Function of the sulfate transporter Sultr2;1 in seeds of Arabidopsis thaliana

Abstract

Arabidopsis thaliana has eleven putative sulfate transporter genes, many of which are expressed in a tissue specific manner. We made transgenic Arabidopsis plants (ATR2) carrying the antisense coding sequence of the low-affinity type sulfate transporter Sultr2;1 under the control of cauliflower mosaic virus (CaMV) 35S promoter. In this study, we characterized the role of Sultr2;1 in seeds using ATR2 transgenic lines.

As an indicator of sulfur status a chimeric promoter, comprising of the CaMV 35S promoter and a DNA fragment from the β subunit gene of soybean β-conglycinin, was fused to the gusA coding sequence (p35S-βββ-GUS) and introduced into Arabidopsis thaliana (Col-0, Awazuhara et al., in preparation). The promoter fragment used in this study was shown essential for the induction of the β subunit under sulfur starved condition. In this transgenic plant, GUS activity increased by sulfur starvation in aerial portions of plants.

In this study, we introduced p35S-βββ-GUS gene into ATR2 plants by genetic crossing. The mature seeds from the progenies carrying both the ATR2 and p35S-βββ-GUS constructs exhibited significant accumulation of GUS activities than those from the p35S-βββ-GUS plants. In seeds, the ratios of sulfate to nitrate concentrations were lower in ATR2 than in the wild type. However, concentrations of sulfate and nitrate were not affected by antisense suppression of Sultr2;1 in the rosette leaves of 3-week-old plants. From these results, we suggest that Sultr2;1 plays an important role in uptake of sulfate into seeds.