Hojo Hiroshi, Koyanagi Makoto, Tanaka Masayuki, Kajihara Shigeru, Ohnishi Kouhei, Kiba Akinori, Hikichi Yasufumi
Laboratory of Plant Pathology and Biotechnology, Kochi University, 200 Monobe, Nankoku, Kochi 783-8502, Japan.
Institute of Molecular Genetics, Kochi University, 200 Monobe, Nankoku, Kochi 783-8502, Japan.
Microbiology (Reading). 2008 Oct;154(Pt 10):2920-2928. doi: 10.1099/mic.0.2008/021097-0.
Pseudomonas cichorii causes necrotic lesions in eggplant and rot in lettuce. Through transposon insertion into P. cichorii strain SPC9018 we produced two mutants, 4-57 and 2-99, that lost virulence on eggplant but not lettuce. Analyses showed that a transposon was inserted into the hrpG gene in 4-57 and the hrcT gene in 2-99. Nucleotide sequences of the hrp genes of SPC9018 are homologous to those of Pseudomonas viridiflava BS group strains. The pathogenicity of 4-57 on eggplant was restored by transformation with an hrpF operon, originating from either SPC9018 or the BS group member P. viridiflava strain 9504 (Pv9504). These data suggested the involvement of hrp genes in the pathogenicity of SPC9018 on eggplant, and functional conservation of hrpF operons between SPC9018 and Pv9504. Both the hrpS mutant and the hrpL mutant were unable to cause necrotic lesions on eggplant leaves but retained their pathogenicity against lettuce. These results suggest that the pathogenicity of P. cichorii is hrp-dependent in eggplant, but not in lettuce.
菊苣假单胞菌可导致茄子出现坏死性病变以及生菜腐烂。通过转座子插入菊苣假单胞菌菌株SPC9018，我们获得了两个突变体，4-57和2-99，它们对茄子失去了毒力，但对生菜仍有毒力。分析表明，转座子在4-57中插入了hrpG基因，在2-99中插入了hrcT基因。SPC9018的hrp基因核苷酸序列与绿黄假单胞菌BS组菌株的同源。用源自SPC9018或BS组成员绿黄假单胞菌菌株9504（Pv9504）的hrpF操纵子转化，恢复了4-57对茄子的致病性。这些数据表明hrp基因参与了SPC9018对茄子的致病性，以及SPC9018和Pv9504之间hrpF操纵子的功能保守性。hrpS突变体和hrpL突变体都不能在茄子叶片上引起坏死性病变，但对生菜仍保留致病性。这些结果表明，菊苣假单胞菌对茄子的致病性依赖hrp基因，但对生菜则不然。
