Functional And Expressional Analysis Of Candidats Of PSD2,a Gene Regulating Floral Organ Development In Rice

The molecular mechanism of floral organ development is a hotspot in plant developmental biology researches. Our laboratory found a rice mutant with completely degenerated staments and carpels (named as pistil-stament degenration2, psd2) by radiation mutation. By fine mapping, we localized the PSD2gene in a43.7kb region between two microsatellite markers SSR24and SSR29. Two genes encoding triacylglycerol lipases (named as Triacylglycerol lipase1and2, TGI and TG2) in this region were indentified as candidates of PSD2by sequence analysis. Based on the above results, this study aimed to further study the function and expression of the candidate gene of PSD2by complementation test, GUS expression test, and RNA interference. The major results are as follows:(1) A complementary vector was constructed and used to transform embryo calli from PSD2heterozygote.2transgenic complement plants and7transgenic plants with PSD2PSD2/PSD2psd2genotype were obtained. The lodicules, stamens and capel were recovered normal in the transgenic complement plants, but an extra glume formed between empty glume and lemma. Semi-quantitative RT-PCR indicated that the expression of TG2in transgenic complement plants was weaker than that in wild type plant. The reason might be that the promoter sequence used in the complementary vector was not long enough, or the insertion site of the complementary vector was not quite appropriate, resulting in the expression of TG2not be able to reach the normal level. Other7transgenic plants did not produce seeds because of cold weather. Therefore, the phenotypes of their next generation could not be identified.(2) A GUS expression vector constructed by Ms. Gu Juntian was used to transform a japonica rice cultivar zhonghua15, and11transgenic plants were obtained. Staining results showed that TG2mRNA was detected in root and leaf, but not in shoot apical prior to reproductive transition. After the shoot apical was converted into inflorescence meristem, strong TG2expression was observed at the primary and secondary branch stages. In addition, TG2expression was also found in all the parts of a mature spikelet.(3) An RNA interference vector for TG1was constructed to transform zhonghua-11 and zhonghua-15, and12and25transgenic plants were obtained from the two cultivars, respectively. The flower phenotype of the transgenic plants was the same as that of wild type. Semi-quantitative RT-PCR indicated that the expression of TG1in the transgenic complement plants was not down-regulated, suggesting that the RNAi failed.