| Research Abstract |
To investigate the changes in profiles of mRNA accumulation in response to sulfur deficiency, Arabidopsis thaliana ESTS corresponding to approximately 8000 genes were analyzed using DNA macroarray. Three-week-old Arabidopsis plants grown on control medium were transferred to a sulfate-free medium and grown for 48 h for the analyses of sulfur-related metabolites and global gene exression profiles. Concentrations of sulfate, O-acetyl-L-serine (OAS), a positive regulator of sulfur deficiency-responsive genes, cysteine and glutathione (GSH) were determined. Macroarray analysis revealed a number of genes, including APR1 and sultr1 ; 2, whose mRNA accumulation was increased by sulfur deficiency. Profiling was also carried with plants treated with OAS under sulfate-sufficient condition. Scatter plot analysis revealed a positive correlation between the changes of expression levels by sulfur deficiency and by OAS treatment among the clones tested, suggesting that mRNA accumulation of a number o
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f genes under sulfur deficiency is mainly controlled by OAS concentrations in tissues. It was also revealed that the sets of genes regulated under sulfur deficiency in leaves and roots differ considerably. Plants reserve nitrogen and sulfur (S) as seed storage proteins (SSPs) for germination of next generation. Composition of SSPs changes according to sulfur availability in soil to maintain nitrogen contents in seeds. We examined the difference of protein accumulation patterns in Arabidopsis seeds harvested under S-deficient and control condition by proteome analysis. Several proteins increased under S-deficient condition. They were identified forms of the 12S SSPs, CRA1 and putative cruciferin. MALDI-TOFMS analyses showed the C-terminal processing did not occurred under S-deficient condition. Other proteins that increased under S deficiency were identified as a precursor of CRA1 and alpha-subunits of CRA1 and putative cruciferin whose isoelectric points were shifted. These results suggested SSPs undergo some different post-translational cleavages and modifications under S-deficient condition. Less
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