Disease relevance of phcA

• Host plant-dependent phenotypic reversion of Ralstonia solanacearum from non-pathogenic to pathogenic forms via alterations in the phcA gene [1].
• Here, we report discovery of a phcA orthologue in the non-pathogenic, facultative chemolithoautotroph Ralstonia eutropha (Alcaligenes eutrophus) that fully complements R. solanacearum phcA mutants [2].
• Cloning of wild-type Pseudomonas solanacearum phcA, a gene that when mutated alters expression of multiple traits that contribute to virulence [3].

High impact information on phcA

• PC is often associated with mutations in phcA, which is a key virulence regulatory gene [1].
• Similarly, in broth culture, expression of a pilA::lacZ fusion in AW1 decreased 10-fold at high cell density, but expression remained high in a phcA mutant [4].
• Relative to their wild-type parents, phcA mutants overproduced iron-scavenging activity detected with chrome azurol S siderophore detection medium [5].
• During a spontaneous phenotype conversion event, the promoter of the phcA gene was interrupted by one of these IS elements [6].
• Production of the PhcA-regulated factors exopolysaccharide I, endoglucanase, and pectin methyl esterase was reduced 10- to 100-fold only in mutants with a nonpolar insertion in phcB [which express phcSR(Q) in the absence of the EF]; simultaneously, expression of phcA was reduced fivefold [7].

Biological context of phcA

• The wild-type region containing the gene that controls traits affected by phenotype conversion in AW1, designated phcA, was cloned on a 2.2-kb DNA fragment that restored all the phcA::Tn5 mutants and 11 independent spontaneous PC-type derivatives of AW1 to wild-type status [3].
• The DNA sequence of a 1.8-kb region from strain AW1 that contains phcA revealed one open reading frame that should encode a polypeptide of 38.6 kDa [8].

Analytical, diagnostic and therapeutic context of phcA

• Sequence analysis of phcA1 and chimeric constructs of phcA and phcA1 confirmed that PhcA1 is truncated by a 2-bp insertion 147 nucleotides upstream of the carboxyl terminus of PhcA [8].
• Southern blot analysis of 10 additional independently isolated PC mutants of strain AW1 revealed that two strains have larger insertions (0.2 and 1.0 kb) within phcA [8].

References