Abstract
During sulfur starvation, the induction of sulfate uptake is associated with the increase of mRNA abundance of sulfate transporters. In addition, N and C status are reported to control sulfate uptake. Though phytohormons elicit critical cues for the regulation of nitrate and phosphate acquisition, their roles in sulfate uptake have not been investigated. In Arabidopsis, two high-affinity sulfate transporters SULTR1;1 and SULTR1;2 expressed in root epidermis and cortex contribute to the uptake of sulfate. We tested the effects of phytohormons on SULTR1;2 expression. Among the number of phytohormons, cytokinin significantly down-regulated the accumulation of SULTR1;2. Sulfate uptake was down-regulated by cytokinin, and the rate of down-regulation was moderated in cre1-1 mutant. The cytokinin dependent-regulation of the counterpart transporter, SULTR1;1, was proved in sultr1;2 knockout plants. However, the response of SULTRs to the external sulfur status was similar between Ler and cre1-1, suggesting that sulfur and cytokinin independently regulate sulfate uptake.
