背景回顾：Flowering plants have evolved numerous intraspecific and interspecific prezygotic reproductive barriers to prevent production of unfavourable offspring. Within a species, self-incompatibility (SI) is a widely utilized mechanism that rejects self-pollen to avoid inbreeding depression. Interspecific barriers restrain breeding between species and often follow the SI × self-compatible (SC) rule, that is, interspecific pollen is unilaterally incompatible (UI) on SI pistils but unilaterally compatible (UC) on SC pistils. 

提出问题：The molecular mechanisms underlying SI, UI, SC and UC and their interconnections in the Brassicaceae remain unclear. 

单向杂交不亲和：Here we demonstrate that the SI pollen determinant S-locus cysteine-rich protein/S-locus protein 11 (SCR/SP11) or a signal from UI pollen binds to the SI female determinant S-locus receptor kinase (SRK), recruits FERONIA (FER) and activates FER-mediated reactive oxygen species production in SI stigmas to reject incompatible pollen. 

单向杂交亲和：For compatible responses, diverged pollen coat protein B-class from SC and UC pollen differentially trigger nitric oxide, nitrosate FER to suppress reactive oxygen species in SC stigmas to facilitate pollen growth in an intraspecies-preferential manner, maintaining species integrity. 

结论：Our results show that SRK and FER integrate mechanisms underlying intraspecific and interspecific barriers and offer paths to achieve distant breeding in Brassicaceae crops.

有花植物演化出许多种内和种间的受精前生殖障碍，以防产生不良的子代。在同一物种内，自交不亲和（SI）是一种被广泛运用的机制，通过拒绝来自自身的花粉从而避免近交衰退。种间障碍会阻碍物种之间的繁殖，通常遵守自交不亲和（SI）×自交亲和（SC）准则，即种间的花粉在SI柱头上是单向不亲和（UI），而在SC柱头上是单向亲和（UC）。至今，在十字花科中有关自交不亲和、单向不亲和、自交亲和、单向亲和及其相互之间关联的底层分子机制还不清楚。本文中，作者发现自交不亲和花粉决定因子S位点富含半胱氨酸蛋白/S位点蛋白（SCR/SP11）或来自单向不亲和花粉的一个信号，会结合到自交不亲和雌性决定因子S位点受体激酶（SRK）上，招募FER并激活FER介导的ROS产生，从而使得自交不亲和柱头拒绝不亲和的花粉。对于亲和响应，自交亲和和单向亲和花粉的花粉外被蛋白B类肽PCP-Bs发生分化，差异地诱导NO，从而亚硝基化FER以抑制自交亲和柱头上的ROS，以种内优先的方式促进花粉的生长，最终维持物种的完整性。本文的研究结果揭示SRK和FER整合了种内和种间的杂交障碍机制，为十字花科作物的远缘育种提供了新的途径。

** 段巧红 **