Rosenthal Emma, Potnis Neha, Bull Carolee T
Department of Plant Pathology and Environmental Microbiology, Pennsylvania State University, University Park, PA, United States.
Department of Entomology and Plant Pathology, Auburn University, Auburn, AL, United States.
Front Microbiol. 2022 Apr 18;13:840311. doi: 10.3389/fmicb.2022.840311. eCollection 2022.
Bacterial leaf spot (BLS) of lettuce caused by pv. () was first described over 100 years ago and remains a significant threat to lettuce cultivation today. This study investigated the genetic relatedness of the strains and the possible genetic sources of this race-specific pathogenicity. Whole genome sequences of eighteen strains representing the three races, along with eight related strains, were included in the analysis. A maximum likelihood phylogeny based on concatenated whole genome SNPs confirmed previous results describing two major lineages of strains. Gene clusters encoding secretion systems, secondary metabolites, and bacteriocins were assessed to identify putative virulence factors that distinguish the races. Genome sequences were mined for effector genes, which have been shown to be involved in race specificity in other systems. Two effectors identified in this study, and the novel variant , were revealed as possible mediators of a gene-for-gene interaction between race 1 and 3 strains and wild lettuce ARM-09-161-10-1. Transposase sequence identified downstream of and prophage sequence found nearby within race 1 and 3 insertion sequences suggest that this gene may have been acquired through phage-mediated gene transfer. No other factors were identified from these analyses that distinguish the races.
由生菜叶斑病菌（Xanthomonas campestris pv. vitians）引起的生菜细菌性叶斑病在100多年前就首次被描述，如今仍然是生菜种植的重大威胁。本研究调查了生菜叶斑病菌株的遗传相关性以及这种小种特异性致病性的可能遗传来源。分析中纳入了代表三个小种的18个生菜叶斑病菌株的全基因组序列，以及8个相关菌株。基于串联全基因组单核苷酸多态性的最大似然系统发育分析证实了先前描述生菜叶斑病菌株两个主要谱系的结果。对编码分泌系统、次生代谢产物和细菌素的基因簇进行了评估，以鉴定区分生菜叶斑病菌小种的假定毒力因子。对基因组序列进行挖掘以寻找效应子基因，这些基因已被证明在其他系统中参与小种特异性。本研究中鉴定出的两个效应子，即XopAG1和新变体XopAG1v2，被揭示可能是小种1和3菌株与野生生菜ARM-09-161-10-1之间基因对基因相互作用的介导因子。在小种1和3插入序列中，在XopAG1下游鉴定到的转座酶序列以及在其附近发现的前噬菌体序列表明，该基因可能是通过噬菌体介导的基因转移获得的。这些分析未鉴定出其他区分生菜叶斑病菌小种的因子。
