E2Fs Are Involved In The Mechanism Of Arabidopsis Reproductive Development Regulation

A number of cell fate determinations,including cell division,cell differentiation,and programmed cell death,intensely occur during plant germline development.How these cell fate determinations are regulated remains largely unclear.In the Arabidopsis genome,there are three kinds of E2 F family proteins.The transcription factor E2 F is a core cell cycle regulator.Here we show that the Arabidopsis canonical E2 Fs,including E2 Fa,E2Fb and E2 Fc,play an essential role in plant gametogenesis.The single mutants of e2 fa,e2fb,e2 fc and e2 fab,e2fac,e2 fbc double mutants are fertile.The e2 fa e2fb e2fc(e2fabc)triple mutant is sterile,although its vegetative development appears normal.These results suggested that canonica E2 Fs play a redundant and unique role in the plant fertility.On the one hand,the e2 fabc microspores undergo cell death during pollen mitosis.Microspores start to die at the bicellular stage.By the tricellular stage,the majority of the e2 fabc microspores are degenerated.On the other hand,a wild type ovule often has one megaspore mother cell(MMC),whereas the majority of e2 fabc ovules have two to three MMCs.The subsequent female gametogenesis of e2 fabc mutant is aborted and the vacuole is not formed in the embryo sac.Analysis of transmission efficiency showed that the canonical E2 Fs from both male and female gametophyte are essential for plant gametogenesis.Our study reveals that the canonical E2 Fs are required for plant gametogenesis,especially the pollen mitosis and the archesporial cell(AC)-MMC transition.