The function of SULTR2;1 sulfate transporter during seed development in Arabidopsis thaliana

SULTR2;1 is a low-affinity sulfate transporter expressed in the vascular tissues of roots and leaves for interorgan transport of sulfate in Arabidopsis thaliana. Transgenic Arabidopsis carrying a fusion gene construct of SULTR2;1 5'-promoter region and beta-glucuronidase coding sequence (GUS) demonstrated that within the reproductive tissues, SULTR2;1 is specifically expressed in the bases and veins of siliques and in the funiculus, which connects the seeds and the silique. The antisense suppression of SULTR2;1 mRNA caused decrease of sulfate contents in seeds and of thiol contents both in seeds and leaves, as compared with the wildtype (WT). The effect of antisense suppression of SULTR2;1 on seed sulfur status was determined by introducing a sulfur-indicator construct, p35S::beta(SR)x3:GUS, which drives the expression of GUS reporter under a chimeric cauliflower mosaic virus 35S promoter containing a triplicate repeat of sulfur-responsive promoter region of soybean beta-conglycinin beta subunit (beta(SR)x3). The mature seeds of F1 plants carrying both the SULTR2;1 antisense and p35S::beta(SR)x3:GUS constructs exhibited significant accumulation of GUS activities on sulfur deficiency, as compared with those carrying only the p35S::beta(SR)x3:GUS construct in the WT background. These results suggested that SULTR2;1 is involved in controlling translocation of sulfate into developing siliques and may modulate the sulfur status of seeds in A. thaliana.