Quantitative Trait Loci For Mercury Tolerance In Rice Seedlings And Functional Analysis Of OsPP2C Gene Related To Mercury Tolerance

Mercury (Hg) pollution has become an environmental problem on a global scale. Hg2+is one of the most toxic heavy metals and has no known beneficial biological function. To investigate the mechanism of Hg2+tolerance, japonica rice Yuefu and IRAT109were used for QTL analysis;9311and Azucena were used for analyzing the function of OsPP2C gene. The results are summarized as follows:1. To estimate the Hg2+tolerance of Yuefu and IRAT109, a dose experiment was conducted. Four-day old seedlings were exposed to the solution containing0,0.5,1.0,1.5,2.0,2.5μM HgCl2for3d, and then the longest roots were measured. Relative root length (RRL) was used for evaluating the Hg2+tolerance. The results showed that Yuefu had the higher degree of Hg2+tolerance than IRAT109. There was a significant difference (P<0.01) in Hg2+tolerance between Yuefu and IRAT109only at the concentrations of1.0and1.5μM. And the largest difference occurred at the concentrations of1.5μM HgCl2.2. Recombinant inbred line (RIL) population of120lines derived from the cross between an Hg-tolerant variety Yuefu and an Hg-sensitive variety IRAT109were treated with1.5μM HgCl2for3d, and then the QTL analysis was done. Three QTLs for Hg2+tolerance were detected on chromosome1,2and5, and explained11.0%,10.8%and13.9%of the total phenotypic variance, respectively.3.15μM Hg2+was used for treating the seedlings of9311and Azucena. The results showed that the growth of rice seedlings was inhibited by Hg2+. Thus,9311was more tolerance to Hg2+stress than Azucena.4. Many studies have shown that protein phosphatase PP2Cs play an important role in the resistance to disease and to abiotic stress in plant. In this paper, the real-time quantitative PCR was used to analyze the expression of OsPP2C gene which was selected by our previous study in rice roots treated with Hg2+. The expression patterns varied in9311and Azucena. The expression of OsPP2C gene in9311was significantly higher than Azucena when treated with Hg2+for3h,6h, and9h.5. The recombinant plasmid containing OsPP2C gene was transformed into Escherichia coli for prokaryotic expression analysis. The effects of Hg2+on the growth of E. coli with empty vector pET24a and the recombinant plasmid pET24a-OsPP2C were compared. The results showed that the OsPP2C gene could enhance the tolerance of E. coli to Hg2+stress.