Under conditions in which budding yeast form colonies and then undergo meiosis/sporulation, the resulting colonies are organized such that a sharply defined layer of meiotic cells overlays a layer of unsporulated cells termed "feeder cells." This differentiation pattern requires activation of both the Rlm1/cell-wall integrity pathway and the Rim101/alkaline-response pathway. In the current study, we analyzed the connection between these two signaling pathways in regulating colony development by determining expression patterns and cell-autonomy relationships. We present evidence that two parallel cell-nonautonomous positive-feedback loops are active in colony patterning, an Rlm1-Slt2 loop active in feeder cells and an Rim101-Ime1 loop active in meiotic cells. The Rlm1-Slt2 loop is expressed first and subsequently activates the Rim101-Ime1 loop through a cell-nonautonomous mechanism. Once activated, each feedback loop activates the cell fate specific to its colony region. At the same time, cell-autonomous mechanisms inhibit ectopic fates within these regions. In addition, once the second loop is active, it represses the first loop through a cell-nonautonomous mechanism. Linked cell-nonautonomous positive-feedback loops, by amplifying small differences in microenvironments, may be a general mechanism for pattern formation in yeast and other organisms.

中文翻译：

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边界如何形成：链接的非自主反馈环路调节酵母菌落中的模式形成。

在芽殖酵母形成菌落然后经历减数分裂/孢子形成的条件下，所得菌落被组织成使得减数分裂细胞的清晰界定层覆盖被称为“饲养细胞”的未孢子细胞层。这种分化模式需要激活 Rlm1/细胞壁完整性途径和 Rim101/碱性反应途径。在当前的研究中，我们通过确定表达模式和细胞自主关系来分析这两种信号通路在调节集落发育中的联系。我们提供的证据表明，两个平行的细胞非自主正反馈环在集落模式中活跃，一个Rlm1-Slt2环在饲养细胞中活跃，一个Rim101-Ime1环在减数分裂细胞中活跃。Rlm1-Slt2 环首先表达，随后通过细胞非自主机制激活 Rim101-Ime1 环。一旦激活，每个反馈环路都会激活特定于其集落区域的细胞命运。与此同时，细胞自主机制抑制这些区域内的异位命运。此外，一旦第二个循环处于活动状态，它就会通过细胞非自主机制抑制第一个循环。通过放大微环境中的微小差异，连接的细胞非自主正反馈回路可能是酵母和其他生物体中模式形成的一般机制。