An H-NS-like protein involved in the negative regulation of hrp genes in Xanthomonas oryzae pv. oryzae

Author： Kametani-Ikawa Yumi Tsuge Seiji Furutani Ayako Ochiai Hirokazu

ISSN： 0378-1097

Source： FEMS Microbiology Letters, Vol.319, Iss.1, 2011-06, pp. : 58-64

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Abstract

Abstracthrp genes encode components of a type III secretion (T3S) system and play crucial roles in the pathogenicity of the rice pathogen Xanthomonas oryzae pv. oryzae (Xoo). A histone-like nucleoid-structuring (H-NS) protein binds DNA and acts as a global transcriptional repressor. Here, we investigated the involvement of an h-ns-like gene, named xrvB, in the expression of hrp genes in Xoo. Under the hrp-inducing culture condition, the expression of a key hrp regulator HrpG increased in the XrvB mutant, followed by activation of the downstream gene expression. Also, in planta, the secretion of a T3S protein (XopR) was activated by the mutation in xrvB. Gel retardation assay indicated that XrvB has DNA-binding activity, but without a preference for the promoter region of hrpG. The results suggest that XrvB negatively regulates hrp gene expression and that an unknown factor(s) mediates the regulation of hrpG expression by XrvB.