Functional And Expressional Analysis Of POS, A Gene Regulating Floral Organ Development In Rice

The molecular mechanism of floral organ development is a hotspot in plant developmental biology researches. Rice (Oryza sativa L.) is a model species of monocotyledons and the world's most important food crop as well. The outcome of rice floral organ development directly affects and decides the yield and the quality of rice. Therefore, understanding the molecular mechanism of floral organ development is very important. pos mutant was found from the progeny of young embryo tissue culture of indica cultivar Minghui-86. Using positional cloning approach, our laboratory had characterized the candidate gene of POS as a transcription factor encoding a C2H2 zinc-finger protein, closely homologous to Arabidopsis JAGGED (JAG). Based on the above results, this study aimed to further study the function and expression of the candidate gene of POS by complementation test, RNA interference, over-expression and GUS expression test .The major results are as follows:(1) A complementary vector constructed by Ms. Diao Zhijuan was used to transform young embryo calli from pos heterozygote, and 17 transgenic plants with POSpos genotype were obtained. The phenotype of mutants from the selfing progeny of these transgenic plants was recovered, confirming that the candidate gene is POS, encoding a C2H2 zinc-finger protein.(2) A GUS expression vector was constructed to transform Minghui-86 and 5 transgenic plants were obtained. Staining results showed that POS mRNA was detected in vegetative organs, including root, leaf, shoot apex, upper node and tiller. POS mRNA was also detected in reproductive organs. Weak expression of POS was found in lodicule, filament and carpel; high expression was found in lemma, palea, anther and style; the strongest expression was found in the boundary region between whorl 3 and whorl 4.(3) An RNA interference vector was constructed to transform three japonica cultivars, Nipponbare, zhonghua-11 and zhonghua-15, and 3 positive transgenic plants were obtained from Nipponbare. Moreover, 10 and 7 transgenic plants were obtained from zhonghua-11 and zhonghua-15, respectively. These transgenic plants have not been comfirmed whether they are positive or not because they are too weak for the test at present.(4) An over-expression vector constructed by Ms. Diao Zhijuan was used to transform young embryo calli from Minghui-86 and a lot of kanamycin-resistant calli were obtained. However, most of the kanamycin-resistant calli could not regenerate into seedlings after turning green, but turned brown and died. Only 2 transgenic plants were obtained. These 2 transgenic plants are still at the seedling stage and therefore cannot be investigated whether their flowers change or not.