Dept. of Plant Pathology and Weed Research, Agricultural Research Organization-Volcani Institute, Rishon LeZion, Israel.
Dept. Of Plant Pathology and Environmental Microbiology, Pennsylvania State University, University Park, Pennsylvania, United States of America.
PLoS Pathog. 2024 Jul 19;20(7):e1012380. doi: 10.1371/journal.ppat.1012380. eCollection 2024 Jul.
Plant pathogenic bacteria often have a narrow host range, which can vary among different isolates within a population. Here, we investigated the host range of the tomato pathogen Clavibacter michiganensis (Cm). We determined the genome sequences of 40 tomato Cm isolates and screened them for pathogenicity on tomato and eggplant. Our screen revealed that out of the tested isolates, five were unable to cause disease on any of the hosts, 33 were exclusively pathogenic on tomato, and two were capable of infecting both tomato and eggplant. Through comparative genomic analyses, we identified that the five non-pathogenic isolates lacked the chp/tomA pathogenicity island, which has previously been associated with virulence in tomato. In addition, we found that the two eggplant-pathogenic isolates encode a unique allelic variant of the putative serine hydrolase chpG (chpGC), an effector that is recognized in eggplant. Introduction of chpGC into a chpG inactivation mutant in the eggplant-non-pathogenic strain Cm101, failed to complement the mutant, which retained its ability to cause disease in eggplant and failed to elicit hypersensitive response (HR). Conversely, introduction of the chpG variant from Cm101 into an eggplant pathogenic Cm isolate (C48), eliminated its pathogenicity on eggplant, and enabled C48 to elicit HR. Our study demonstrates that allelic variation in the chpG effector gene is a key determinant of host range plasticity within Cm populations.
植物病原菌通常具有狭窄的宿主范围，这在种群内的不同分离株之间可能有所不同。在这里，我们研究了番茄病原菌 Clavibacter michiganensis (Cm) 的宿主范围。我们确定了 40 个番茄 Cm 分离株的基因组序列，并筛选了它们对番茄和茄子的致病性。我们的筛选结果表明，在所测试的分离株中，有 5 个不能引起任何宿主的疾病，33 个仅对番茄具有致病性，还有 2 个能够感染番茄和茄子。通过比较基因组分析，我们发现这 5 个非致病性分离株缺乏以前与番茄毒力相关的 chp/tomA 致病性岛。此外，我们发现，这两个茄子致病性分离株编码了假定丝氨酸水解酶 chpG（chpGC）的独特等位基因变异体，该效应物在茄子中被识别。将 chpGC 引入茄子非致病性菌株 Cm101 的 chpG 失活突变体中，未能互补突变体，该突变体仍能在茄子中引起疾病，且不能引发过敏反应 (HR)。相反，将 chpG 变体从 Cm101 引入茄子致病性 Cm 分离株 (C48) 中，消除了其对茄子的致病性，并使 C48 能够引发 HR。我们的研究表明，chpG 效应基因的等位基因变异是 Cm 种群宿主范围可塑性的关键决定因素。
