Failure of modularity remains a significant challenge for synthetic gene circuits assembled with tested modules as they often do not function as expected. Competition over shared limited gene expression resources is a crucial underlying reason. Here, we first built a synthetic cascading bistable switches (Syn-CBS) circuit in a single strain with two coupled self-activation modules to achieve two successive cell fate transitions. Interestingly, we found that the in vivo transition path was redirected as the activation of one switch always prevailed against the other instead of the theoretically expected coactivation. This qualitatively different type of resource competition between the two modules follows a 'winner-takes-all' rule, where the winner is determined by the relative connection strength between the modules. To decouple the resource competition, we constructed a two-strain circuit, which achieved successive activation and stable coactivation of the two switches. We unveiled a nonlinear resource competition within synthetic gene circuits and provided a division of labor strategy to minimize unfavorable effects.

中文翻译：

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赢家通吃所有资源竞争重新导向级联的细胞命运过渡

对于组装有经过测试的模块的合成基因电路而言，模块化的失败仍然是一项重大挑战，因为它们经常无法按预期运行。共享有限的基因表达资源之间的竞争是根本的根本原因。在这里，我们首先在单个应变中构建了一个合成级联双稳态开关（Syn-CBS）电路，该电路具有两个耦合的自激活模块，以实现两个连续的细胞命运转变。有趣的是，我们发现体内转换路径被重定向，因为一个开关的激活总是比另一个开关占优势，而不是理论上预期的共激活。这两个模块之间的资源竞争在质量上有不同的类型，遵循“赢者通吃”的规则，其中赢家由模块之间的相对连接强度决定。为了消除资源竞争，我们构建了一个两应变电路，该电路实现了两个开关的连续激活和稳定共激活。我们公布了合成基因电路内的非线性资源竞争，并提供了分工策略以最大程度地减少不利影响。