Gene Expression And Function Analysis Of Rice Sulfate Transporter OsSultr2;1

Sulphur plays crucial roles in plant growth,and is an essential element for biosynthesis of amino acids,oligopeptides,protein,vitamins and cofactors,and a variety of secondary products.In plants,sulphur is mainly taken up in the inorganic sulfate from the soil.It was found that the plasma membrane-bound sulfate transporters mediate the sulfate uptake of root from soil as well as the sulfate transfer between different plant organs and organelles,both of these two processes carry out in a cell membrane transport-across manner.Rice is one of important crops.Therefore, it is necessary to investigate the characteristics of sulfate transporters in rice and their regulation mechanism,which will give us new insight into understanding the roles of sulfur transporters in the development,output and quality of crops,and provide genetic resource for dealing with the problem of sulfur lacking in soil.Result of sequences alignment showed that there has high similarity between the OsSultr2:1 and members of group 2 of Arabidopsis thaliana sulfate transporter gene family.Phylogenetic analysis showed that Loc_Os03g09930 has the closest genetic relationship with AtSultr2;1 and AtSultr2;2,as suggested that Loc_Os03g09930 is a sulfate transporter of rice.Semi-quantitative RT-PCR results showed that the absence of sulphur resource increased the abundance of OsSultr2:1 mRNA both in root and shoot,and the mRNA abundances were linearly accumulated following the period of sulphur absence.Moreover,the expression of OsSultr2:1 showed negative correlation with the concentration of sulfate,and the abundance of OsSultr2;1 mRNA was gradually improved following the decrease in sulfate concentration in medium.The transient expression analysis of 35S:OsSultr2;1-GFP in onion epidermal cells using the gene gun transformation method indicated that the GFP signal of fused protein was mainly visualized on the plasma membrane,which suggested that OsSultr2;1 is a plasma membrane-localizing transporter.In order to elucidate the in vivo function of OsSultr2:1,we constructed a yeast recombinant expression vector through subcloning the coding region of OsSultr2:1 called pYE22m and transformed it into the yeast (Saccharomyces Cerevisiae) mutant CP154-7A with deficient sulfate transporting system for function complementation analysis.The results showed that under low concentration of sulfate condition,OsSultr2;1 was unable to complement the lesion of sulfate uptake activity in CP154-7A;on the contrary,under high concentration of sulfate condition,CP154-7A and its transform strain both grew.The results can not provide credible evidence to determine whether OsSultr2;1 act as sulfate transporter in rice,and more studies should be needed.