Pérez-Mendoza Daniel, Aragón Isabel M, Prada-Ramírez Harold A, Romero-Jiménez Lorena, Ramos Cayo, Gallegos María-Trinidad, Sanjuán Juan
Dpto. Microbiología del Suelo y Sistemas Simbióticos, Estación Experimental del Zaidín, CSIC, Granada, Spain.
Área de Genética, Universidad de Málaga, Instituto de Hortofruticultura Subtropical y Mediterránea "La Mayora", Universidad de Málaga-CSIC (IHSM-UMA-CSIC), Málaga, Spain.
PLoS One. 2014 Mar 13;9(3):e91645. doi: 10.1371/journal.pone.0091645. eCollection 2014.
Despite a recent burst of research, knowledge on c-di-GMP signaling pathways remains largely fragmentary and molecular mechanisms of regulation and even c-di-GMP targets are yet unknown for most bacteria. Besides genomics or bioinformatics, accompanying alternative approaches are necessary to reveal c-di-GMP regulation in bacteria with complex lifestyles. We have approached this study by artificially altering the c-di-GMP economy of diverse pathogenic and mutualistic plant-interacting bacteria and examining the effects on the interaction with their respective host plants. Phytopathogenic Pseudomonas and symbiotic Rhizobium strains with enhanced levels of intracellular c-di-GMP displayed common free-living responses: reduction of motility, increased production of extracellular polysaccharides and enhanced biofilm formation. Regarding the interaction with the host plants, P. savastanoi pv. savastanoi cells containing high c-di-GMP levels formed larger knots on olive plants which, however, displayed reduced necrosis. In contrast, development of disease symptoms in P. syringae-tomato or P. syringae-bean interactions did not seem significantly affected by high c-di-GMP. On the other hand, increasing c-di-GMP levels in symbiotic R. etli and R. leguminosarum strains favoured the early stages of the interaction since enhanced adhesion to plant roots, but decreased symbiotic efficiency as plant growth and nitrogen contents were reduced. Our results remark the importance of c-di-GMP economy for plant-interacting bacteria and show the usefulness of our approach to reveal particular stages during plant-bacteria associations which are sensitive to changes in c-di-GMP levels.
尽管最近研究激增，但关于环二鸟苷酸（c-di-GMP）信号通路的知识仍然大多支离破碎，对于大多数细菌而言，其调控的分子机制乃至c-di-GMP的靶标仍不为人所知。除了基因组学或生物信息学之外，还需要其他辅助方法来揭示具有复杂生活方式的细菌中的c-di-GMP调控。我们通过人为改变多种与植物相互作用的致病和共生细菌的c-di-GMP水平，并研究其对与各自宿主植物相互作用的影响来开展这项研究。细胞内环二鸟苷酸水平升高的植物致病假单胞菌和共生根瘤菌菌株表现出共同的自由生活反应：运动性降低、胞外多糖产量增加以及生物膜形成增强。关于与宿主植物的相互作用，含有高c-di-GMP水平的丁香假单胞菌番茄致病变种（P. savastanoi pv. savastanoi）细胞在橄榄植株上形成更大的瘤，但坏死程度降低。相比之下，丁香假单胞菌与番茄或丁香假单胞菌与菜豆相互作用中疾病症状的发展似乎不受高c-di-GMP的显著影响。另一方面，共生的埃氏根瘤菌（R. etli）和豌豆根瘤菌（R. leguminosarum）菌株中c-di-GMP水平的升高有利于相互作用的早期阶段，因为对植物根的附着力增强，但由于植物生长和氮含量降低，共生效率下降。我们的结果表明c-di-GMP水平对与植物相互作用的细菌很重要，并表明我们的方法对于揭示植物-细菌关联中对c-di-GMP水平变化敏感的特定阶段很有用。
