Transcriptome Profiling of Sulfur-Responsive Genes in Arabidopsis Reveals Global Effects of Sulfur Nutrition on Multiple Metabolic Pathways

Sulfate is a macronutrient required for cell growth and development. Arabidopsis has two high-affinity sulfate transporters (SULTR1;1 and SULTR1;2) that represent the sulfate uptake activities at the root surface. Sulfur limitation (-S) response relevant to the function of SULTR1;2 was elucidated in this study. We have isolated a novel T-DNA insertion allele defective in the SULTR1;2 sulfate transporter. This mutant, sel1-10, is allelic with the sel1 mutants identified previously in a screen for increased tolerance to selenate, a toxic analog of sulfate (Shibagaki et al., 2002). The abundance of SULTR1;1 mRNA was significantly increased in the sel1-10 mutant; however, this compensatory up-regulation of SULTR1;1 was not sufficient to restore the growth. The sulfate content of the mutant was 10% to 20% of the wild type, suggesting that induction of SULTR1;1 is not fully complementing the function of SULTR1;2 and that SULTR1;2 serves as the major facilitator for the acquisition of sulfate in Arabidopsis roots. Transcriptome analysis of approximately 8,000 Arabidopsis genes in the sel1-10 mutant suggested that dysfunction of the SULTR1;2 transporter can mimic general -S symptoms. Hierarchal clustering of sulfur responsive genes in the wild type and mutant indicated that sulfate uptake, reductive sulfur assimilation, and turnover of secondary sulfur metabolites are activated under -S. The profiles of -S-responsive genes further suggested induction of genes that may alleviate oxidative damage and generation of reactive oxygen species caused by shortage of glutathione.