背景回顾：The endosperm is a nutritive tissue supporting embryo growth in flowering plants. Most commonly, the endosperm initially develops as a coenocyte (multinucleate cell) and then cellularizes. This process of cellularization is frequently disrupted in hybrid seeds generated by crosses between different flowering plant species or plants that differ in ploidy, resulting in embryo arrest and seed lethality. 

提出问题：The reason for embryo arrest upon cellularization failure remains unclear. 

结果1-胚乳细胞化与胚胎发育：In this study, we show that triploid Arabidopsis thaliana embryos surrounded by uncellularized endosperm mount an osmotic stress response that is connected to increased levels of abscisic acid (ABA) and enhanced ABA responses. 

结果2-ABA与胚乳细胞化：Impairing ABA biosynthesis and signalling aggravated triploid seed abortion, while increasing endogenous ABA levels as well as the exogenous application of ABA induced endosperm cellularization and suppressed embryo growth arrest. 

结论：Taking these results together, we propose that endosperm cellularization is required to establish dehydration tolerance in the developing embryo, ensuring its survival during seed maturation.

ABA can rescues 3x seeds in an in vitro culture system.

在有花植物中，胚乳是支撑胚胎生长发育的营养组织。多数情况下，胚乳起始于一个多核细胞，然后细胞化。由不同有花植物物种或者不同倍性植物杂交形成的种子，其胚乳的细胞化过程经常会中断，从而导致胚胎发育的终止和种子的死亡。但是，胚乳细胞化失败导致胚胎发育终止的原因还不清楚。本文中，作者发现三倍体拟南芥的胚胎周围是非细胞化的胚乳，且胚胎表现出渗透胁迫响应，该响应与脱落酸ABA含量的增加和ABA响应的增强有关。ABA生物合成和信号转导的缺陷会加强三倍体种子的败育表型，而增加内源的ABA水平以及外施ABA能够诱导胚乳的细胞化，抑制胚胎生长的停滞。综上，作者提出胚乳的细胞化对于正在发育中的胚胎建立脱水耐受性是必须的，以保证其在种子成熟过程中的存活。

** Claudia Köhler **