The Canonical E2Fs Are Required for Germline Development in Arabidopsis.

Shui Wang,Yingxiu Zhu,Teng Song,Huidan Yang,Zhongnan Yang,Jingshi Xue,Tianhua Wang,Xiaozhen Yao

doi:10.3389/fpls.2018.00638

Abstract

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. The transcription factor E2F is a core cell cycle regulator. Here we show that the Arabidopsis canonical E2Fs, including E2Fa, E2Fb, and E2Fc, play a redundant role in plant germline development. The e2fa e2fb e2fc (e2fabc) triple mutant is sterile, although its vegetative development appears normal. On the one hand, the e2fabc microspores undergo cell death during pollen mitosis. Microspores start to die at the bicellular stage. By the tricellular stage, the majority of the e2fabc microspores are degenerated. On the other hand, a wild type ovule often has one megaspore mother cell (MMC), whereas the majority of e2fabc ovules have two to three MMCs. The subsequent female gametogenesis of e2fabc mutant is aborted and the vacuole is severely impaired in the embryo sac. Analysis of transmission efficiency showed that the canonical E2Fs from both male and female gametophyte are essential for plant gametogenesis. Our study reveals that the canonical E2Fs are required for plant germline development, especially the pollen mitosis and the archesporial cell (AC)-MMC transition.

Highlights

Plant germline development, includes sporogenesis and gametogenesis, begins with the differentiation of a spore mother cell which produces haploid gametes through meiosis and mitosis (Schmidt et al, 2015)
We found that two amino acids, glutamate at 261 and asparagine at 272 in Arabidopsis E2Fa protein, were highly conserved in DBD1 (Figure 1B and Supplementary Figure S1)
The G1-S phase transition is controlled by the CDKRB-E2F core cell cycle signaling pathway (Polager and Ginsberg, 2009)

Summary

Introduction

Includes sporogenesis and gametogenesis, begins with the differentiation of a spore mother cell which produces haploid gametes through meiosis and mitosis (Schmidt et al, 2015). Plant haploid spores undergo two (for sperm) or three (for egg) rounds of mitoses to form a multicellular gametophyte. These processes involve a number of cell fate determinations including cell division, cell differentiation and programmed cell death (PCD) (Drews and Yadegari, 2002; Berger and Twell, 2011; Daneva et al, 2016).

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Conclusion