Lavado-Benito Carla, Murillo Jesús, Martínez-Gil Marta, Ramos Cayo, Rodríguez-Moreno Luis
Área de Genética, Facultad de Ciencias, Universidad de Málaga, Málaga, Spain.
Instituto de Hortofruticultura Subtropical y Mediterránea "La Mayora", Consejo Superior de Investigaciones Científicas (IHSM-UMA-CSIC), Málaga, Spain.
Front Plant Sci. 2024 Feb 5;15:1347982. doi: 10.3389/fpls.2024.1347982. eCollection 2024.
GacS/GacA is a widely distributed two-component system playing an essential role as a key global regulator, although its characterization in phytopathogenic bacteria has been deeply biased, being intensively studied in pathogens of herbaceous plants but barely investigated in pathogens of woody hosts. pv. savastanoi (Psv) is characterized by inducing tumours in the stem and branches of olive trees. In this work, the model strain Psv NCPPB 3335 and a mutant derivative with a complete deletion of gene were subjected to RNA-Seq analyses in a minimum medium and a medium mimicking in planta conditions, accompanied by RT-qPCR analyses of selected genes and phenotypic assays. These experiments indicated that GacA participates in the regulation of at least 2152 genes in strain NCPPB 3335, representing 37.9 % of the annotated CDSs. GacA also controls the expression of diverse genes, and modulates diverse phenotypes, including motility and resistance to oxidative stresses. As occurs with other pathovars of herbaceous plants, GacA regulates the expression of the type III secretion system and cognate effectors. In addition, GacA also regulates the expression of WHOP genes, specifically encoded in strains isolated from woody hosts, and genes for the biosynthesis of phytohormones. A mutant of NCPPB 3335 showed increased virulence, producing large immature tumours with high bacterial populations, but showed a significantly reduced competitiveness in planta. Our results further extend the role of the global regulator GacA in the virulence and fitness of a pathogen of woody hosts.
GacS/GacA是一种广泛分布的双组分系统，作为关键的全局调节因子发挥着重要作用，尽管其在植物致病细菌中的特性研究存在严重偏差，在草本植物病原体中得到了深入研究，但在木本宿主病原体中却鲜有研究。丁香假单胞菌橄榄致病变种（Psv）的特征是在橄榄树的茎和枝上诱发肿瘤。在这项研究中，对模式菌株Psv NCPPB 3335和一个基因完全缺失的突变衍生物在基本培养基和模拟植物体内条件的培养基中进行了RNA测序分析，并对选定基因进行了RT-qPCR分析和表型分析。这些实验表明，GacA参与调控NCPPB 3335菌株中至少2152个基因，占注释编码序列（CDS）的37.9%。GacA还控制多种基因的表达，并调节多种表型，包括运动性和对氧化应激的抗性。与其他草本植物致病型菌株一样，GacA调节III型分泌系统和相关效应子的表达。此外，GacA还调节WHOP基因的表达，这些基因在从木本宿主分离的菌株中特异性编码，以及植物激素生物合成基因的表达。NCPPB 3335的一个突变体显示出毒力增加，产生带有高细菌群体的大的未成熟肿瘤，但在植物体内的竞争力显著降低。我们的结果进一步扩展了全局调节因子GacA在木本宿主病原体的毒力和适应性方面的作用。
