Summary A unique cell size‐sensing mechanism is at the heart of the life cycle of diatoms. During population growth, cell size decreases until a sexual size threshold (SST) is reached, below which cells become sexually competent. In most pennate diatoms, the two mating types undergo biochemical and behavioral differentiation below the SST, although the molecular pathways underlying their size‐dependent maturation remain unknown. Here, we developed a method to shorten the generation time of Cylindrotheca closterium through single‐cell microsurgery, enabling the transcriptomic comparison of genetically identical large and undifferentiated cells with small, sexually competent cells for six different genotypes. We identified 21 genes upregulated in small cells regardless of their mating type, revealing how cells undergo specific transcriptional reprogramming when passing the SST. Furthermore, we revealed a size‐regulated gene cluster with three mating type‐specific genes susceptible to sex‐inducing pheromones. In addition, comparative transcriptomics confirmed the shared mating type specificity of Mating‐type Related Minus 2 homologs in three pennate diatoms, suggesting them to be part of a conserved partner recognition mechanism. This study sheds light on how diatoms acquire sexual competence in a strictly size‐dependent manner, revealing a complex machinery underlying size‐dependent maturation, mating behavior, and heterothally in pennate diatoms.

中文翻译：

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羽状硅藻中细胞大小感应和交配类型分化的分子指纹


总结 独特的细胞大小感应机制是硅藻生命周期的核心。在种群生长过程中，细胞大小减小，直到达到性大小阈值 （SST），低于该阈值时，细胞具有性能力。在大多数羽状硅藻中，两种交配类型在 SST 以下经历生化和行为分化，尽管其大小依赖性成熟的分子途径仍然未知。在这里，我们开发了一种通过单细胞显微外科手术缩短 Cylindrotheca closterium 生成时间的方法，能够将遗传相同的未分化大细胞与六种不同基因型的小的、具有性感受态的细胞进行转录组学比较。我们鉴定了 21 个在小细胞中上调的基因，无论它们的交配类型如何，揭示了细胞在通过 SST 时如何进行特异性转录重编程。此外，我们揭示了一个大小调节的基因簇，其中包含三个对性诱导信息素敏感的交配类型特异性基因。此外，比较转录组学证实了三个羽状硅藻中交配型相关 Minus 2 同源物的共同交配类型特异性，表明它们是保守伴侣识别机制的一部分。这项研究阐明了硅藻如何以严格依赖于大小的方式获得性能力，揭示了羽状硅藻中大小依赖性成熟、交配行为和异质性的复杂机制。