The Pseudomonas savastanoi pv. savastanoi AraC-family transcriptional regulator WhpR controls virulence in woody hosts through positive regulation of indole compounds

The genome of the olive tree pathogen Pseudomonas savastanoi pv. savastanoi (Psv) NCPPB 3335 encodes a region of about 15 kb named WHOP (from Woody Host and Pseudomonas) which is involved in the catabolism of aromatic compounds and is essential for the virulence of Psv in woody olive plants. This region is shared with other strains of Pseudomonas syringae pathovars infecting woody hosts, but it is absent in strains infecting herbaceous plants. The WHOP region is organized into four operons, antABC (metabolism of anthranilate), catBCA (catabolism of catechol) ipoBCA and dhoAB and three independently transcribed genes, antR (positive regulator of the antABC operon), PSA3335_3206 (aerotaxis receptor) and whpR (putative AraC family regulator). The aim of these study: to determine the role of the dhoAB e ipoABC operons, and to investigate the role of WhpR in gene regulation and virulence.