Genetic Evidence for Signal Transduction within the Bacillus subtilis GerA Germinant Receptor
Genetic Evidence for Signal Transduction within the Bacillus subtilis GerA Germinant Receptor
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DOI：
10.1128/jb.00470-21
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发表时间：
2022-02-01
影响因子：
3.2
通讯作者：
Rudner, David Z.
中科院分区：
文献类型：
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作者：
Amon, Jeremy D.;Artzi, Lior;Rudner, David Z.
细菌孢子可以通过萌发过程迅速脱离休眠。这一过程开始于孢子膜上的营养受体的激活。枯草芽孢杆菌中的原型萌发剂受体对L-丙氨酸产生反应，并且被认为是由gerA操纵子中的基因gerAA、gerAB和gerAC编码的蛋白质的复合物。GerAB亚基最近已被证明是营养传感器，但除了有助于复合物的稳定性，没有其他功能已归因于其他两个亚基。在这里，我们调查GerAA的作用。我们复活了一个先前表征的等位基因gerA（称为gerA*），携带突变gerAA，并表明它组成激活发芽，即使在存在的野生型拷贝gerA。使用富集策略来筛选gerA* 的抑制因子，我们确定了所有三个gerA基因中恢复功能受体的突变。两种不同gerAB抑制子的表征揭示，一种（gerAB[E105 K]）降低GerA复合物响应L-丙氨酸的能力，而另一种（gerAB（F259 S]）破坏L-丙氨酸识别下游的萌发信号。这些数据反对GerAA直接或间接参与萌发感测的模型。相反，我们的数据表明，GerAA负责转导GerAB感知的营养信号。虽然gerAA的下游步骤尚未被发现，这些结果验证了使用显性负遗传方法阐明gerA信号转导pathway.IMPORTANCE内生孢子形成者是一个广泛的细菌群体，可以进入休眠后饥饿和退出休眠后，感应返回的营养物质。人们对休眠孢子如何感知这些营养物质并做出反应知之甚少。在这里，我们确定了信号转导途径中的一个关键步骤，即孢子检测到氨基酸L-丙氨酸后激活。我们提出了一个模型，提供了一个更完整的图片，这是关键的过程，让休眠孢子发芽和恢复生长。
Bacterial spores can rapidly exit dormancy through the process of germination. This process begins with the activation of nutrient receptors embedded in the spore membrane. The prototypical germinant receptor in Bacillus subtilis responds to L-alanine and is thought to be a complex of proteins encoded by the genes in the gerA operon: gerAA, gerAB, and gerAC. The GerAB subunit has recently been shown to function as the nutrient sensor, but beyond contributing to complex stability, no additional functions have been attributed to the other two subunits. Here, we investigate the role of GerAA. We resurrect a previously characterized allele of gerA (termed gerA*) that carries a mutation in gerAA and show that it constitutively activates germination even in the presence of a wild-type copy of gerA. Using an enrichment strategy to screen for suppressors of gerA*, we identified mutations in all three gerA genes that restore a functional receptor. Characterization of two distinct gerAB suppressors revealed that one (gerAB[E105K]) reduces the GerA complex's ability to respond to L-alanine, while another (gerAB(F259S]) disrupts the germinant signal downstream of L-alanine recognition. These data argue against models in which GerAA is directly or indirectly involved in germinant sensing. Rather, our data suggest that GerAA is responsible for transducing the nutrient signal sensed by GerAB. While the steps downstream of gerAA have yet to be uncovered, these results validate the use of a dominant-negative genetic approach in elucidating the gerA signal transduction pathway.IMPORTANCE Endospore formers are a broad group of bacteria that can enter dormancy upon starvation and exit dormancy upon sensing the return of nutrients. How dormant spores sense and respond to these nutrients is poorly understood. Here, we identify a key step in the signal transduction pathway that is activated after spores detect the amino acid L-alanine. We present a model that provides a more complete picture of this process that is critical for allowing dormant spores to germinate and resume growth.