Barash Isaac, Manulis-Sasson Shulamit
Department of Plant Sciences, Faculty of Life Sciences, Tel-Aviv University, Tel-Aviv 61390, Israel.
Annu Rev Phytopathol. 2009;47:133-52. doi: 10.1146/annurev-phyto-080508-081803.
Pantoea agglomerans, a widespread epiphyte and commensal bacterium, has evolved into an Hrp-dependent and host-specific tumorigenic pathogen by acquiring a plasmid containing a pathogenicity island (PAI). The PAI was evolved on an iteron plasmid of the IncN family, which is distributed among genetically diverse populations of P. agglomerans. The structure of the PAI supports the premise of a recently evolved pathogen. This review offers insight into a unique model for emergence of new bacterial pathogens. It illustrates how horizontal gene transfer was the major driving force in the creation of the PAI, although a pathoadaptive mechanism might also be involved. It describes the crucial function of plant-produced indole-3-acetic acid (IAA) and cytokinines (CK) in gall initiation as opposed to the significant but secondary role of pathogen-secreted phytohormones. It also unveils the role of type III effectors in determination of host specificity and evolution of the pathogen into pathovars. Finally, it describes how interactions between the quorum sensing system, hrp regulatory genes, and bacterially secreted IAA or CKs affect gall formation and epiphytic fitness.
成团泛菌是一种广泛存在的附生菌和共生细菌，通过获得一个含有致病岛（PAI）的质粒，已进化成为一种依赖Hrp且具有宿主特异性的致瘤病原体。该致病岛是在IncN家族的迭代质粒上进化而来的，这种质粒分布在成团泛菌的遗传多样性群体中。致病岛的结构支持了一种最近进化出的病原体的前提。这篇综述深入探讨了新细菌病原体出现的独特模式。它说明了水平基因转移是致病岛形成的主要驱动力，尽管可能也涉及一种致病适应性机制。它描述了植物产生的吲哚 - 3 - 乙酸（IAA）和细胞分裂素（CK）在瘤形成中的关键作用，而病原体分泌的植物激素则起着重要但次要的作用。它还揭示了III型效应子在决定宿主特异性以及病原体向致病型变种进化过程中的作用。最后，它描述了群体感应系统、hrp调控基因与细菌分泌的IAA或CK之间的相互作用如何影响瘤的形成和附生适应性。
