Biomedical subjects

Gregory J Taylor

Publications and source records attributed to Gregory J Taylor.

6 recordsLinked to original sources

PubMed2004

Large-scale identification of tubulin-binding proteins provides insight on subcellular trafficking, metabolic channeling, and signaling in plant cells.

Microtubules play an essential role in the growth and development of plants and are known to be involved in regulating many cellular processes ranging from translation to signaling. In this article, we describe the proteomic characterization of Arabidopsis tubulin-binding proteins that were purified using tubulin affinity chromatography. Microtubule co-sedimentation assays indicated that most, if not all, of the proteins in the tubulin-binding protein fraction possessed microtubule-binding activity. Two-dimensional gel electrophoresis of the tubulin-binding protein fraction was performed, and 86 protein spots were excised and analyzed for protein identification. A total of 122 proteins were identified with high confidence using LC-MS/MS. These proteins were grouped into six categories based on their predicted functions: microtubule-associated proteins, translation factors, RNA-binding proteins, signaling proteins, metabolic enzymes, and proteins with other functions. Almost one-half of the proteins identified in this fraction were related to proteins that have previously been reported to interact with microtubules. This study represents the first large-scale proteomic identification of eukaryotic cytoskeleton-binding proteins, and provides insight on subcellular trafficking, metabolic channeling, and signaling in plant cells.

Arabidopsis↗

PubMed2004

Maintaining exponential growth, solution conductivity, and solution pH in low-ionic-strength solution culture using a computer-controlled nutrient delivery system.

Studies of plant nutrient requirements in solution culture have often used nutrient concentrations many-fold higher than levels found in fertile soils, creating an artificial rooting environment that can alter patterns of nutrient acquisition. The relative addition rate (RAR) technique addresses this problem by providing nutrients in exponentially increasing quantities to plant roots in solution culture. A computer-controlled RAR nutrient delivery system has been developed to reduce workload and to facilitate more frequent nutrient additions (4x daily) than is possible with manual additions. In initial experiments, a minimum background solution containing 500 microM nitrogen and all other essential nutrients in optimal proportions was required for the healthy growth of Triticum aestivum. This requirement was reduced to 50 microM nitrogen when calcium in the background solutions was increased to 400 microM. Varying the abundance of ammonium and nitrate in both background and delivery solutions provided a means of controlling plant-induced pH changes in growth solutions. In optimized solutions, plant relative growth rates (RGR) in the order of 0.2 g g(-1) plant d(-1) were maintained over a 22 d experimental period. Variation in RARs provided a means of growing plants with varying RGRs under relatively constant conditions of solution electrical conductivity and pH.

Computers↗

PubMed2004

Complementation of Saccharomyces cerevisiae ccc2 mutant by a putative P1B-ATPase from Brassica napus supports a copper-transporting function.

Copper transport across membranes plays an important role in plant growth and survival. P(1B)-type ATPases participate in transmembrane transport of copper in various organisms. A Brassica napus cDNA (BnRAN1) encoding a putative Cu(2+)-ATPase was cloned in this study. A complementation assay demonstrated that the protein encoded by this cDNA could functionally replace Ccc2p, a Saccharomyces cerevisiae Cu(2+)-ATPase, rescuing growth of ccc2 mutant under iron-limited conditions. Our results suggest that this rescue likely resulted from restoration of copper delivery, mediated by BnRAN1, to Fet3p. This study is amongst the first to demonstrate that a putative plant P(1B)-ATPase is functional and to examine its substrate specificity.

Adenosine Triphosphatases↗

PubMed2004

Cadmium uptake and translocation in seedlings of near isogenic lines of durum wheat that differ in grain cadmium accumulation.

BACKGROUND: Cadmium (Cd) concentrations in durum wheat (Triticum turgidum L. var durum) grain grown in North American prairie soils often exceed proposed international trade standards. To understand the physiological processes responsible for elevated Cd accumulation in shoots and grain, Cd uptake and translocation were studied in seedlings of a pair of near-isogenic durum wheat lines, high and low for Cd accumulation in grain. RESULTS: In short-term studies (<3 h) using 109Cd-labelled nutrient solutions, there were no differences between lines in time- or concentration-dependent 109Cd accumulation by roots. In contrast, rates of 109Cd translocation from roots to shoots following longer exposure (48-60 h) were 1.8-fold higher in the high Cd-accumulating line, despite equal whole-plant 109Cd accumulation in the lines. Over the same period, the 109Cd concentration in root-pressure xylem exudates was 1.7 to 1.9-fold higher in the high Cd-accumulating line. There were no differences between the lines in 65Zn accumulation or partitioning that could account for the difference between lines in 109Cd translocation. CONCLUSION: These results suggest that restricted root-to-shoot Cd translocation may limit Cd accumulation in durum wheat grain by directly controlling Cd translocation from roots during grain filling, or by controlling the size of shoot Cd pools that can be remobilised to the grain.

Biological Transport↗

PubMed2003

Modulation of citrate metabolism alters aluminum tolerance in yeast and transgenic canola overexpressing a mitochondrial citrate synthase.

Aluminum (Al) toxicity is a major constraint for crop production in acid soils, although crop cultivars vary in their tolerance to Al. We have investigated the potential role of citrate in mediating Al tolerance in Al-sensitive yeast (Saccharomyces cerevisiae; MMYO11) and canola (Brassica napus cv Westar). Yeast disruption mutants defective in genes encoding tricarboxylic acid cycle enzymes, both upstream (citrate synthase [CS]) and downstream (aconitase [ACO] and isocitrate dehydrogenase [IDH]) of citrate, showed altered levels of Al tolerance. A triple mutant of CS (Deltacit123) showed lower levels of citrate accumulation and reduced Al tolerance, whereas Deltaaco1- and Deltaidh12-deficient mutants showed higher accumulation of citrate and increased levels of Al tolerance. Overexpression of a mitochondrial CS (CIT1) in MMYO11 resulted in a 2- to 3-fold increase in citrate levels, and the transformants showed enhanced Al tolerance. A gene for Arabidopsis mitochondrial CS was overexpressed in canola using an Agrobacterium tumefaciens-mediated system. Increased levels of CS gene expression and enhanced CS activity were observed in transgenic lines compared with the wild type. Root growth experiments revealed that transgenic lines have enhanced levels of Al tolerance. The transgenic lines showed enhanced levels of cellular shoot citrate and a 2-fold increase in citrate exudation when exposed to 150 micro M Al. Our work with yeast and transgenic canola clearly suggest that modulation of different enzymes involved in citrate synthesis and turnover (malate dehydrogenase, CS, ACO, and IDH) could be considered as potential targets of gene manipulation to understand the role of citrate metabolism in mediating Al tolerance.

Aluminum↗

PubMed2002

Vacuolar H(+)-ATPase, but not mitochondrial F(1)F(0)-ATPase, is required for NaCl tolerance in Saccharomyces cerevisiae.

Salt tolerance in Saccharomyces cerevisiae is a complex trait, involving regulation of membrane polarization, Na(+) efflux and sequestration of Na(+) in the vacuole. Since transmembrane transport energized by H(+)-adenosine triphosphatases (ATPases) is common to all of these tolerance mechanisms, the objective of this study was to characterize the responses of the plasma membrane H(+)-ATPase, vacuolar H(+)-ATPase and mitochondrial F(1)F(0)-ATPase to NaCl stress. We hypothesized that since the vacuolar ATPase is responsible for generating the proton motive force required for import of cations (such as Na(+)) into the vacuole, strains lacking this activity should be hypersensitive to NaCl. We found that strains lacking vacuolar ATPase activity were in fact hypersensitive to NaCl, while strains lacking ATP synthase were not. This effect was specific to the ionic component of NaCl stress, since the mutant strains were indistinguishable from wild-type and complemented strains in the presence of sorbitol.

Mitochondrial Proton-Translocating ATPases↗