Comparative Analysis of argK-tox Clusters and Their Flanking Regions in Phaseolotoxin-Producing Pseudomonas syringae Pathovars |
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| Authors: | Hiroyuki Genka Tomoya Baba Masataka Tsuda Shigehiko Kanaya Hirotada Mori Takanobu Yoshida Masako Tsujimoto Noguchi Kenichi Tsuchiya Hiroyuki Sawada |
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| Institution: | (1) Graduate School of Life Sciences, Tohoku University, Sendai, Japan;(2) Institute for Advanced Biosciences, Keio University, Tsuruoka, Yamagata, Japan;(3) Nara Institute of Science and Technology, Ikoma, Nara, Japan;(4) National Institute for Agro-Environmental Sciences, 3-1-3 Kannondai, Tsukuba Ibaraki, 305-8604, Japan;(5) National Agriculture Research Center for Western Region, Zentsuji, Kagawa, Japan;(6) Present address: National Institute of Agrobiological Sciences, 2-1-2 Kannondai, Tsukuba Ibaraki, 305-8602, Japan |
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| Abstract: | DNA fragments containing argK-tox clusters and their flanking regions were cloned from the chromosomes of Pseudomonas syringae pathovar (pv.) actinidiae strain KW-11 (ACT) and P. syringae pv. phaseolicola strain MAFF 302282 (PHA), and then their sequences were determined. Comparative analysis of these sequences and the sequences
of P. syringae pv. tomato DC3000 (TOM) (Buell et al., Proc Natl Acad Sci USA 100:10181–10186, 2003) and pv. syringae B728a (SYR) (Feil et al., Proc Natl Acad Sci USA 102:11064–11069, 2005) revealed that the chromosomal backbone regions of ACT and TOM shared a high similarity to each other but presented a low
similarity to those of PHA and SYR. Nevertheless, almost-identical DNA regions of about 38 kb were confirmed to be present
on the chromosomes of both ACT and PHA, which we named “tox islands.” The facts that the GC content of such tox islands was 6% lower than that of the chromosomal backbone regions of P. syringae, and that argK-tox clusters, which are considered to be of exogenous origin based on our previous studies (Sawada et al., J Mol Evol 54:437–457,
2002), were confirmed to be contained within the tox islands, suggested that the tox islands were an exogenous, mobile genetic element inserted into the chromosomes of P. syringae strains. It was also predicted that the tox islands integrated site-specifically into the homologous sites of the chromosomes of ACT and PHA in the same direction, respectively,
wherein 34 common gene coding sequences (CDSs) existed. Furthermore, at the left end of the tox islands were three CDSs, which encoded polypeptides and had similarities to the members of the tyrosine recombinase family,
suggesting that these putative site-specific recombinases were involved in the recent horizontal transfer of tox islands.
Electronic Supplementary Material Electronic Supplementary material is available for this article at
and accessible for authorised users. |
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| Keywords: | Pseudomonas syringae Pathovar phaseolicola Pathovar actinidiae Comparative analysis Phaseolotoxin argK-tox cluster Horizontal transfer Mobile genetic element tox island Tyrosine recombinase |
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