State Key Laboratory of Hybrid Rice, College of Life Sciences, Wuhan University, Wuhan, China.
J Exp Bot. 2019 Nov 18;70(21):6229-6244. doi: 10.1093/jxb/erz373.
Embryogenesis is an essential process during seed development in higher plants. It has previously been shown that mutation of the Arabidopsis non-SMC element genes AtNSE1 or AtNSE3 leads to early embryo abortion, and their proteins can 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. In this study, we found that the C-terminal including the Ring-like motif of AtNSE1 can interact with the N-terminal of AtNSE3, and only the Ring-like motif is essential for binding with three α motifs of AtNSE2 (homologous to AtMMS21). Using genetic assays and by analysing molecular markers of cell fate decisions (STM, WOX5, and WOX8) in mutant nse1 and nse3 embryos, we found that AtNSE1 and AtNSE3 work non-redundantly in early embryo development, and that differentiation of the apical meristem and the hypophysis fails in the mutants, which have disrupted auxin transportation and responses. However, the upper cells of the suspensor in the mutants seem to have proper embryo cell identity. Cytological examination showed that cell death occurred from the early embryo stage, and that vacuolar programmed cell death and necrosis in the nse1 and nse3 mutant embryos led to ovule abortion. Thus, AtNSE1 and AtNSE3 are essential for maintaining cell viability and growth during early embryogenesis. Our results improve our understanding of the functions of SMC5/6 complex in early embryogenesis in Arabidopsis.
胚胎发生是高等植物种子发育过程中的一个重要过程。先前的研究表明，拟南芥非 SMC 元件基因 AtNSE1 或 AtNSE3 的突变会导致早期胚胎夭折，并且它们的蛋白质可以直接相互作用。然而，这些蛋白质在相互作用中的关键区域以及它们如何在细胞学上参与拟南芥胚胎发育尚不清楚。在本研究中，我们发现 AtNSE1 的 C 端（包括环状基序）可以与 AtNSE3 的 N 端相互作用，并且只有环状基序是与 AtNSE2 的三个α基序（与 AtMMS21 同源）结合所必需的。通过遗传分析以及分析突变体 nse1 和 nse3 胚胎中细胞命运决定的分子标记物（STM、WOX5 和 WOX8），我们发现 AtNSE1 和 AtNSE3 在早期胚胎发育中起非冗余作用，并且顶端分生组织和下胚轴的分化在突变体中失败，导致生长素运输和响应受损。然而，突变体中的悬浮胚上细胞似乎具有适当的胚胎细胞特性。细胞学检查表明，细胞死亡始于早期胚胎阶段，并且 nse1 和 nse3 突变体胚胎中的液泡程序性细胞死亡和坏死导致胚珠夭折。因此，AtNSE1 和 AtNSE3 对于维持早期胚胎发生过程中的细胞活力和生长是必不可少的。我们的结果提高了对 SMC5/6 复合物在拟南芥早期胚胎发生中的功能的理解。
