Lu You, Ishimaru Carol A, Glazebrook Jane, Samac Deborah A
First and third authors: Department of Plant and Microbial Biology, second and fourth authors: Department of Plant Pathology, and first, second, third, and fourth authors: the Microbial and Plant Genomics Institute, University of Minnesota, St. Paul 55108; and fourth author: United States Department of Agriculture-Agricultural Research Service, Plant Science Research, St. Paul, MN 55108.
Phytopathology. 2018 Feb;108(2):172-185. doi: 10.1094/PHYTO-05-17-0171-R. Epub 2017 Dec 18.
Clavibacter michiganensis is the most economically important gram-positive bacterial plant pathogen, with subspecies that cause serious diseases of maize, wheat, tomato, potato, and alfalfa. Much less is known about pathogenesis involving gram-positive plant pathogens than is known for gram-negative bacteria. Comparative genome analyses of C. michiganensis subspecies affecting tomato, potato, and maize have provided insights on pathogenicity. In this study, we identified strains of C. michiganensis subsp. insidiosus with contrasting pathogenicity on three accessions of the model legume Medicago truncatula. We generated complete genome sequences for two strains and compared these to a previously sequenced strain and genome sequences of four other subspecies. The three C. michiganensis subsp. insidiosus strains varied in gene content due to genome rearrangements, most likely facilitated by insertion elements, and plasmid number, which varied from one to three depending on strain. The core C. michiganensis genome consisted of 1,917 genes, with 379 genes unique to C. michiganensis subsp. insidiosus. An operon for synthesis of the extracellular blue pigment indigoidine, enzymes for pectin degradation, and an operon for inositol metabolism are among the unique features. Secreted serine proteases belonging to both the pat-1 and ppa families were present but highly diverged from those in other subspecies.
密执安棒杆菌是经济上最重要的革兰氏阳性细菌植物病原体，其亚种可导致玉米、小麦、番茄、马铃薯和苜蓿发生严重病害。与革兰氏阴性细菌相比，人们对革兰氏阳性植物病原体致病机制的了解要少得多。对影响番茄、马铃薯和玉米的密执安棒杆菌亚种进行的比较基因组分析为致病性研究提供了见解。在本研究中，我们在模式豆科植物蒺藜苜蓿的三个品种上鉴定出了致病性不同的密执安棒杆菌亚种隐匿亚种菌株。我们生成了两个菌株的完整基因组序列，并将其与之前测序的一个菌株以及其他四个亚种的基因组序列进行比较。这三个密执安棒杆菌亚种隐匿亚种菌株由于基因组重排（很可能由插入元件促成）和质粒数量（因菌株而异，从一个到三个不等）而在基因含量上有所不同。密执安棒杆菌的核心基因组由1917个基因组成，其中379个基因是密执安棒杆菌亚种隐匿亚种所特有的。独特特征包括用于合成细胞外蓝色色素靛蓝的操纵子、用于果胶降解的酶以及用于肌醇代谢的操纵子。属于pat-1和ppa家族的分泌型丝氨酸蛋白酶均存在，但与其他亚种的蛋白酶差异很大。
