AtNSE1 and AtNSE3 are required for formation of embryo pattern and maintenance of cell viability during Arabidopsis embryogenesis

First author: Gang Li; Affiliations: Wuhan University (武汉大学): Wuhan, China

Corresponding author: Jie Zhao

Embryogenesis is an essential process during seed development in higher plant. Our previous work has showed that mutations of AtNSE1 or AtNSE3 would lead to early embryo abortion, and their proteins could interact with each other directly. However, the crucial regions of these proteins in this interaction, and how the proteins are cytologically involved in Arabidopsis embryo development are unknown. Here, we found that AtNSE1 can interact with the N-terminal of AtNSE3 by the C-terminal including the Ring-like motif, and only the Ring-like motif is essential for binding with three α motifs of AtNSE2/AtMMS21. Furthermore, by genetic assays and analyzing the molecular markers of cell fate decisions (STM, WOX5 and WOX8) in nse1 and nse3 embryos, we found that AtNSE1 and AtNSE3 worked non-redundantly in early embryo development, and the differentiation of apical meristem and the hypophysis was failed in the mutants which have disrupted auxin response and transportation. Besides that, the upper cells of suspensor in the mutants seem to have embryo proper cell identity. Cytological evidences showed that cell death occurred from early embryo stage, and the vacuolar programmed cell death and necrosis, occurred in nse1 and nse3 mutant embryos led to ovule aborted. As a result, AtNSE1 and AtNSE3 are essential for maintaining cell viability and growth during early embryogenesis. Our finding shed light on our understanding of the functions of SMC5/6 complex on early embryogenesis in Arabidopsis.

胚胎发生是高等植物种子发育过程中一个必不可少的过程。作者之前的研究显示AtNSE1和AtNSE3基因的突变会导致胚胎发生早期出现缺陷，并且这两个基因编码的蛋白可以直接相互作用。然而，这种相互作用的关键区域以及这两个蛋白如何参与拟南芥胚胎发生的还不清楚。本文中，作者发现AtNSE1可以通过其含有Ring-like基序的碳端与AtNSE3蛋白的氮端互作，并且AtNSE1的碳端仅有Ring-like基序对于其与AtNSE2/AtMMS21的三个α基序互作是必需的。此外，通过对nse1和nse3突变体胚胎的遗传学试验以及对于细胞命运决定的分子标记STM、WOX5和WOX8的分析显示，AtNSE1和AtNSE3基因在早期胚胎发生过程中发挥的作用并不冗余，并且突变体中顶端分生组织和胚根原的分化均失败，其生长素的响应和转运被扰乱。除此以外，突变体中胚柄的上层细胞似乎具有正确的胚胎细胞特征。细胞学证据显示突变体的胚胎发育早期就开始有细胞死亡，且液泡程序性死亡和组织坏死导致了胚珠败育。总的来说，AtNSE1和AtNSE3基因对于维持胚胎发育早期的细胞活力和生长至关重要。本文的研究加深了我们对于拟南芥中胚胎发生早期SMC5/6复合体功能的理解。

通讯：赵洁  (http://www.bio.whu.edu.cn/info/1191/4308.htm)

个人简介：1981年，华中师范大学，学士；1989年，华中师范大学，硕士；1999年，武汉大学，博士。

研究方向：被子植物有性生殖中授粉、受精和胚胎发育关键事态的分子机理，重点研究：1. 合子激活和定向分裂、早期胚胎启动和极性轴形成、胚胎细胞分化和器官建成等机制；2. 早期胚乳分裂和分化的分子机制；3. 花粉发育和花粉管定向生长机制，以及花粉与雌蕊的互作机制。

doi: https://doi.org/10.1093/jxb/erz373

Journal: Journal of Experimental Botany

Published date: August 13, 2019