Аннотация:Summary Cytokinin is an adenine derivative plant hormone that generally regulates plant cell division and differentiation in conjunction with auxin. We report that a major cue for the negative regulation of sulfur acquisition is executed by cytokinin response 1 (CRE1)/wooden leg (WOL)/ Arabidopsis histidine kinase 4 (AHK4) cytokinin receptor in Arabidopsis root. We constructed a green fluorescent protein (GFP) reporter system that generally displays the expression of the high‐affinity sulfate transporter SULTR1;2 in Arabidopsis roots. GFP under the control of SULTR1;2 promoter showed typical sulfur responses that correlate with the changes in SULTR1;2 mRNA levels; accumulation of GFP was induced by sulfur limitation (−S), but was repressed in the presence of reduced sulfur compounds. Among the plant hormones tested, cytokinin significantly downregulated the expression of SULTR1;2 . SULTR1;1 conducting sulfate uptake in sultr1;2 mutant was similarly downregulated by cytokinin. Downregulation of SULTR1;1 and SULTR1;2 by cytokinin correlated with the decrease in sulfate uptake activities in roots. The effect of cytokinin on sulfate uptake was moderated in the cre1‐1 mutant, providing genetic evidence for involvement of CRE1/WOL/AHK4 in the negative regulation of high‐affinity sulfate transporters. These data demonstrated the physiological importance of the cytokinin‐dependent regulatory pathway in acquisition of sulfate in roots. Our results suggested that two different modes of regulation, represented as the −S induction and the cytokinin‐dependent repression of sulfate transporters, independently control the uptake of sulfate in Arabidopsis roots.
