Functional Analysis Of Candidats Of PSD2, A Key Gene Controlling The Development Of Pistil And Stamen In Rice

Studies on dicotyledon flower development have made significant progress, but studies on monocotyledon flower development have comparatively lagged behind. Our laboratory found a rice mutant with completely degenerated staments and carpels (named as pistil stament degenration 2, psd2) by radiation mutation. By fine mapping, we localized the PSD2 gene in a 43.7 kb region between two microsatellite markers SSR24 and SSR29. Two genes encoding triacylglycerol lipases (named as Triacylglycerol lipase 1 and 2, TG1 and TG2) in this region were indentified as candidates of PSD2 by sequence analysis. On this basis, this study aimed to analyze the expression and function of the candidate genes of PSD2. The major results are as follows:1. Two available complementary vectors of TG1 and TG2 were used to transform rice. Ten TG1 transgenetic plants and 3 TG2 transgenetic plants with wild-type genetype were obtained, but no transgenetic plants with mutant genetype were acquired. At the same time, the two complementary vectors was also used to transform rice simultaneously, and one transgenetic plant carrying the two vectors was obtained. These transgenic plants are growing in the field and have not flowered. Therefore, their floral organ phenotypes cannot be observed at present. Furthermore, a vector of 35S::TG1 was also used to transform rice and 16 transgenic plants were acqired. By semi-quantitative RT-PCR, it was indicated that the expression of TG1 was upregulated in the transgentic plant, but the flower phenotype of the transgenic plant is the same as that of wild-type.2. A vector of pTG2::GUS was constructed and then used to transform rice. A 1228-bp promoter sequence of TG2 was amplified by PCR, and then integrated into pCAMBIA1391Z after digested with Sac I and Smal I. The vector was used to transform rice, and 12 transgenetic plants were obtained. These transgenic plants were transplanted onto the field, which have not flowered yet and therefore are not available for GUS staining.3. The expression levels of the two candidate genes of PSD2 in the different positions of psd2 mutant were investigated by semi-quantitative RT-PCR. The results indicated that the expression level of TG1 was higher than that of TG2. The expression of TG1 in root and 0-1cm young panicles was stronger than that in leaf and 1-5cm young panicles. The expression of TG2 in root, panicle and leaf was weak. The expression of TG2 in 0-1cm young panicles is stronger than in other positions.4. The expression of floral MADS-box genes in young panicles (0.5-1cm) of psd2 mutant and wild type was examined by semi-quantitative RT-PCR. The results showed that the expression of one class A gene (OsMADS15 ) was uprgulated, and that of five genes, including two class B genes (OsMADS4/16), two class C genes (OsMADS3/58) and one class E gene (OsMADS7), was downregulated in the mutant. The other genes had no obvious expression changes in the mutant. These changes of expression level are consistent with the phenotype of psd2 mutant. Key words: PSD2 floral organ development vector construction...