Genetic Interaction Of OsMADS1, OsMADS5, And OsMADS34 In Controlling Rice Floral Organ Identity And Development

Rice is one of the biggest flower plants in angiosperm. It evolves to have unique reproductive organ and flower morphology which is quite different to dicotyledon and other monocotyledon. And the morphogenesis and subsequent development of grasses reproductive organs would affect seeds production. Furthermore, the productions of rice is directly controlled by correct developmental process of reproductive organ and morphogenesis. Therefore, it’s theoretically important and practical to study the underlying molecular mechanism of flower development.In recent years, more and more genes in specifying rice floral organ identity and morphogenesis have been reported. But we still have little known about the molecular mechanism of E-class genes genetic interaction. Studies in model plants such as Arabidopsis showed that A、B、C、D and E function genes regulate floral organ development. Products of class E genes can interact with other MADS box proteins to form protein complexes. OsMADS1、OsMADS5、OsMADS34 are SEP-LIKE gene in rice and belong to E-class genes. This experiment adopts the method of genetics, biochemistry and molecular biology research of these three genes in the interaction mechanisms of rice floral organ development, and to get the following results:1. Using PCR-based reverse genetics approach, osmads5-3 mutant of OsMADS5was identified. Analysis of sequences flanking the T-DNA insertion revealed its insertion in the seventh intron of the OsMADS5 gene. Morphological observation showed that most of floral organs of osmads5-3 are normal, only anthers are slightly curved. Expression analysis demonstrates that OsMADS5 is expressed abundantly in spikelet and flower primordial, and carpel at stage sp6/8. It turned out that OsMADS5 may participate in the origination of spikelet and flower, and had a more important role in specifying carpel identity and development.2. On the basis of single mutant osmads5-3 and osmads1-2、osmads34-1, double mutants and triple mutant were constructed to research how interaction among OsMADS1、 OsMADS5、OsMADS34 to regulate rice floral organ development in the thesis by genetics and molecular biology research. Through observed the phenotype of mutants, it showed that OsMADS5 enhances the function of OsMADS1 to regulate the development of stamen and carpel redundantly; 0sMADS5 and OsMADS34 redundantly regulate lodicule identity, stamen and carpel meristem determinacy; OsMADS1,OsMADS5 and OsMADS34 determine floral organ identity.3. At the transcriptional level, we use QRT-PCR to analyze the relative expression of three genes in different mutants. It indicated that OsMADS1 could restrain the expression of OsMADS34, and the transcription of OsMADS1 was repressed by OsMADS34. In addition, OsMADS5 could promote the expression of OsMADS1 and OsMADS34 respectively.4. Through double yeast hybridization experiments, we analyze the interaction of the E-class genes in protein level. It showed that OsMADS34 could interact with OsMADS5, OsMADS7,OsMADS8 respectively in double yeast hybridization system. In addition,we detected that OsMADS5,OsMADS34,OsMADS2 could interact with each other,which suggested that those three protein could form protein complexes to regulate lodicule development. Similarly,OsMADS5, OsMADS34 and OsMADS2 might form protein complexes to determine the stamen meristem determinacy.