Littérature scientifique sur le sujet « OsSULTR »

Abstract Phloem loading is the first step in sucrose transport from source leaves to sink organs. The phloem loading strategy in rice remains unclear. To determine the potential phloem loading mechanism in rice, yeast invertase (INV) was overexpressed by a 35S promoter specifically in the cell wall to block sugar transmembrane loading in rice. The transgenic lines exhibited obvious phloem loading suppression characteristics accompanied by the accumulation of sucrose and starch, restricted vegetative growth and decreased grain yields. The decreased sucrose exudation rate with p-chloromercuribenzenesulfonic acid (PCMBS) treatment also indicated that rice actively transported sucrose into the phloem. OsSUT1 (SUCROSE TRANSPORTER 1) showed the highest mRNA levels of the plasma membrane-localized OsSUTs in source leaves. Cross sections of the OsSUT::GUS transgenic plants showed that the expression of OsSUT1 and OsSUT5 occurred in the phloem companion cells. Rice ossut1 mutants showed reduced growth and grain yield, supporting the hypothesis of OsSUT1 acting in phloem loading. Based on these results, we conclude that apoplastic phloem loading plays a major role in the export of sugar from rice leaves.

Being an essential macroelement, sulfur (S) is pivotal for plant growth and development, and acute deficiency in this element leads to yield penalty. Since the last decade, strong evidence has reported the regulatory function of silicon (Si) in mitigating plant nutrient deficiency due to its significant diverse benefits on plant growth. However, the role of Si application in alleviating the negative impact of S deficiency is still obscure. In the present study, an attempt was undertaken to decipher the role of Si application on the metabolism of rice plants under S deficiency. The results showed a distinct transcriptomic and metabolic regulation in rice plants treated with Si under both short and long-term S deficiencies. The expression of Si transporters OsLsi1 and OsLsi2 was reduced under long-term deficiency, and the decrease was more pronounced when Si was provided. The expression of OsLsi6, which is involved in xylem loading of Si to shoots, was decreased under short-term S stress and remained unchanged in response to long-term stress. Moreover, the expression of S transporters OsSULTR tended to decrease by Si supply under short-term S deficiency but not under prolonged S stress. Si supply also reduced the level of almost all the metabolites in shoots of S-deficient plants, while it increased their level in the roots. The levels of stress-responsive hormones ABA, SA, and JA-lle were also decreased in shoots by Si application. Overall, our finding reveals the regulatory role of Si in modulating the metabolic homeostasis under S-deficient condition.

OsSUT1 encodes a rice sucrose transport protein that is highly expressed in developing grain, leaf sheath and stem after heading, and in germinating seedlings, but only at very low levels in source leaves. In this study, we have used antisense gene suppression to elucidate the in vivo function of OsSUT1. Rice was transformed with an antisense construct containing a portion of the 3′-coding and non-coding regions of OsSUT1 driven by the maize ubiquitin-1 promoter. Twenty-six independent stably transformed lines were obtained. T0 and selfed T1 progeny were analysed for suppression of OsSUT1 expression and function. Many of the plants showed a significant reduction in their ability to produce filled grain, and final grain weight was reduced. Severe phenotypes correlated with a reduction in OsSUT1 transcript level in filling grain. Unlike SUT1 antisense suppression in dicots, source supply of photosynthate was unaffected in these transformants. This provides the first direct evidence for the requirement of a sucrose transporter for grain filling in a cereal species. Furthermore, seed from some of the T0 population showed a reduction in the rate of germination and growth, supporting the hypothesis that OsSUT1 may also play a role in transporting sucrose remobilized from starch reserves in germinating seeds.

We previously reported the cloning and tissue-specific expression of a gene encoding a sucrose/proton symporter in rice (Oryza sativa L.), OsSUT1 (Hirose et al. 1997, Plant Cell Physiology38, 1389–1396). This gene is expressed at high levels in the filling grain, leaf sheath and stem. Expression in these tissues occurred only after heading i.e. during the development of the reproductive structure as a major sink. In this paper, we report localisation of the transcript and protein to specific cells in the filling rice grain by in situ hybridisation with a probe from theOsSUT1 cDNA, and immunolocalisation of OsSUT1 and proton-pumping ATPase (H+-ATPase). An OsSUT1 cDNA probe recognises a transcript of approximately 2.4 kb, and the SUT1 antibody recognises a protein of approximately 55 kDa in total membrane protein extracts from the filling grain, leaf sheath and stem. In the developing grain, OsSUT1 is expressed at low levels before heading, with expression reaching a peak approximately ten days after emergence of the panicle from the sheath. Transcript is then present throughout seed development, with expression falling substantially after about 25 days post-heading. Both transcript and protein are localised to the aleurone cells of the developing grain, and are also detected in the maternal tissue, particularly the nucellus, vascular parenchyma tissue and the nucellar projection. Tissue slices from filling rice grain showed high rates of sucrose uptake that were inhibited by pCMBS. The role of OsSUT1 in sucrose transport to the filling grain endosperm is discussed.

The regulatory mechanisms of pollen development have potential value for applications in agriculture, such as better understanding plant reproductive regularity. Pollen-specific promoters are of vital importance for the ectopic expression of functional genes associated with pollen development in plants. However, there is a limited number of successful applications using pollen-specific promoters in genetic engineering for crop breeding and hybrid generation. Our previous work led to the identification and isolation of the OsSUT3 promoter from rice. In this study, to analyze the effects of different putative regulatory motifs in the OsSUT3 promoter, a series of promoter deletions were fused to a GUS reporter gene and then stably introduced into rice and Arabidopsis. Histochemical GUS analysis of transgenic plants revealed that p385 (from −385 to −1) specifically mediated maximal GUS expression in pollen tissues. The S region (from −385 to −203) was the key region for controlling the pollen-specific expression of a downstream gene. The E1 (−967 to −606), E2 (−202 to −120), and E3 (−119 to −1) regions enhanced ectopic promoter activity to different degrees. Moreover, the p385 promoter could alter the expression pattern of the 35S promoter and improve its activity when they were fused together. In summary, the p385 promoter, a short and high-activity promoter, can function to drive pollen-specific expression of transgenes in monocotyledon and dicotyledon transformation experiments.

Sulfur (S) is an essential macronutrient required by plants for their correct development. This element is fundamental for the biosynthesis of different compounds, such as the two amino acids, cysteine (Cys) and methionine (Met), vitamins (biotin and thiamine), peptides involved in the response to abiotic stresses (glutathione - GSH, and phytochelatines - PCs), lipids and co-factors. Sulfate (SO42-) is the main S form taken up from soil by root system and then assimilated inside the cells during the sulfur reductive pathway. The uptake and the systemic movements of this anion are accomplished by the SULfate TRansporter (SULTR) gene family, which encode for H+/SO42- membrane co-transporters with different localization, amino acidic sequences, and affinity to sulfate. Since has been demonstrated that S has a key role in the response to different abiotic stresses (such as sulfur deficiency, heavy metal exposure or salt stress), the expression of these genes must be finely regulated, according to the different environmental conditions and requests for S reduced compounds. The general aim of the present thesis is the description of S systemic fluxes in rice in different stress conditions, to obtain more information about the contribution of S in determining plant tolerance to abiotic stresses. To achieve the goal, we also took advantage of analysis performed with an elemental analyzer coupled with an isotope ratio mass spectrometer (EA-IRMS), a powerful instrument which utilizes stable isotopes of elements as tracers. The entire research has been divided in three different parts. In the first work, potential 32S/34S isotope effects occurring during SO42- uptake were investigated in a closed hydroponic system in which a limited amount of substrate (SO42- in the nutrient solution) was continuously removed from the solution by the activity of the sulfate transporters of the root and converted in a final product (total S of the plant). An isotope discrimination against 34S occurred during SO42- uptake: plants had a lighter S isotope composition, and the residual SO42- in the hydroponic solution was enriched in heavy stable isotope. Fractionation during uptake showed two phases characterized by different fractionation factors, reflecting changes in the expression of the OsSULTR deputed to the root uptake which may explain the different isotope phenotypes observed during plant sulfate acquisition. Moreover, the possible 32S/34S isotope effects associated to both S partitioning and metabolism were investigated by comparing plants pre-grown in complete nutrient solutions and then continuously maintained on media containing SO42- (steady-state) or deprived of SO42- for 72h. The SO42- pool of the steady-state shoot was significantly 32S depleted with respect to the SO42- pools of root, while the organic S (Sorg) pools were significantly depleted in 34S compared to both the SO42- pool of both the organs and the S source. These results suggested a higher S assimilation in the aerial part of plants which favor the lighter isotope. Under S starvation, S assimilation progressively enriched the Sorg pools in the lighter 32S isotope and the residual SO42- in both the organs in the heavier 34S isotope. Most pronounced isotope separations were again observed in the shoot, confirming the prominent role of this organ in SO42- assimilation and S allocation. No fractionation due to translocation activity was observed. In the second part of the work, to validate the results previously obtained, we performed a mass balance study in rice plants exposed for 72h to different Cd concentrations, to investigate possible changes in S stable isotope fractionation due to this stress: in fact, adaptation of S metabolism has a pivotal role in responses to heavy metal exposure. As expected, Cd treatment strongly enhanced SO42- uptake and assimilation, as indicated by the analyses of the S pools (Stot, SO42-, and Sorg). S isotope analyses performed on the whole plants revealed changes in the S metabolism associated to variations in the discrimination against 34S, which was less evident as Cd concentration in the external medium increased. Transcriptional analysis suggested again that change of the ratio between relative transcripts of OsSULTR1;1 and OsSULTR1;2, as observed for S starvation, may be responsible for the progressive decreased in 34S isotope discrimination. The important role of shoot in S assimilation was confirmed: isotope fractionation associated to sulfate assimilation was higher in shoot than in root, and progressively increased as Cd concentration did. The last part of work was focused on fully characterize, under hydroponics-controlled conditions in the absence or in the presence of salt stress (80 mM NaCl), the phenotypic behavior in the already available salt tolerant introgression line (IL) Onice 11 (O11), obtained by Marker-Assisted Back-Cross (MABC) selection starting from the cross between the Italian japonica elite cultivars Onice (sensitive recurrent parent) and the indica variety IR64-SalTol (tolerant), donor of the major QTL SalTol. Moreover, S acquisition and metabolism of O11 and both the parental lines were evaluated to investigate their possible implication in determining the different tolerance to salt stress. Results showed the beneficial effect of the introgression of the SalTol QTL from the indica variety into selected japonica rice line, based on different characteristics of selected phenotypic-biochemical-physiological parameters. However, salt stress strongly affected S uptake and assimilation, and we can reasonably suppose that these features do not justify the different salt tolerance in the considered IL O11. In conclusions, rice plants can discriminate against 34S during SO42- uptake and assimilation. Between plants organs, shoot represents the predominant one involved in S assimilation. Abiotic stresses, such as S starvation or Cd exposure, lead to changes in the ratio of relative transcripts between the OsSULTRs involved in the uptake of sulfate, and this may be the cause of the different isotope phenotypes observed. Finally, salt tolerance in the IL O11 appears to not be dependent on different S metabolism.

碩士
國立臺灣大學
農藝學研究所
101
Plants are often suffered by wounding stresses caused by biotic and abiotic factors during growth and development, and they will modulate physiological and metabolic behavior to process repair and defense responses. Sugars play an important role to provide carbon and energy source for healing at wound site. The expression of OsSUT4 gene, one of rice sucrose transporter family member, was significantly enhanced by mechanical woundsing and Spodoptera litura chewing stimuli. However, when rice plants was attacked by sap-sucking pest, i.e. Nilaparvata lugens, OsSUT4 gene expression in rice culm was down-regulated. In addition to OsSUT4 expression, the transcript levels of the cell wall invertase gene (OsCIN1) and monosaccharide transporter gene (OsMST6) were also increased in mechanical wounding-treated rice plants. Expression of OsSUT4 can be promoted by exogenous jasmonate (JA) and ethylene. Furthermore, if JA biosynthesis pathway was blocked, the wound-induced OsSUT4 expression would be repressed. In addition, since NADPH oxidase inhibitor treatment can reduce the wounding effect on OsSUT4 expression, H2O2 was considered to function as a signal factor involved to the regulatory pathway of wound-regulated OsSUT4 expression. According to OsSUT4 promoter activity analysis in transgenic rice plants, it was suggested that the wounding-responsive element on OsSUT4 promoter was located at the region within 248 bp upstream of the translation start codon.

碩士
國立臺灣大學
農藝學研究所
103
Plants were often suffered from many biotic and abiotic stresses such as mechanical wounding and insect herbivores. Plants protect themselves by several defense responses. Sucrose is the major product of photosynthesis. It is involved in many metabolic regulatory pathways and plays an important role in the plant defense responses as signaling molecule. Rice leaffolder [Cnaphalocrocis medinalis (Guenée)] is one of chewing insects. It attacks rice plants by folding leaves and scraping the mesophyll tissues. In this study, we found that after fourth-instar larvae feeding, sucrose contents were decreased in the leaf damaged by leaffolder but increased in developing leaf. Thus, it was suggested that sucrose translocation from damaged leaf to developing sink tissues may be promoted in leaffolder-attacked rice plants. Sucrose transporters (SUT) is the key factor in charge of sucrose loading and unloading in phloem for long-distance translocation in plants. Gene expressions of OsSUT4, a rice SUT gene family member, were significantly induced in leaffolder infestated leaves, but the changes of transcript levels in other leaves were not significant. Rice leaffolder infestation induced jasmonic acid, salicylic acid, abscisic acid and ethylene biosynthesis gene expressions in rice seedlings. Hydrogen peroxide were also accumulated in wounded leaves. Furthermore, leaffolder-induced OsSUT4 gene expressions in leaf tissues would be repressed by inhibitors of jasmonic acid, abscisic acid and hydrogen peroxide biosynthesis. Taken together, the aforementioned results suggested that OsSUT4 gene expression induced by leaffolder infestation was mediated jasmonic acid, abscisic acid or hydrogen peroxide as signalings.

A prosthetic limb is an artificial device that replaces missing body part, or parts. Prosthetic limbs are used for many different applications however the application of prosthetic limbs focused in this paper categorized as prosthetic enhancements. Prosthetic enhancements are special prosthetic that allow the patients to participate in more rigorous recreational activities, such as running. These prosthetic limbs now have started to arise in major sporting events like the Olympics. Some researchers say that the legs use only 25% of the energy that an able bodied leg would use. High performance prosthetic running legs made of carbon fiber, show great advantages over their metal counterparts. Including being lighter and being able to retain more strain energy, current carbon fiber running blades offered by Ossur provide the best performance in the market. In this study, prosthetic racing legs known as blades were analyzed using finite element analysis technique. Performance improvements of these blades were sought by creating mechanical models of the current Ossur products using the finite element analysis software ANSYS and incorporating better performing composite materials into the mechanical simulations. Two different composite materials have taken in consideration by which the legs are created from, these are thermoplastic values for polyethylene epoxy and Vinylester. The use of a new composite material reduces the strain in each of the existing blade geometries, and it permits fewer layers of carbon fiber to be required in the construction of these running blades, which reduces the weight of each leg. Three different blade designs such as Cheetah blade, Flex-Run blade and Flex-Sprint blade have been considered in this study. Also two different loading conditions on the blade such as standing and running conditions have been considered.

Advanced prostheses are currently being sold in consumer markets. The development of these advanced prostheses is largely a result of a better understanding of the biomechanics of human locomotion [1]. Powered and microprocessor controlled prostheses are offering better performance in a variety of movements and in the gait cycle. However the focus in lower limb prosthetics has been largely on locomotion (e.g. walking, stair gait and running). This study focuses on the sit and stand cycles of an individual with an Otto Bock C-leg and an Ossur Power Knee prosthesis, comparing his ability to utilize each prosthesis and comparing his cycle to that of a healthy (non-amputee) control subject. This study is part of a larger ongoing study of the sit and stand cycles seen in a large population of unilateral transfemoral prosthetic users of various kinds. The purpose of this study is to compare the difference in method of standing, and assistance provided by the prosthesis. With the knowledge gained from this study we hope to better understand the biomechanics of the sit and stand cycles, leading to better prostheses in the future.

Previous studies have been conducted to develop a biomechanical model for a human’s lower limb. Amongst them, there have been several studies trying to quantify the kinetics and kinematics of lower-limb amputees through motion analysis [5, 10, 11]. Currently, there are various designs for lower-limb prosthetic feet such as the Solid Ankle Cushion Heel (SACH) from Otto Bock (Minneapolis) or the Flex Foot from Ossur (California). The latter is a prosthetic foot that allows for flexibility while walking and running. Special interest has been placed in recording the capabilities of these energy-storing prosthetic feet. This has been done through the creation of biomechanical models with motion analysis. In these previous studies the foot has been modeled as a single rigid-body segment, creating difficulties when trying to calculate the power dissipated by the foot [5, 20, 21]. This project studies prosthetic feet with energy-storing capabilities. The purpose is to develop an effective way of calculating power by using a biomechanical model. This was accomplished by collecting biomechanical data using an eight camera VICON (Colorado) motion analysis system including two AMTI (BP-400600, Massachusetts) force plates. The marker set that was used, models the foot using several segments, hence mimicking the motion the foot undergoes and potentially leading to greater accuracy. By developing this new marker set, it will be possible to combine the kinematic and kinetic profile gathered from it with previous studies that determined metabolic information. This information will allow for the better quantification and comparison of the energy storage and return (ES AR) feet and perhaps the development of new designs.

Regaining biomechanical function, comfort and quality of life is a prime consideration when designing prosthetic limbs. Recently, microprocessor-controlled prosthetic knees, which rely on magneto-rheological (MR) technology, have become available and have the potential to meet these needs. One of these promising products is a prosthetic knee manufactured by the company Ossur Inc. The knee is a synergy of artificial intelligence, advanced sensors and MR actuator technology. A critical factor in the success of the prosthetic knee is the composition of the MR fluid. In the prosthetic actuator, the fluid is used in shear mode in a micron-sized fluid gap. The characteristics of the MR fluid, such as, the off-state viscosity, the field-induced shear yield stress, the post-yield viscosity, and the particle sedimentation rate, determine the properties of the prosthetic knee. This paper describes a novel perfluorinated polyether (PFPE)-based MR fluid with properties that are tailored for the requirements of the prosthetic knee actuator. Rheological measurements of monodisperse and bidisperse PFPE-based fluid mixtures are presented. The monodisperse fluid consists of micron-sized carbonyl iron particles and the bidisperse mixture contains micron- and nano-sized particles. A few different concentrations of nano particles are investigated; first by holding the total solid concentration constant, and then by increasing the total solid concentration, to exceed that of the MR fluid containing only micron-sized particles. An MR fluid composition is sought that has a suitable balance between field-induced strength, off-state viscosity and sedimentation rate, for the proposed application. This balance is determined by desired qualities of the prosthetic knee and relate directly to the MR fluid. The field-induced shear stress of MR fluid samples is measured as a function of the magnetic flux density along with the off-state viscosity as a function of the shear-rate. The shear stress and off-state viscosity at high-shear rates are of particular interest, since the working shear rate in the prosthetic knee is high, due to the micron-sized gap between the blades in the fluid chamber of the actuator. Mathematical models are presented that describe how the MR fluid properties relate to the behavior of the prosthetic knee. The paper shows how a tailored design of an MR fluid can further the success of the MR prosthetic knee.