Multiple plasmid‐borne virulence genes of <italic>Clavibacter michiganensis</italic> ssp. <italic>capsici</italic> critical for disease development in pepper.

Summary: <italic>Clavibacter michiganensis</italic> ssp. <italic>capsici</italic> is a Gram‐positive plant‐pathogenic bacterium causing bacterial canker disease in pepper. Virulence genes and mechanisms of <italic>C. michiganensis</italic> ssp. <italic>capsici</italic> in pepper have not yet been studied. To identify virulence genes of <italic>C. michiganensis</italic> ssp. <italic>capsici</italic>, comparative genome analyses with <italic>C. michiganensis</italic> ssp. <italic>capsici</italic> and its related <italic>C. michiganensis</italic> subspecies, and functional analysis of its putative virulence genes during infection were performed. The <italic>C. michiganensis</italic> ssp. <italic>capsici</italic> type strain PF008 carries one chromosome (3.056 Mb) and two plasmids (39 kb pCM1_Cmc and 145 kb pCM2_Cmc). The genome analyses showed that this bacterium lacks a chromosomal pathogenicity island and <italic>celA</italic> gene that are important for disease development by <italic>C. michiganensis</italic> ssp. <italic>michiganensis</italic> in tomato, but carries most putative virulence genes in both plasmids. Virulence of pCM1_Cmc‐cured <italic>C. michiganensis</italic> ssp. <italic>capsici</italic> was greatly reduced compared with the wild‐type strain in pepper. The complementation analysis with pCM1_Cmc‐located putative virulence genes showed that at least five genes, <italic>chpE</italic>,<italic> chpG</italic>,<italic> ppaA1</italic>,<italic> ppaB1</italic> and <italic>pelA1</italic>, encoding serine proteases or pectate lyase contribute to disease development in pepper. In conclusion, <italic>C. michiganensis</italic> ssp. <italic>capsici</italic> has a unique genome structure, and its multiple plasmid‐borne genes play critical roles in virulence in pepper, either separately or together. [ABSTRACT FROM AUTHOR]