Evolution of Sexual Reproduction in Plants

近五年来的研究为拟南芥配子生理学和受精机制提供了大量新的见解。这一进展确立了配子是具有高度特异性转录谱的高度分化细胞类型的观点。基于荧光报告和活细胞成像的显微镜技术的进步也改变了研究能力，并提供了有关配子传递、相互作用和染色质重编程的机制的见解。然而，我们对开花植物双重受精的复杂性的理解还远远不够。重要的是，我们对双受精之前的机制起源缺乏任何知识。在此，我们建议使用代表植物进化关键阶段的新兴模型来深入了解配子分化和受精的祖先机制。我们将通过生成地茅、苔藓小壶藓和现存基生开花植物Amborella的表达图谱，建立基因协同功能网络。这些将与拟南芥和重要作物玉米、番茄和水稻的协同功能网络相辅相成。绿藻衣藻将作为外群。这些网络将用于研究开花植物雌雄配子体发育、花粉管生长和受精机制的基因协同功能网络的保护。此外，这些研究将提供新的作物肥力分子标记。例如，我们的目标是确定在单子房（禾本科）和双子房的进化过程中从古代被子植物中丢失的受精因子，以及在被子植物谱系中重新进化的受精因子。我们还将直接测试雄性配子发育所需的既定调节因子的功能，以及从我们的网络分析中新发现的调节因子，以评估这些调节网络的进化保护程度。预期的研究结果将有助于确定作物有性繁殖过程中环境胁迫所针对的具体机制，并将有助于选择抗胁迫品种。最后，染色质修饰的重编程是动物有性生殖的一个既定特征。该项目产生的数据将提供第一张关于植物配子和受精产物中染色质重编程发生的综合图谱。更好地了解表观遗传重编程事件对于理解生物和非生物胁迫下表观遗传标记的跨代遗传至关重要，因此是提高环境变化下作物生产力的重要组成部分。总而言之，EVOREPRO项目的产出将使人们更深入地了解经济上重要的植物物种有性繁殖的演变。

Research during the past five years has delivered tremendous new insights into gamete physiology and the mechanisms involved in fertilization in Arabidopsis. This progress has established the view that gametes are hyper-differentiated cell types with highly specific transcriptional profiles. Advances in microscopy based on fluorescent reporters and live cell imaging have also transformed research capability and provided insights into the mechanisms involved in gamete delivery, interaction and the reprogramming of chromatin. Yet, our understanding of the complexity of double fertilization that characterises flowering plants is far from complete.Importantly, we lack any knowledge on the origin of mechanisms that predate double fertilization. Here, we propose to use emerging models, representing key stages in plant evolution, to provide insight into the ancestral mechanisms of gamete differentiation and fertilization. We will establish gene co-function networks by generating expression atlases for the liverwort Marchantia, the moss Physcomitrella and the extant basal flowering plant Amborella. These will be complemented with co-function networks from Arabidopsis and the important crops maize, tomato and rice. The green alga Chlamydomonas will serve as an outgroup. These networks will be used to study the conservation of gene co-function networks governing male and female gametogenesis, pollen tube growth and fertilization mechanisms in flowering plants. Moreover, these investigations will provide novel molecular markers of fertility in crops. We aim to identify, for example, fertilization factors which were lost from ancient angiosperms during the evolution of monocots (grasses) and eudicots and those which have evolved de novo in the angiosperm lineage. We will also directly test the function of established regulators required for male gamete development, as well as those newly identified from our network analyses, to assess the extent of evolutionary conservation of these regulatory networks. The expected findings will allow the identification of specific mechanisms that are targeted by environmental stresses during sexual reproduction in crops and will assist in the selection of stress-resistant cultivars. Finally, the reprogramming of chromatin modifications is an established feature of sexual reproduction in animals. Data generated in this project will provide the first comprehensive map of the occurrence of chromatin reprogramming in plant gametes and fertilization products. A better understanding of the epigenetic reprogramming events is pivotal for understanding transgenerational inheritance of epigenetic marks following exposure to biotic and abiotic stress and thus is an essential component for the improvement of crop productivity under environmental changes.In summary, the outputs of the EVOREPRO project will provide a deeper understanding of the evolution of sexual reproduction of economically important plant species.