagella will beat in either the forward or reverse mode. This is the first report of a mutant that lacks dynein arms that can swim.
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Dutcher, S. K., W. Gibbons, and W. B. Inwood. "A genetic analysis of suppressors of the PF10 mutation in Chlamydomonas reinhardtii." Genetics 120, no. 4 (December 1, 1988): 965–76. http://dx.doi.org/10.1093/genetics/120.4.965.
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Abstract A mutation at the PF10 locus of the unicellular green alga Chlamydomonas reinhardtii leads to abnormal cell motility. The asymmetric form of the ciliary beat stroke characteristic of wild-type flagella is modified by this mutation to a nearly symmetric beat. We report here that this abnormal motility is a conditional phenotype that depends on light intensity. In the absence of light or under low light intensities, the motility is more severely impaired than at higher light intensities. By UV mutagenesis we obtained 11 intragenic and 70 extragenic strains that show reversion of the pf10 motility phenotype observed in low light. The intragenic events reverted the motility phenotype of the pf10 mutation completely. The extragenic events define at least seven suppressor loci; these map to linkage groups IV, VII, IX, XI, XII and XVII. Suppressor mutations at two of the seven loci (LIS1 and LIS2) require light for their suppressor activity. Forty-eight of the 70 extragenic suppressors were examined in heterozygous diploid cells; 47 of these mutants were recessive to the wild-type allele and one mutant (bop5-1) was dominant to the wild-type allele. Complementation analysis of the 47 recessive mutants showed unusual patterns. Most mutants within a recombinationally defined group failed to complement one another, although there were pairs that showed intra-allelic complementation. Additionally, some of the mutants at each recombinationally defined locus failed to complement mutants at other loci. They define dominant enhancers of one another.
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Periz, Goran, Darshita Dharia, Steven H. Miller, and Laura R. Keller. "Flagellar Elongation and Gene Expression in Chlamydomonas reinhardtii." Eukaryotic Cell 6, no. 8 (June 15, 2007): 1411–20. http://dx.doi.org/10.1128/ec.00167-07.
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ABSTRACT Lithium (Li+) affects the physiology of cells from a broad range of organisms including plants and both vertebrate and invertebrate animals. Although its effects result presumably from changes in gene expression elicited by its interaction with intracellular signal transduction pathways, the molecular mechanisms of Li+ action are not well understood. The biflagellate green alga Chlamydomonas reinhardtii is an ideal genetic model for the integration of the effects on Li+ on signal transduction, gene expression, and aspects of flagellar biogenesis. Li+ causes C. reinhardtii flagella to elongate to ∼1.4 times their normal length and blocks flagellar motility (S. Nakamura, H. Tabino, and M. K. Kojima, Cell Struct. Funct. 12:369-374, 1987). We report here that Li+ treatment increases the abundance of several flagellar mRNAs, including α- and β-tubulin and pcf3-21. Li+-induced flagellar gene expression occurs in cells pretreated with cycloheximide, suggesting that the abundance change is a response that does not require new protein synthesis. Deletion analysis of the flagellar α1-tubulin gene promoter showed that sequences necessary for Li+-induced expression differed from those for acid shock induction and contain a consensus binding site for CREB/ATF and AP-1 transcription factors. These studies suggest potential promoter elements, candidate factors, and signal transduction pathways that may coordinate the C. reinhardtii cellular response to Li+.
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Gokhale, Avanti, Maureen Wirschell, and Winfield S. Sale. "Regulation of dynein-driven microtubule sliding by the axonemal protein kinase CK1 in Chlamydomonas flagella." Journal of Cell Biology 186, no. 6 (September 14, 2009): 817–24. http://dx.doi.org/10.1083/jcb.200906168.
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Experimental analysis of isolated ciliary/flagellar axonemes has implicated the protein kinase casein kinase I (CK1) in regulation of dynein. To test this hypothesis, we developed a novel in vitro reconstitution approach using purified recombinant Chlamydomonas reinhardtii CK1, together with CK1-depleted axonemes from the paralyzed flagellar mutant pf17, which is defective in radial spokes and impaired in dynein-driven microtubule sliding. The CK1 inhibitors (DRB and CK1-7) and solubilization of CK1 restored microtubule sliding in pf17 axonemes, which is consistent with an inhibitory role for CK1. The phosphatase inhibitor microcystin-LR blocked rescue of microtubule sliding, indicating that the axonemal phosphatases, required for rescue, were retained in the CK1-depleted axonemes. Reconstitution of depleted axonemes with purified, recombinant CK1 restored inhibition of microtubule sliding in a DRB– and CK1-7–sensitive manner. In contrast, a purified “kinase-dead” CK1 failed to restore inhibition. These results firmly establish that an axonemal CK1 regulates dynein activity and flagellar motility.
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Tam, L. W., and P. A. Lefebvre. "Cloning of flagellar genes in Chlamydomonas reinhardtii by DNA insertional mutagenesis." Genetics 135, no. 2 (October 1, 1993): 375–84. http://dx.doi.org/10.1093/genetics/135.2.375.
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Abstract Chlamydomonas is a popular genetic model system for studying many cellular processes. In this report, we describe a new approach to isolate Chlamydomonas genes using the cloned nitrate reductase gene (NIT1) as an insertional mutagen. A linearized plasmid containing the NIT1 gene was introduced into nit1 mutant cells by glass-bead transformation. Of 3000 Nit+ transformants examined, 74 showed motility defects of a wide range of phenotypes, suggesting that DNA transformation is an effective method for mutagenizing cells. For 13 of 15 such motility mutants backcrossed to nit- mutant strains, the motility phenotype cosegregated with the Nit+ phenotype, indicating that the motility defects of these 13 mutants may be caused by integration of the plasmid. Further genetic analysis indicated that three of these mutants contained alleles of previously identified loci: mbo2 (move backward only), pf13 (paralyzed flagella) and vfl1 (variable flagellar number). Three other abnormal-flagellar-number mutants did not map to any previously described loci at which mutations produce similar phenotypes. Genomic sequences flanking the integrated plasmid in the mbo2 and vfl1 mutants were isolated and used as probes to obtain wild-type genomic clones, which complemented the motility defects upon transformation into cells. Our results demonstrate the potential of this new approach for cloning genes identified by mutation in Chlamydomonas.
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O'Toole, Eileen T., Thomas H. Giddings, Mary E. Porter, and Lawrence E. Ostrowski. "Computer-assisted image analysis of human cilia and Chlamydomonas flagella reveals both similarities and differences in axoneme structure." Cytoskeleton 69, no. 8 (May 22, 2012): 577–90. http://dx.doi.org/10.1002/cm.21035.
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Piperno, G., Z. Ramanis, E. F. Smith, and W. S. Sale. "Three distinct inner dynein arms in Chlamydomonas flagella: molecular composition and location in the axoneme." Journal of Cell Biology 110, no. 2 (February 1, 1990): 379–89. http://dx.doi.org/10.1083/jcb.110.2.379.
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The molecular composition and organization of the row of axonemal inner dynein arms were investigated by biochemical and electron microscopic analyses of Chlamydomonas wild-type and mutant axonemes. Three inner arm structures could be distinguished on the basis of their molecular composition and position in the axoneme as determined by analysis of pf30 and pf23 mutants. The three inner arm structures repeat every 96 nm and are referred to here as inner arms I1, I2, and I3. I1 is proximal to the radial spoke S1, whereas I2 and I3 are distal to spokes S1 and S2, respectively. The mutant pf30 lacks I1 whereas the mutant pf23 lacks both I1 and I2 but has a normal inner arm I3. Each of the six heavy chains that was identified as an inner dynein arm subunit has a site for ATP binding and hydrolysis. Two of the heavy chains together with a polypeptide of 140,000 molecular weight form the inner arm I1 and were extracted from the axoneme as a complex that had a sedimentation coefficient close to 21S at high ionic strength. Different subsets of two of the remaining four heavy chains form the inner arms I2 and I3. These arms at high ionic strength are dissociated as 11S particles that include one heavy chain, one intermediate chain, two light chains, and actin. These and other lines of evidence indicate that the inner arm I1 is different in structure and function from the inner arms I2 and I3.
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Wagner, Volker, Gunther Geßner, Ines Heiland, Marc Kaminski, Susan Hawat, Kai Scheffler, and Maria Mittag. "Analysis of the Phosphoproteome of Chlamydomonas reinhardtii Provides New Insights into Various Cellular Pathways." Eukaryotic Cell 5, no. 3 (March 2006): 457–68. http://dx.doi.org/10.1128/ec.5.3.457-468.2006.
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ABSTRACT The unicellular flagellated green alga Chlamydomonas reinhardtii has emerged as a model organism for the study of a variety of cellular processes. Posttranslational control via protein phosphorylation plays a key role in signal transduction, regulation of gene expression, and control of metabolism. Thus, analysis of the phosphoproteome of C. reinhardtii can significantly enhance our understanding of various regulatory pathways. In this study, we have grown C. reinhardtii cultures in the presence of an inhibitor of Ser/Thr phosphatases to increase the phosphoprotein pool. Phosphopeptides from these cells were enriched by immobilized metal-ion affinity chromatography and analyzed by nano-liquid chromatography-electrospray ionization-mass spectrometry (MS) with MS-MS as well as neutral-loss-triggered MS-MS-MS spectra. In this way, we were able to identify 360 phosphopeptides from 328 different phosphoproteins of C. reinhardtii, thus providing new insights into a variety of cellular processes, including metabolic and signaling pathways. Comparative analysis of the phosphoproteome also yielded new functional information on proteins controlled by redox regulation (thioredoxin target proteins) and proteins of the chloroplast 70S ribosome, the centriole, and especially the flagella, for which 32 phosphoproteins were identified. The high yield of phosphoproteins of the latter correlates well with the presence of several flagellar kinases and indicates that phosphorylation/dephosphorylation represents one of the key regulatory mechanisms of eukaryotic cilia. Our data also provide new insights into certain cilium-related mammalian diseases.
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Zhu, Xiaoyan, Emiliya Poghosyan, Lenka Rezabkova, Bridget Mehall, Hitoshi Sakakibara, Masafumi Hirono, Ritsu Kamiya, Takashi Ishikawa, and Pinfen Yang. "The roles of a flagellar HSP40 ensuring rhythmic beating." Molecular Biology of the Cell 30, no. 2 (January 15, 2019): 228–41. http://dx.doi.org/10.1091/mbc.e18-01-0047.
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HSP40s are regarded as cochaperones, perpetually shuttling client polypeptides to HSP70s for refolding. However, many HSP40s that are central for disparate processes diverge from this paradigm. To elucidate the noncanonical mechanisms, we investigated HSP40 in the radial spoke (RS) complex in flagella. Disruption of the gene by the MRC1 transposon in Chlamydomonas resulted in jerky flagella. Traditional electron microscopy, cryo-electron tomography, and sub-tomogram analysis revealed RSs of various altered morphologies that, unexpectedly, differed between the two RS species. This indicates that HSP40 locks the RS into a functionally rigid conformation, facilitating its interactions with the adjacent central pair apparatus for transducing locally varied mechanical feedback, which permits rhythmic beating. Missing HSP40, like missing RSs, could be restored in a tip-to-base direction when HSP40 mutants fused with a HSP40 donor cell. However, without concomitant de novo RS assembly, the repair was exceedingly slow, suggesting HSP40/RS-coupled intraflagellar trafficking and assembly. Biochemical analysis and modeling uncovered spoke HSP40’s cochaperone traits. On the basis of our data, we propose that HSP40 accompanies its client RS precursor when traveling to the flagellar tip. Upon arrival, both refold in concert to assemble into the mature configuration. HSP40’s roles in chaperoning and structural maintenance shed new light on its versatility and flagellar biology.
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Marshall, Wallace F. "Quantitative High-Throughput Assays for Flagella-Based Motility in Chlamydomonas Using Plate-Well Image Analysis and Transmission Correlation Spectroscopy." Journal of Biomolecular Screening 14, no. 2 (February 2009): 133–41. http://dx.doi.org/10.1177/1087057108328131.
Full textAbstract:
Cilia are motile and sensory organelles with important roles in human development, physiology, and disease. Genetic defects in cilia produce a host of disease symptoms, including polycystic kidney disease, hydrocephalus, retinal degeneration, chronic bronchiectasis, infertility, and polydactyly. Currently, there are no known drugs for pharmacological remediation of ciliary defects. Small-molecule modulators of ciliary assembly or function would provide potential lead compounds for drug discovery efforts and would immediately be invaluable tools for a chemical biology approach to studying cilia. Here the author describes 2 assays for ciliary motility that are quantitative, automatable, cost-effective, and simple to implement. Both assays exploit cell-based strategies using the model organism Chlamydomonas reinhardtii. The first assay scores cilia-dependent gravitaxis by analyzing the cell distribution in wells of U-bottom microplates, using a simple and robust image analysis algorithm. The second assay measures motility directly by estimating the time required for cells to swim across a small illuminated aperture using a method equivalent to fluorescence correlation spectroscopy adapted to transmitted-light microscopy. The 2 assays have different advantages in terms of speed and sensitivity to small reductions in motility and may be most efficiently used in combination. ( Journal of Biomolecular Screening 2009:133-141)
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Walther, Z., M. Vashishtha, and J. L. Hall. "The Chlamydomonas FLA10 gene encodes a novel kinesin-homologous protein." Journal of Cell Biology 126, no. 1 (July 1, 1994): 175–88. http://dx.doi.org/10.1083/jcb.126.1.175.
Full textAbstract:
Many genes on the uni linkage group of Chlamydomonas affect the basal body/flagellar apparatus. Among these are five FLA genes, whose mutations cause temperature-sensitive defects in flagellar assembly. We present the molecular analysis of a gene which maps to fla10 and functionally rescues the fla10 phenotype. Nucleotide sequencing revealed that the gene encodes a kinesin-homologous protein, KHP1. The 87-kD predicted KHP1 protein, like kinesin heavy chain, has an amino-terminal motor domain, a central alpha-helical stalk, and a basic, globular carboxy-terminal tail. Comparison to other kinesin superfamily members indicated striking similarity (64% identity in motor domains) to a mouse gene, KIF3, expressed primarily in cerebellum. In synchronized cultures, the KHP1 mRNA accumulated after cell division, as did flagellar dynein mRNAs. KHP1 mRNA levels also increased following deflagellation. Polyclonal antibodies detected KHP1 protein in Western blots of purified flagella and axonemes. The protein was partially released from axonemes with ATP treatment, but not with AMP-PNP. Western blot analysis of axonemes from various motility mutants suggested that KHP1 is not a component of radial spokes, dynein arms, or the central pair complex. The quantity of KHP1 protein in axonemes of the mutant fla10-1 was markedly reduced, although no reduction was observed in two other uni linkage group mutants, fla9 and fla11. Furthermore, fla10-1 was rescued by transformation with KHP1 genomic DNA. These results indicate that KHP1 is the gene product of FLA10 and suggest a novel role for this kinesin-related protein in flagellar assembly and maintenance.
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Weng, Mingxiang, Yanwei Sha, Y. u. Zeng, Ningyu Huang, Wensheng Liu, Xinzong Zhang, and Huiliang Zhou. "Mutations in DNAH8 contribute to multiple morphological abnormalities of sperm flagella and male infertility." Acta Biochimica et Biophysica Sinica 53, no. 4 (March 11, 2021): 472–80. http://dx.doi.org/10.1093/abbs/gmab013.
Full textAbstract:
Abstract Asthenoteratospermia is an important cause of male infertility. Here, we report two infertile patients with severe asthenoteratospermia accompanied by new genetic abnormality. Whole-exome sequencing and bioinformatics analysis suggested that compound heterozygous mutations in DNAH8 (MIM:603337) may be responsible for multiple morphological abnormalities of the sperm flagella (MMAF). Immunofluorescence assay showed that DNAH8 protein expression was significantly decreased in the sperm tail of the patients, and electron microscopy exhibited an abnormal flagellum ultrastructure, while clinical pregnancy could be achieved by intracytoplasmic sperm injection. Therefore, the compound heterozygous mutations in the DNAH8 gene may be responsible for MMAF.
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Yang, P., L. Fox, R. J. Colbran, and W. S. Sale. "Protein phosphatases PP1 and PP2A are located in distinct positions in the Chlamydomonas flagellar axoneme." Journal of Cell Science 113, no. 1 (January 1, 2000): 91–102. http://dx.doi.org/10.1242/jcs.113.1.91.
Full textAbstract:
We postulated that microcystin-sensitive protein phosphatases are integral components of the Chlamydomonas flagellar axoneme, positioned to regulate inner arm dynein activity. To test this, we took a direct biochemical approach. Microcystin-Sepharose affinity purification revealed a prominent 35-kDa axonemal protein, predicted to be the catalytic subunit of type-1 protein phosphatase (PP1c). We cloned the Chlamydomonas PP1c and produced specific polyclonal peptide antibodies. Based on western blot analysis, the 35-kDa PP1c is anchored in the axoneme. Moreover, analysis of flagella and axonemes from mutant strains revealed that PP1c is primarily, but not exclusively, anchored in the central pair apparatus, associated with the C1 microtubule. Thus, PP1 is part of the central pair mechanism that controls flagellar motility. Two additional axonemal proteins of 62 and 37 kDa were also isolated using microcystin-Sepharose affinity. Based on direct peptide sequence and western blots, these proteins are the A- and C-subunits of type 2A protein phosphatase (PP2A). The axonemal PP2A is not one of the previously identified components of the central pair apparatus, outer arm dynein, inner arm dynein, dynein regulatory complex or the radial spokes. We postulate PP2A is anchored on the doublet microtubules, possibly in position to directly control inner arm dynein activity.