抄録
The bacterium Dickeya dadantii causes soft-rot diseases in many plants. Analysis of LfaR, a LacI-family transcriptional regulator of the D. dadantii 3927 strain, revealed its involvement in the plant pathogenicity of the D. dadantii. We first identified a protein that bound to the pelE promoter region of a phytopathogen Dickeya chrysanthemi (formerly Erwinia chrysanthemi) strain EC16 under hyperinduction by pectate lyase in a gel-shift assay. The protein purified with a heparin column was analyzed by time-of-flight mass spectrometry and revealed to be a ~40 kDa protein in the LacI repressor family. To elucidate the contribution of this novel protein to plant pathogenesis, we investigated the lfaR gene, which encodes the homolog of the novel protein in the genome of D. dadantii (formerly E. chrysanthemi) strain 3937. The marker-exchanged mutant of lfaR, constructed using the strain 3937, showed an increased ability to macerate potato tubers, Chinese cabbage leaves, and witloof chicory leaves. The lfaR mutant of strain 3937 also had an increased capacity to synthesize major extracellular enzymes, namely pectate lyase, polygalacturonase, cellulase, and protease. Other determinants of pathogenicity, such as motility and synthesis of the blue pigment indigoidine, were enhanced in this mutant. Thus, we considered that this regulatory protein negatively modulates the regulation of extracellular enzymes and other virulence factors. Interestingly, in D. dadantii 3937, LfaR regulated the transcription of adjacent genes, including lfaA, but not the distantly located gene pelE. Differences in genome organization and the nucleotide sequence of the promoter region of the pelE gene between D. chrysanthemi and D. dadantii may explain the differences in the genes regulated by their LfaR homologs.
https://ror.org/024exxj48 
