Valente Rita S, Nadal-Jimenez Pol, Carvalho André F P, Vieira Filipe J D, Xavier Karina B
Instituto Gulbenkian de Ciência, Oeiras, Portugal.
Instituto Gulbenkian de Ciência, Oeiras, Portugal
mBio. 2017 May 23;8(3):e00398-17. doi: 10.1128/mBio.00398-17.
Bacterial communities can sense their neighbors, regulating group behaviors in response to cell density and environmental changes. The diversity of signaling networks in a single species has been postulated to allow custom responses to different stimuli; however, little is known about how multiple signals are integrated and the implications of this integration in different ecological contexts. In the plant pathogen (formerly ), two signaling networks-the N-acyl homoserine lactone (AHL) quorum-sensing system and the Gac/Rsm signal transduction pathway-control the expression of secreted plant cell wall-degrading enzymes, its major virulence determinants. We show that the AHL system controls the Gac/Rsm system by affecting the expression of the regulatory RNA RsmB. This regulation is mediated by ExpR2, the quorum-sensing receptor that responds to the cognate AHL but also to AHLs produced by other bacterial species. As a consequence, this level of regulation allows to bypass the Gac-dependent regulation of RsmB in the presence of exogenous AHLs or AHL-producing bacteria. We provide evidence that this pivotal role of RsmB in signal transduction is important for the ability of to induce virulence in response to other AHL-producing bacteria in multispecies plant lesions. Our results suggest that the signaling architecture in was coopted to prime the bacteria to eavesdrop on other bacteria and quickly join the efforts of other species, which are already exploiting host resources. Quorum-sensing mechanisms enable bacteria to communicate through small signal molecules and coordinate group behaviors. Often, bacteria have various quorum-sensing receptors and integrate information with other signal transduction pathways, presumably allowing them to respond to different ecological contexts. The plant pathogen has two N-acyl homoserine lactone receptors with apparently the same regulatory functions. Our work revealed that the receptor with the broadest signal specificity is also responsible for establishing the link between the main signaling pathways regulating virulence in This link is essential to provide with the ability to induce virulence earlier in response to higher densities of other bacterial species. We further present evidence that this novel regulatory link enables to join related bacteria in the effort to degrade host tissue in multispecies plant lesions. Our work provides support for the hypothesis that interspecies interactions are among the major factors influencing the network architectures observed in bacterial quorum-sensing pathways.
细菌群落能够感知其邻居，根据细胞密度和环境变化调节群体行为。据推测，单一物种中信号网络的多样性可使其对不同刺激做出定制反应；然而，对于多种信号如何整合以及这种整合在不同生态环境中的意义，我们却知之甚少。在植物病原菌（以前称为）中，两个信号网络——N-酰基高丝氨酸内酯（AHL）群体感应系统和Gac/Rsm信号转导途径——控制着分泌型植物细胞壁降解酶的表达，而这些酶是其主要的毒力决定因素。我们发现，AHL系统通过影响调控RNA RsmB的表达来控制Gac/Rsm系统。这种调控由ExpR2介导，ExpR2是群体感应受体，它既能响应同源AHL，也能响应其他细菌物种产生的AHL。因此，在存在外源AHL或产生AHL的细菌时，这种调控水平使能够绕过RsmB的Gac依赖性调控。我们提供的证据表明，RsmB在信号转导中的这一关键作用对于在多物种植物病斑中响应其他产生AHL的细菌诱导毒力的能力至关重要。我们的结果表明，中的信号架构被用来使细菌能够窃听其他细菌，并迅速加入其他已经在利用宿主资源的物种的行动中。群体感应机制使细菌能够通过小信号分子进行交流并协调群体行为。通常，细菌有各种群体感应受体，并将信息与其他信号转导途径整合，这可能使它们能够对不同的生态环境做出反应。植物病原菌有两个N-酰基高丝氨酸内酯受体，其调控功能明显相同。我们的工作表明，信号特异性最广的受体也负责在中建立调控毒力的主要信号途径之间的联系。这种联系对于使能够在更高密度的其他细菌物种存在时更早地诱导毒力至关重要。我们进一步提供的证据表明，这种新的调控联系使能够在多物种植物病斑中与相关细菌一起努力降解宿主组织。我们的工作支持了这样一种假设，即种间相互作用是影响细菌群体感应途径中观察到的网络架构的主要因素之一。
