Identifying receptor-like kinases that enable <i>Caulobacter</i> RHG1 to promote plant growth in <i>Arabidopsis thaliana</i>

Plants express an array of receptor-like kinases (RLKs) to control development and communicate with their environment. Many RLKs are uncharacterized and some of them are expected to regulate plant responses to plant growth-promoting rhizobacteria (PGPR). Despite documented effects induced by <i>Caulobacter</i> RHG1, the underlying signaling pathways and the involved RLKs remain uncharted. Through a targeted RLK mutant screening, we aimed to decipher the receptors that steer the <i>Caulobacter</i> RHG1-induced growth promotion in <i>Arabidopsis thaliana</i>. We identified four RLKs that are pivotal in the RHG1-<i>Arabidopsis</i> interaction, including the coreceptors SOMATIC EMBRYOGENESIS RECEPTOR-LIKE KINASE 1 (SERK1) and BRASSINOSTEROID INSENSITIVE 1-ASSOCIATED KINASE 1 (BAK1/SERK3), which act redundantly in the RHG1-Arabidopsis interaction, possibly by interplaying with the unknown RLK AT3G28040 and the immunity-related ELONGATION FACTOR-TU RECEPTOR (EFR). These results shed new light on the molecular dynamics orchestrating plant responses to PGPR, and concurrently contribute a crucial piece to the intricate puzzle of RLK interactions. <b>Key policy highlights</b>Four RLKs; BAK1, SERK1, EFR, and AT3G28040 (RRHG) are involved in the RHG1-<i>Arabidopsis</i> interaction.BAK1 and SERK1, two well-described co-receptors, act redundantly and play a pivotal role in the RHG1-driven growth promotion, possibly by interplaying with the unknown RLK AT3G28040 and the immunity-related RLK EFR.Most known development – and immunity-related RLKs barely influence RHG1-driven plant growth promotion in <i>Arabidopsis</i>. Four RLKs; BAK1, SERK1, EFR, and AT3G28040 (RRHG) are involved in the RHG1-<i>Arabidopsis</i> interaction. BAK1 and SERK1, two well-described co-receptors, act redundantly and play a pivotal role in the RHG1-driven growth promotion, possibly by interplaying with the unknown RLK AT3G28040 and the immunity-related RLK EFR. Most known development – and immunity-related RLKs barely influence RHG1-driven plant growth promotion in <i>Arabidopsis</i>.植物通过表达一系列类受体激酶（receptor-like kinases, RLKs）以调控自身发育并与外界环境进行信号交流。目前仍有大量RLKs的功能尚未被解析，其中部分有望调控植物对植物促生根际细菌（plant growth-promoting rhizobacteria, PGPR）的应答反应。尽管柄杆菌属（Caulobacter）RHG1菌株诱导的生物学效应已有报道，但其背后的信号通路及参与的RLKs仍未明确。本研究通过靶向RLK突变体筛选，旨在解析介导拟南芥（Arabidopsis thaliana）响应柄杆菌RHG1诱导生长促生作用的受体蛋白。我们鉴定出4种在RHG1-拟南芥互作中发挥关键作用的RLKs，包括共受体体细胞胚胎发生类受体激酶1（SOMATIC EMBRYOGENESIS RECEPTOR-LIKE KINASE 1, SERK1）与油菜素类固醇不敏感1相关激酶1（BRASSINOSTEROID INSENSITIVE 1-ASSOCIATED KINASE 1, BAK1/SERK3），二者在RHG1-拟南芥互作中功能冗余，可能与未知RLK AT3G28040及免疫相关的延伸因子Tu受体（ELONGATION FACTOR-TU RECEPTOR, EFR）协同发挥作用。本研究结果为解析植物响应PGPR的分子动态调控机制提供了新视角，同时也为破解RLK互作的复杂谜题提供了关键线索。 **核心研究亮点** 1. 4种RLKs（BAK1、SERK1、EFR及AT3G28040，又称RRHG）参与RHG1-拟南芥互作过程。 2. 两种已被广泛研究的共受体BAK1与SERK1功能冗余，在RHG1介导的生长促生过程中发挥关键作用，其调控机制可能与未知RLK AT3G28040及免疫相关RLK EFR的协同互作有关。 3. 绝大多数已报道的发育及免疫相关RLKs几乎不对拟南芥中RHG1介导的生长促生效应产生影响。