Primary Study On Molecular Mechanism Of Floral Patterning In Lotus Japonicus

Floral pattern has drawn extensive attention from biologists. Floral pattern formation includes three stages, floral meristem formation, floral meristem partition/floral organ primordia initiation and floral organ identity determination. Molecular mechanisms controlling these stages have been identified based on the results from far related model systems, Antirrhinum and Arabidopsis. FLO/LFY and FIM/UFO are involved in floral meristem identity determination and transactivation of floral organ identity genes. ABC model has been successfully adapted to explain the floral organ identity determination in several species. In the view of evodevotics, the question is still remained. How did the floral pattern of all sorts arise? In other words, how much of the developmental machinery is conserved in most species and how much is special for unique floral form? We explore these questions in Legume model system , Lotus japonicus. Compared with model plants Antirrhinum and Arabidopsis, floral pattern formation of Lotus japonicus is different in several aspects. Floral organs initiate in an order of sepals, carpel, petals, stamens. Within each whorl, organs initiate unidirectionally from ventral side to dorsal side. Initiation of organs in different whorl overlaps. Stamens exist in both 2nd whorl and 3rd whorl, and 2nd whorl is heterogeneous for the existence of different identity organs (petals and stamens). There is a transient stage of petal-stamen common anlagen before petal and stamen primordia initiation. In this study we adopted two approaches to address this difference of floral pattern complexity. Firstly, we got four similar floral pattern defective mutants(SL1203,F0795,F0833 and F0951)by mutant library screening. They all show floral meristem proliferating and defects in petal and stamen ontogeny. Secondly, 13 orthologs of key genes in floral patterning have been isolated. And agrobacteria mediated...