Cellular regulation of pollen compatibility and fertility in the Brassicaceae

在芸苔科（芥菜科）中，当花粉粒（雄性）沉积在雌蕊（雌性）顶部时，植物的有性生殖就开始了。相容的花粉粒被雌蕊识别并提供资源，使花粉粒萌发并产生花粉管，为精子细胞提供受精。这些花粉与雌蕊的相互作用受到严格的调控，在受精启动种子生产时至关重要。戈林研究小组研究了这些相互作用的第一阶段：当花粉与雌蕊顶部的柱头乳头细胞接触时。这些乳突可以区分不同的花粉，接受、拒绝或忽略花粉粒。相容花粉被接受，因为它被认为是密切相关的。相比之下，自花粉在许多物种中被拒绝，因为这种自我识别系统用于防止近亲繁殖（自交不亲和）。最后，被忽视的花粉只是因为与花粉的亲缘关系太遥远而无法被识别。因此，这些初始的相互作用仔细地调节和保存了雌雌蕊和雄花粉之间的资源共享，以确保成功受精。为了这项拨款提案，戈林研究小组将研究调节初始花粉-柱头乳头相互作用的细胞-细胞通信事件，并研究这些过程如何在不同的芸苔科物种中保存。具体而言，本研究提出了三个目标：(1)鉴定和表征柱头乳突（雌蕊）中负责识别和响应相容花粉的信号蛋白（如受体）。柱头乳突识别相容花粉的机制目前尚不清楚。(2)探讨基部亲和花粉响应通路中调控分泌的机制。这是柱头乳突中的细胞系统，被认为负责分配资源给相容的花粉粒。(3)明确自噬在花粉自交不亲和排斥中的作用和机制。这是柱头乳突的细胞反应，被认为在拒绝自交花粉以防止近亲繁殖中起重要作用。通过这三个目标，本研究有望对芸苔科植物授粉后早期过程的调控机制有重大的新发现。最终，成功的相容花粉接受对受精和种子产生积极影响，而自不相容的花粉拒绝会阻碍近亲交配产生更健康的后代。因此，本研究对制定提高油菜等十字花科油料作物种子产量的新策略具有重要意义。

In the Brassicaceae (mustard family), sexual plant reproduction is initiated when pollen grains (male) are deposited on top of the pistil (female). Compatible pollen grains are recognized by the pistil and provided resources so that the pollen grains can germinate and produce pollen tubes to deliver sperm cells for fertilization. These pollen-pistil interactions are tightly-regulated and critical as fertilization initiates seed production. The Goring research group examines the first stage of these interactions: when the pollen comes in contact with stigmatic papillar cells at the top of pistil. These papillae can differentiate between different pollen to accept, reject or ignore the pollen grains. Compatible pollen is accepted as it is recognized as being closely-related. In contrast, self'-pollen is rejected in many species as this self-recognition system is used to prevent inbreeding (self-incompatibility). Finally, pollen that is ignored is simply too distantly-related to be recognized. Thus, these initial interactions carefully regulate and conserve the sharing of resources from the female pistil to the male pollen for successful fertilization.For this grant proposal, the Goring research group will investigate the cell-cell communication events that regulate the initial pollen-stigmatic papillae interactions and examine how these processes are conserved in different Brassicaceae species. Specifically, three objectives are proposed for this research:(1) Identify and characterize the signaling proteins in the stigmatic papillae (pistil) that are responsible for recognizing and responding to compatible pollen (e.g. receptors). The mechanism by which stigmatic papillae recognize compatible pollen is currently unknown.(2) Investigate the mechanism of regulated secretion in the basal compatible pollen response pathway. This is the cellular system in the stigmatic papillae that is hypothesized to be responsible for allocating resources to the compatible pollen grains.(3) Define the role and mechanism of autophagy in self-incompatible pollen rejection. This is a cellular response in the stigmatic papillae that is hypothesized to play an important role in rejecting self'-pollen to prevent inbreeding. Through these three objectives, the proposed research is expected to lead to significant new discoveries on the mechanisms regulating early post-pollination processes in the Brassicaceae. Ultimately, successful compatible pollen acceptance has a positive impact on fertilization and seed production, and self-incompatible pollen rejection prevents inbreeding to produce healthier offspring. Hence, this research has important implications for developing new strategies to improve seed productivity in Brassicaceae oilseed crops such as canola.