Control of Entry into the Female Germline in Maize

真核生物的主要发育阶段之一是减数分裂。由于其深远的影响，即染色体组减少一半，再加上重组和染色体组的新组装，决定何时以及哪些细胞进行减数分裂是严格控制的。与动物在胚胎发生早期通过特定的细胞谱系（生殖系）形成减数细胞不同，开花植物在发育后期对生殖器官中的体细胞进行重新编程，产生一个原始孢子细胞，由此衍生出减数细胞，并由此启动一个生殖系，导致配子的产生。我们对植物，特别是农作物的种系起始知之甚少，而且从动物和酵母中发现的减数分裂进入的调节因子在植物中都不保守。在玉米、水稻和拟南芥中已经发现了一些基因，这些基因在孢子母细胞和减数细胞的形成中起作用。然而，相应的研究也表明，开花植物的种系起始机制可能是多样化的。然而，一个新兴的原理似乎是，生殖系的建立需要干细胞样细胞的形成，例如，在拟南芥中，干细胞因子WUSCHEL的功能对于这一过程的必要性。在这里，我们将研究最终导致玉米雌性减数细胞形成的细胞规范事件。在与该研究单位的其他成员密切合作中，我们将解决多能干细胞样细胞如何被重新编程以进入女性生殖系的问题。为了达到这一目标，我们将首先通过应用最近建立的活细胞成像方法来生成种系进入的细胞学框架。这项工作将辅以年轻胚珠细胞的单细胞测序，以跟踪其在种系建立过程中的发育轨迹。最后，我们将通过特定的功能获得和功能丧失方法挑战种系分化。与其他联盟成员一起，我们将对作物发育过程中干细胞样细胞的起始、维持和终止形成一个综合的观点。

One of the major developmental phase transitions in eukaryotes is meiosis. Due to its far-reaching consequences, i.e. reduction of the chromosome set by half coupled to recombination and the new assembly of chromosome sets, the decision when and which cells undergo meiosis is tightly controlled. In contrast to animals that specific a cell lineage (germline) leading to the formation of meiocytes early during embryogenesis, flowering plants reprogram somatic cells in reproductive organs late in development to produce an archesporial cell from which a meiocyte is derived and with that initiate a germline that leads to the production of gametes. Very little is known about germline initiation in plants, especially in crops, and none of the regulators of meiotic entry known from animals and yeast are conserved in plants. A few genes have been identified in maize, rice, and mostly Arabidopsis that play a role in the specification of archesporial cells and meiocytes. However, the corresponding studies also show that the mechanisms of germline initiation are likely diversified in flowering plants. An emerging principle, however, appears to be that the setup of the germline requires the formation of stem cell-like cells as for instance seen by the necessity of the function of the stem cell factor WUSCHEL for this process in Arabidopsis. Here, we will study the cellular specification events that ultimately lead to the formation of female meiocytes in the crop species maize. In close collaboration with the other members of this research unit, we will address the question how pluripotent stem cell-like cells are reprogramed to enter the female germline. To reach this goal, we will first generate a cytological framework of germline entry by applying a recently established live cell imaging approach. This work will be complemented by single cell sequencing of young ovule cells to follow their developmental trajectories during germline establishment. Finally, we will challenge germline differentiation by specific gain-of-function and loss-of-function approaches. Together with the other consortium members we will then develop an integrated view on the initiation, maintenance and termination of stem cell-like cells during crop development.