F-actin associated proteins implicate new mechanisms involved in SI-PCD

自交不亲和性（SI）是显花植物防止自交受精的重要机制，否则会导致不希望的近交和植物适合度的丧失。因此，SI为开花植物的进化成功做出了重大贡献。授粉后，SI利用细胞-细胞识别通过抑制花粉管生长来防止自花受精，这对于将精细胞输送到雌蕊内的卵细胞至关重要。这涉及雌蕊表达的蛋白质和同源花粉蛋白质之间的高度特异性相互作用，其导致识别和抑制遗传上相同或自交（不亲和）的花粉，但不识别和抑制杂交（亲和）的花粉。在虞美人（罂粟）中，雌蕊的柱头分泌一种小蛋白（PrsS），作为信号“配体”。在授粉后，PrsS与表达SI受体（PrpS）的“自我”花粉特异性地相互作用，允许花粉区分“自我”和“非自我”雌性伴侣。这种相互作用是细胞-细胞识别和确定接受或拒绝的关键步骤，其在不相容的花粉中触发复杂的信号网络，并导致花粉被抑制并“被告知”自杀：“程序性细胞死亡”（PCD）JCD对于所有高等生物体中的一系列过程是必不可少的。它对植物的正常发育至关重要，在植物的生命周期中起着决定性的作用，包括受精，胚胎发育和排斥自花花粉。它们都依赖于严格控制和执行的PCD。参与的科学家在我们对植物PCD的理解中发挥了开拓性作用。主要的突破来自于动物PCD机制的关键核心组件与植物中的相似。然而，我们对植物PCD的详细分子调控和下游过程的理解仍然在很大程度上是未知的，并且落后于动物细胞中的PCD。我们最近在罂粟SI的PCD研究中取得了几项突破，这些突破构成了该项目的基础。SI触发肌动蛋白细胞骨架的戏剧性变化，肌动蛋白细胞骨架是一种内部蛋白质结构，有助于细胞的形状，支持和运动。我们最近发现SI导致细胞内容物（胞质溶胶）的急剧酸化。其他最近的发现表明，一种特殊类型的内吞作用，细胞吸收分子的过程。该项目将进行第一个活细胞成像研究，以发现在SI期间肌动蛋白细胞骨架发生了什么。其他研究，使用遗传学，显微镜和生物化学将调查这些不同的过程究竟如何机械控制SI诱导的PCD。这些基础研究很可能会在科学界产生兴奋，因为它们将提供重要的机理见解肌动蛋白在SI-PCD中的作用和[pH]cyt在介导这一作用。确定这些过程中的一些过程之间的联系对于植物细胞来说将是全新的。分析调控SI-PCD的关键分子机制对于我们全面理解PCD的进化保守性具有重要意义。在实践中，了解SI-PCD中涉及的机制可以导致对植物育种有用的应用。生育力和结实率对作物产量和粮食安全至关重要。将SI-PCD性状转移到粮食作物中可能有助于植物育种者开发F1杂交种子，从而更高效、更经济地生产更大、更高产的F1杂交植物。目前，人工去雄是用来生产F1杂交种子，这是费时和昂贵的。将SI-PCD引入作物物种允许其在没有任何去雄的情况下进行杂交，因为没有自花花粉可以使这些植物受精。因此，利用SI-PCD的知识为F1代杂交作物育种提供了一种潜在的替代手段。

Self-incompatibility (SI) is an important mechanism used by flowering plants to prevent self-fertilization, which would otherwise result in undesirable inbreeding and loss of plant fitness. For this reason, SI has made a significant contribution to the evolutionary success of flowering plants. After pollination, SI utilizes cell-cell recognition to prevent self-fertilization by inhibition of pollen tube growth, which is crucial for the delivery of sperm cells to the egg cell inside the pistil. This involves a highly specific interaction between a pistil-expressed protein and a cognate pollen protein that results in recognition and inhibition of genetically identical or self- (incompatible) pollen, but not cross (compatible) pollen. In Papaver rhoeas (field poppy), the stigma of the pistil secretes a small protein (PrsS) which acts as a signalling "ligand". Upon pollination, PrsS interacts specifically with "self" pollen expressing the SI receptor (PrpS), allowing pollen to distinguish between "self" and "non-self" female partners. This interaction is the critical step in cell-cell recognition and determining acceptance or rejection which triggers a complex network of signalling in the incompatible pollen and results in pollen being inhibited and "told" to commit suicide: "Programmed Cell Death" (PCD).PCD is essential for a range of processes in all higher organisms. It is vital for normal plant development, playing a decisive role in the life cycle of plants, including fertilisation, embryo development, and rejection of self-pollen. They all depend on tightly controlled and executed PCD. The scientists involved have played a pioneering role in our understanding of plant PCD. Major breakthroughs have come from establishing that key core components of animal PCD machinery are similar to those in plants. However, our understanding of the detailed molecular regulation and downstream processes of plant PCD are still largely unknown and lag behind that of PCD in animal cells. We have made several recent breakthroughs in our PCD studies in Papaver SI that form the basis of this project. SI triggers dramatic changes of the actin cytoskeleton, an internal protein structure that helps a cell with shape, support, and movement. We recently discovered that SI leads to dramatic acidification of the cell content (cytosol). Other recent findings suggest the involvement of a special type of endocytosis, a process by which cells absorb molecules. This project will carry out the first live-cell imaging studies to discover exactly what happens to the actin cytoskeleton during SI. Other studies, using genetics, microscopy and biochemistry will investigate exactly how these different processes mechanistically control SI-induced PCD. These fundamental studies are likely to generate excitement in the scientific community as they will provide important mechanistic insights into the role of actin in SI-PCD and the role of [pH]cyt in mediating this. Identifying links between some of these processes will be completely novel for plant cells. Analyzing key molecular mechanisms involved in regulating SI-PCD will be important for our general understanding of evolutionary conservation of PCD. On a practical note, understanding the mechanisms involved in SI-PCD can lead to applications useful to plant breeding. Fertility and seed set are critical for crop yield and thus Food Security. The transfer of SI-PCD traits into food crops could potentially help plant breeders develop F1 hybrid seeds, which produce bigger and more productive F1 hybrid plants, more efficiently and economically. Currently, hand-emasculation is used to produce F1 hybrid seeds, which is time-consuming and expensive. Introducing SI-PCD into a crop species allows it to be crossed without any emasculation, as no self-pollen can fertilize these plants. Thus, utilization of knowledge on SI-PCD provides a potential alternative means to breed F1 hybrid crops.