Effects of the C-terminal alternative addition of amino acids on the gene regulatory activity of the LysR-type transcriptional regulator PhcA in Ralstonia pseudosolanacearum strain OE1-1

In the quorum sensing-active state, the phytopathogenic Ralstonia pseudosolanacearum strain OE1-1 activates the 347-amino acid LysR-type transcriptional regulator PhcA, which regulates PhcA-regulated genes responsible for its virulence. To elucidate the functional role of the PhcA C-terminus, the phcA -deletion strain was transformed with a truncated phcA encoding PhcA lacking only the 20 C-terminal amino acids or a frameshift-mutated phcA carrying a single adenine deletion at position 983. The frameshift-mutation but not truncation of PhcA C-terminus affected the regulation of PhcA-regulated genes, losing virulence. These results indicate that the frameshift-derived amino acid additions at the C-terminus impair PhcA’s regulatory function.