Domínguez-Cerván Hilario, Barrientos-Moreno Laura, Díaz-Martínez Luis, Murillo Jesús, Pérez-Dorado Inmaculada, Ramos Cayo, Rodríguez-Moreno Luis
Área de Genética, Facultad de Ciencias, Universidad de Málaga, Campus Teatinos, Málaga, Spain.
Instituto de Hortofruticultura Subtropical y Mediterránea "La Mayora", Consejo Superior de Investigaciones Científicas (IHSM-UMA-CSIC), Málaga, Spain.
PLoS Pathog. 2025 Aug 1;21(8):e1013121. doi: 10.1371/journal.ppat.1013121. eCollection 2025 Aug.
Phytopathogenic bacteria secrete diverse virulence factors to manipulate host defenses and establish infection. Characterization of the type III secretion system (T3SS)- and HrpL-independent secretome (T3-IS) in Pseudomonas savastanoi pv. savastanoi (Psv), the causal agent of olive knot disease, identified five secreted LysM-containing proteins (LysM1-LysM5) associated with distinct physiological processes critical for infection. Functional predictions from network analyses suggest that LysM1, LysM2, and LysM4 may participate in type IV pilus-related functions, while LysM3 and LysM5 are likely to possess peptidoglycan hydrolase domains critical for cell division. Supporting these predictions, loss of LysM1 function resulted in impaired twitching and swimming motility, highlighting a role in pilus-mediated movement and early host colonization. In contrast, mutants lacking LysM3 or LysM5 exhibited pronounced filamentation and defective bacterial division, underscoring their essential role in septation, a process crucial for both in planta fitness and tumor formation. Structural modeling and protein stability assays demonstrate that LysM3 interacts with peptidoglycan fragments such as tetra-N-acetylglucosamine and meso-diaminopimelic acid, as well as with zinc ions, through conserved LysM and M23 domains. LysM3 also displayed selective bacteriostatic activity against co-inhabiting Gram-negative bacterial competitors, such as Pantoea agglomerans and Erwinia toletana. Our findings highlight the relevance of LysM proteins in maintaining bacterial integrity, motility, and competitive fitness, which are crucial for successful host infection. This study expands the functional repertoire of LysM-containing proteins and reveals their broader impact on bacterial virulence and adaptation to the plant-associated niche.
植物病原细菌分泌多种毒力因子来操纵宿主防御并建立感染。对引起橄榄结瘤病的野油菜黄单胞菌野油菜致病变种（Psv）中III型分泌系统（T3SS）和HrpL非依赖性分泌组（T3-IS）的表征，鉴定出五种分泌的含赖氨酸基序（LysM）蛋白（LysM1-LysM5），它们与感染所需的不同生理过程相关。网络分析的功能预测表明，LysM1、LysM2和LysM4可能参与IV型菌毛相关功能，而LysM3和LysM5可能具有对细胞分裂至关重要的肽聚糖水解酶结构域。支持这些预测的是，LysM1功能丧失导致颤动和游动运动受损，突出了其在菌毛介导的运动和早期宿主定殖中的作用。相比之下，缺乏LysM3或LysM5的突变体表现出明显的丝状化和有缺陷的细菌分裂，强调了它们在隔膜形成中的重要作用，隔膜形成过程对植物体内适应性和肿瘤形成都至关重要。结构建模和蛋白质稳定性分析表明，LysM3通过保守的LysM和M23结构域与肽聚糖片段如四-N-乙酰葡糖胺和内消旋二氨基庚二酸以及锌离子相互作用。LysM3还对共同栖息的革兰氏阴性细菌竞争者，如成团泛菌和托莱塔欧文氏菌，表现出选择性抑菌活性。我们的研究结果突出了LysM蛋白在维持细菌完整性、运动性和竞争适应性方面的相关性，这些对于成功感染宿主至关重要。这项研究扩展了含LysM蛋白的功能库，并揭示了它们对细菌毒力和适应植物相关生态位的更广泛影响。
