Cellular signalling mechanisms during pollen-pistil interactions in Brassicaceae

植物通过适当选择遗传多样性的配偶来保持产量、活力和遗传多样性，同时拒绝亲缘关系的伴侣。在大多数开花植物中，成功的繁殖是在授粉的最早阶段控制的，当时花粉与雌性的柱头乳突细胞相互作用。随着花粉和柱头之间良好的(相容的)相互作用，花粉管通过花柱生长并使胚珠受精。相反，为了避免遗传上相似的配偶(自交花粉)，植物利用自交不亲和(SI)系统作为遗传屏障，阻止自交花粉在柱头上发育，只允许杂交花粉发育，从而促进杂交活力和多样性。在油菜的SI反应过程中，花粉(雄)配体SCR/SP11和柱头(雌)SRK(受体激酶)之间的相互作用导致Arc1 E3连接酶被募集到蛋白酶体，其中Arc1促进了各种下游亲和因子的降解。我们已经确定了至少三个下游靶标及其在授粉中的作用。我的长期目标是彻底了解植物繁殖过程中调节亲和性和不亲和性授粉事件的信号机制。描述了三个具体的研究目标。1)我们的初步证据表明，MAPK(丝裂原激活蛋白激酶)在柱头中被结构性地激活，是介导亲和授粉所必需的。我们建议确定参与调节亲和授粉的MAPK的上游调控因子。鉴定这些MAPK的激活子(S)将有助于我们建立亲和的信号通路2)阐明授粉过程中Exo70A1激活的信号机制。将评估MAPKs通过磷酸化影响Exo70A1功能的作用。这一目标将导致完成MAPKs下游亲和相互作用所需的途径3)将JDP1(J结构域蛋白)表征为SI的正调控因子。虽然已经鉴定出了一些ARC1的靶点，但在ARC1之后，还没有发现其他SI途径的正调控因子。JDP1可与Arc1相互作用，抑制JDP1可导致SI的破坏，提示JDP1是SI的正向调节因子。我们建议使用转基因、分子和生化方法来阐明JDP1如何参与SI信号转导。鉴于我们大多数主食的作物产量影响到成功的繁殖，了解驱动作物繁殖潜力的遗传网络对于我们走向全球可持续发展至关重要。我们的研究计划旨在从发现和应用的角度来解决这个问题。通过该计划培训的HQP将拥有在油菜籽行业找到工作的独特优势，并将在学术界、行业和政府获得机会。

Plants maintain their yield, vigour and genetic diversity through appropriate selection of genetically diverse mates while rejecting related partners. In most flowering plants, successful reproduction is controlled at the earliest stages of pollination when the pollen interacts with the stigmatic papillary cell of the female. Following a favourable (compatible) interaction between the pollen and the stigma, the pollen tube grows through the style and fertilizes the ovule. In contrast, to avoid genetically similar mates (self-pollen), plants utilize self-incompatibility (SI) system as a genetic barrier to prevent self-pollen from developing on the stigma, allowing development of only cross-pollen, thereby promoting hybrid vigour and diversity. During SI response in Brassica, interaction between the pollen (male) ligand SCR/SP11 and the stigma (female) SRK (receptor kinase), leads to recruitment of ARC1 E3 ligase to the proteasome, where ARC1 facilitates degradation of various downstream compatibility factors. We have characterized at least three of these downstream targets and their role in pollination. My long-term goal is to gain a thorough understanding of the signaling mechanisms that regulate compatible and incompatible pollination events during plant reproduction. Three specific research objectives are described. 1) Our preliminary evidence suggests that MAPKs (mitogen-activate protein kinases) are constitutively activated in the stigmas and are required for mediating compatible pollination. We propose to identify the upstream regulators of MAPKs that are involved in mediating compatible pollination. Identification of the activator(s) of these MAPKs would allow us to build the compatible signaling pathway 2) Elucidate the signaling mechanism behind activation of Exo70A1 during pollination. The role of MAPKs in influencing the function of Exo70A1 through phosphorylation will be assessed. This objective will lead to completion of the pathway downstream of MAPKs that is required for compatible interactions 3) Characterizing JDP1 (J-domain protein) as a positive regulator of SI. Although a number of targets of ARC1 have been identified, no other positive regulator of SI pathway has been identified after ARC1. JDP1 can interact with ARC1 and suppression of JDP1 leads to breakdown of SI, suggesting JDP1 is a positive regulator of SI. We propose to use transgenic, molecular and biochemical approaches to elucidate how JDP1 participates in SI signaling. Given that crop-yield in most of our staple foods impinge on successful reproduction, understanding the genetic networks that drive the reproductive potential of a crop plant is crucial for our global move toward sustainability. Our research program aims to address this from both a discovery and an applied perspective. The HQPs trained through this program will have a unique advantage of finding jobs in the canola industry and will have opportunities in academia, industry and the government.