Genetic diversity ofPseudomonas syringaepv.actinidiae, pathogen of kiwifruit bacterial canker

Abstract

Bacterial canker disease of kiwifruit currently occurs in at least 15 countries, causing serious damage. The causative agent of the disease is Pseudomonas syringae pv. actinidiae (Psa), which is genetically diverse and is currently classified into five biovars, namely, biovars 1, 2, 3, 5 and 6. In Japan, four biovars except biovar 2 have been found so far. These biovars have been confirmed to have differences in the virulence and composition of pathogenicity‐related genes, such as toxin biosynthesis and type III effector genes. Biovars 1 and 6 possess the tox island, a genomic island of approximately 38 kb, which contains phaseolotoxin biosynthesis genes (argK‐tox cluster) and is confirmed to have been acquired from other bacteria through horizontal transfers. Also, on the megaplasmid possessed by biovar 6, there exist coronatine biosynthesis genes, and biovar 6 has the ability to produce two phytotoxins, phaseolotoxin and coronatine. In 2014, biovar 3, considered to be of foreign origin, was confirmed for the first time in Japan. Biovar 5, whose virulence is relatively weak, is distributed only in a limited area. In addition to the tox island and various plasmids, a large number of mobile genetic elements are confirmed to be present on the Psa genomes, which might have played a major role in helping Psa to acquire new features. In order to understand how Psa acquired the ability to infect kiwifruit systemically, it is important to make polyphasic comparisons with related pathovars, such as P. syringae pv. theae and pv. actinidifoliorum.

Phytotoxin synthesis genes and type III effector genes of Pseudomonas syringae pv. actinidiae biovar 6 are regulated by culture conditions

“…It has been further classified into biovar 1, 2, 3, 5, and 6, reflecting its physiological and genetic diversity ( Chapman et al, 2012 ; Fujikawa & Sawada, 2016 ; Fujikawa & Sawada, 2019 ; Sawada & Fujikawa, 2019a ; Sawada & Fujikawa, 2019b ). In Japan, Psa is highly diverse, with significant differences in the types or presence of phytotoxins produced among biovars ( Sawada & Fujikawa, 2019a ; Sawada & Fujikawa, 2019b ). In general, the plant pathogenic bacteria group, P. syringae, is highly differentiated in pathogenicity, and it is known to have more than 60 different pathovars with different host plants and symptoms ( Sawada, 2014 ).…”

“…Although the core genome sequences of Psa are almost the same among biovars, the presence and combination of phytotoxins and effector genes are diverse. Therefore, the diversity of effectors and phytotoxins may be due to accessory genomes encoded by transposons and other mobile genetic elements ( Sawada & Fujikawa, 2019a ; Sawada & Fujikawa, 2019b ).…”

Phytotoxin synthesis genes and type III effector genes ofPseudomonas syringaepv.actinidiaebiovar 6 are regulated by culture conditions

“…It has been further classified into biovar 1, 2, 3, 5, and 6, reflecting its physiological and genetic diversity ( Chapman, et al, 2012; Fujikawa & Sawada, 2016; 2019; Sawada & Fujikawa, 2019a; 2019b ). In Japan, Psa is highly diverse, with significant differences in the types or presence of phytotoxins produced among biovars ( Sawada & Fujikawa, 2019a; 2019b ). In general, the plant pathogenic bacteria group, P. syringae , is highly differentiated in pathogenicity, and it is known to have more than 60 different pathovars with different host plants and symptoms ( Sawada, 2014 ).…”

“…Although the core genome sequences of Psa are almost the same among biovars, the presence and combination of phytotoxins and effector genes are diverse. Therefore, the diversity of effectors and phytotoxins may be due to accessory genomes encoded by transposons and other mobile genetic elements ( Sawada & Fujikawa, 2019a; 2019b ).…”

Peer Review #1 of "Phytotoxin synthesis genes and type III effector genes of Pseudomonas syringae pv. actinidiae biovar 6 are regulated by culture conditions (v0.2)"

“…It has been further classified into biovar 1, 2, 3, 5, and 6, reflecting its physiological and genetic diversity (Chapman, et al, 2012;Fujikawa & Sawada, 2016;2019;Sawada & Fujikawa, 2019a;2019b). In Japan, Psa is highly diverse, with significant differences in the types or presence of phytotoxins produced among biovars (Sawada & Fujikawa, 2019a;2019b). In general, the plant pathogenic bacteria group, P. syringae, is highly differentiated in pathogenicity, and it is known to have more than 60 different pathovars with different host plants and symptoms (Sawada, 2014).…”