Aragón Isabel M, Pérez-Martínez Isabel, Moreno-Pérez Alba, Cerezo Miguel, Ramos Cayo
Área de Genética, Facultad de Ciencias, Instituto de Hortofruticultura Subtropical y Mediterrnea "La Mayora", Universidad de Málaga-CSIC (IHSM-UMA-CSIC), Málaga, Spain.
FEMS Microbiol Lett. 2014 Jul;356(2):184-92. doi: 10.1111/1574-6968.12413. Epub 2014 Mar 24.
Indole-3-acetic acid (IAA) is a widespread phytohormone among plant-associated bacteria, including the tumour-inducing pathogen of woody hosts, Pseudomonas savastanoi pv. savastanoi. A phylogenetic analysis of the iaaM/iaaH operon, which is involved in the biosynthesis of IAA, showed that one of the two operons encoded by Pseudomonas savastanoi pv. savastanoi NCPPB 3335, iaaM-1/iaaH-1, is horizontally transferred among bacteria belonging to the Pseudomonas syringae complex. We also show that biosynthesis of the phytohormone, virulence and full fitness of this olive pathogen depend only on the functionality of the iaaM-1/iaaH-1 operon. In contrast, the iaaM-2/iaaH-2 operon, which carries a 22-nt insertion in the iaaM-2 gene, does not contribute to the production of IAA by this bacterium. A residual amount of IAA was detected in the culture supernatants of a double mutant affected in both iaaM/iaaH operons, suggesting that a different pathway might also contribute to the total pool of the phytohormone produced by this pathogen. Additionally, we show that exogenously added IAA negatively and positively regulates the expression of genes related to the type III and type VI secretion systems, respectively. Together, these results suggest a role of IAA as a signalling molecule in this pathogen.
吲哚 - 3 - 乙酸（IAA）是一种在与植物相关的细菌中广泛存在的植物激素，包括木本宿主的致瘤病原体——丁香假单胞菌 savastanoi 致病变种（Pseudomonas savastanoi pv. savastanoi）。对参与IAA生物合成的iaaM/iaaH操纵子进行系统发育分析表明，丁香假单胞菌 savastanoi 致病变种NCPPB 3335编码的两个操纵子之一，iaaM - 1/iaaH - 1，在丁香假单胞菌复合体的细菌之间进行水平转移。我们还表明，这种橄榄病原体的植物激素生物合成、毒力和完全适应性仅取决于iaaM - 1/iaaH - 1操纵子的功能。相比之下，iaaM - 2/iaaH - 2操纵子在iaaM - 2基因中有一个22个核苷酸的插入，对该细菌产生IAA没有贡献。在两个iaaM/iaaH操纵子均受影响的双突变体的培养上清液中检测到残留量的IAA，这表明不同的途径可能也对该病原体产生的植物激素总量有贡献。此外，我们表明外源添加的IAA分别对与III型和VI型分泌系统相关的基因表达产生负调控和正调控。总之，这些结果表明IAA在这种病原体中作为信号分子发挥作用。
