Functional Analysis Of Rice Sulfate Transporter Gene OsSultr1;1

Sulfur is an essential macronutrient for plants which, plays crucial roles in the process of growth regulation, detoxification, defence and response to various abiotic and biotic stresses, and is also required for the biosynthesis of several S-containing amino acids, proteins, vitamins and a variety of secondary metabolism products. Sulphate is the major form of sulphur that plants can absorb from the soil.Proton/sulphate co-transport which mediated by the group 1 high-affinity sulfate transporters in the plasma membrane of root cells is the first step for the uptake of sulphate from the environment.Rice is one of the most important food crops in the world, especially in China, and it has also become a model plant for monocot cereal genome research and molecular breeding, with the completion of whole genome sequencing and development of biotechnology. The characterization of sulfate transporters and a better understanding of their regulation mechanisms underlying sulfur inefficiency will be helpful for investigating the roles of sulfur nutrient in development, yield and quality of crops, and also will provide resource for genetic improvement of crops.In this work, the 1989bp of full-length cDNA sequence of OsSultrl;1 was cloned from rice root. Semi-quantitative RT-PCR analysis indicated that the OsSultrl;1 gene specifically expressed in the root of the plant and the absence of sulphur increased the expression of OsSultrl;1; the mRNA abundances showed linear relationship with the period of sulphur absence. Moreover, the expression of OsSultrl;1 showed negative correlation with the concentration of sulfate and the abundance of OsSultrl;1 mRNA was gradually increased following the decrease of sulfate concentration in medium. The transient expression analysis of Ubi:OsSultrl;1-GFP in onion epidermal cells using the biolistic bombardment transformation method indicated that the GFP signal of the fused protein was mainly visualized on the plasma membrane, which suggested that OsSultrl;1 is a plasma membrane-localizing transporter. In order to elucidate the in vivo function of OsSultrl;1, we constructed a yeast recombinant expression vector OsSultrl;1-pYE22m and transformed it into the yeast (Saccharomyces Cerevisiae) mutant CP154-7A which defects sulfate transporting system for functional complementation analysis. The results showed that OsSultrl;1 was able to complement the loss of sulfate uptake activity of CP154-7A under low sulfate concentration, which proved that OsSultrl;1 could act as a high affinity sulfate transporter in rice. We also constructed a OsSultrl;1 promoter-GUS expression vector for further exploration of the tissue localization of this protein.