Cloning and characterization of two genes encoding sulfate transporters from rice (Oryza sativa L.)*

Abstract

Two genes were isolated from a rice genomic library and the coding region of their corresponding cDNAs generated by RT-PCR. These single copy genes, designated ORYsa; Sultr1; 1 and ORYsa; Sultr4; 1, encode putative sulfate transporters. Both genes encode proteins with predicted topologies and signature sequences of the H+/SO42- symporter family of transporters and exhibit a high degree of homology to other plant sulfate transporters. ORYsa; Sultr1; 1 is expressed in roots with levels of expression being strongly enhanced by sulfate starvation. In situ hybridization experiments revealed that ORYsa; Sultr1; 1 expression is localized to the main absorptive region of roots. This gene probably encodes a transporter that is responsible for uptake of sulfate from the soil solution. In contrast, ORYsa; Sultr4; 1 was expressed in both roots and shoots and was unresponsive to the sulfur status of the plant. The sequence of ORYsa; Sultr4; 1 contains a possible plastid-targeting transit peptide which may indicate a role in transport of sulfate to sites of sulfate reduction in plastids. The role of the transporter encoded by ORYsa; Sultr4; 1 is likely to be significantly different fromORYsa; Sultr1; 1. These are the first reports of isolation of genes encoding sulfate transporters from rice and provide a basis for further studies involving sulfate transport.