Pseudomonas syringae pv. eriobotryaeプラスミド上の病原性遺伝子psvAの分離と解析

上運 天博

doi:10.3186/jjphytopath.65.501

A pLAFR3 cosmid clone, pVIR6, which contains a virulence gene in the 23-kb insert DNA, was previously constructed. This virulence gene originated from the 52 Mdal plasmid of Pseudomonas syringae pv. eriobotryae. Serial deletion analyses of pVIR6 indicated that ca. 7kb of the insert DNA restored pathogenicity to an avirulent PE0 strain, and the deletion plasmid was designated as pKPN35. A 6961-bp insert DNA of pKPN35 was sequenced, and four possible reading frames (ORF1 480bp; ORF2 969bp; ORF3 2193bp; ORF4 516bp) were found in tandem. ORF1 and ORF4 had no significant homology to known genes. ORF2 had an amino acid sequence similar to the transposase of IS5 of E. coli. A recombinant plasmid pNSF1 containing only the ORF3 region restored pathogenicity to the avirulent PE0 strain. However, an ORF3 mutant of pNSF1, which was constructed by deleting a 580-bp BssHII segment from ORF3, failed to restore virulence to the same strain. Consequently, ORF3 was identified as a virulence gene and was named psvA. A HrpL-dependent promoter consensus sequence was found upstream of psvA. The psvA gene product was 731 amino acids long and had a predicted molecular mass of 83.2kDa. The deduced protein of the psvA gene showed no significant similarity to any protein sequence in the data base, although it had some similarity to the N-terminal region of the avrA gene in Pseudomonas syringae pv. glycinea. Production of the deduced protein of the psvA gene was confirmed in E. coli by using the expression vector pET-3a. Southern hybridization analysis indicated that the psvA gene was conserved in P. syringae pathovars myricae and dendropanacis which are causal agents of woody plant galls in Japan.

<i>Pseudomonas syringae</i> pv. <i>eriobotryae</i>プラスミド上の病原性遺伝子<i>psvA</i>の分離と解析

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