In multicellular organisms, sexual reproduction requires the separation of the germline from the soma. In flowering plants, the first cells of the germline, so-called spore mother cells (SMCs), differentiate as the reproductive organs form. Here, we explored how organ growth influences and contributes to SMC differentiation. We generated a collection of 92 annotated 3D images capturing ovule primordium ontogeny at cellular resolution in Arabidopsis. We identified a spatio-temporal pattern of cell divisions that acts in a domain-specific manner as the primordium forms, which is coupled with the emergence of a single SMC. Using tissue growth models, we uncovered plausible morphogenetic principles involving a spatially confined growth signal, differential mechanical properties, and cell growth anisotropy. Our analysis also reveals that SMC characteristics first arise in more than one cell but SMC fate becomes progressively restricted to a single cell during organ growth. Altered primordium geometry coincided with a delay in this fate restriction process in katanin mutants. Altogether, our study suggests that tissue geometry canalizes and modulates reproductive cell fate in the Arabidopsis ovule primordium.

中文翻译：

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器官的几何结构引导拟南芥胚珠原基中的细胞命运

在多细胞生物中，有性生殖需要生殖细胞与体细胞分离。在开花植物中，种系的第一批细胞，即所谓的孢子母细胞（SMCs），随着生殖器官的形成而分化。在这里，我们探讨了器官生长如何影响和促进SMC分化。我们在拟南芥中以细胞分辨率生成了92个带注释的3D图像的集合，这些图像捕获了胚珠原基个体发育。我们确定了一种细胞分裂的时空模式，该模式以特定域的方式作为原基形式起作用，并伴随着单个SMC的出现。使用组织生长模型，我们发现了合理的形态发生原理，涉及空间受限的生长信号，不同的机械性能和细胞生长各向异性。我们的分析还显示，SMC特性首先出现在多个细胞中，但在器官生长过程中，SMC的命运逐渐局限于单个细胞。改变了原基的几何形状，同时延迟了katanin突变体的这种命运限制过程。总而言之，我们的研究表明组织的几何形状能够调节和调节拟南芥胚珠原基中的生殖细胞命运。