Identification of genetic and environmental factors stimulating excision from XXXX chromosome of the toxicogenic region responsible for pathogenicity.

@entity9250 @entity1138 @entity415 @entity25068 @entity71733
UNASSIGNED: The genes conferring pathogenicity in @entity25068 turgidiscabies, a pathogen causing common scab of @entity415 , are grouped together on a pathogenicity island (PAI), which has been found to be mobile and appears to transfer and disseminate like an integrative and conjugative element (ICE). However, in @entity9250 , another common scab-inducing species, the pathogenicity genes are clustered in two regions: the toxicogenic region (TR) and the colonization region. The @entity71733 genome was analysed to investigate the potential mobility of the TR. Attachment sites (att), short homologous sequences that delineate ICEs, were identified at both extremities of the TR. An internal att site was also found, suggesting that the TR has a composite structure (TR1 and TR2). Thaxtomin biosynthetic genes, essential for pathogenicity, were found in TR1, whereas candidate genes with known functions in recombination, replication and conjugal transfer were found in TR2. Excision of the TR1 or TR2 subregions alone, or of the entire TR region, was observed, although the excision frequency of TR was low. However, the excision frequency was considerably increased in the presence of either @entity1138 or @entity25068 cells. A composite TR structure was not observed in all @entity9250 and @entity25068 acidiscabies strains tested. Of the ten strains analysed, seven lacked TR2 and no TR excision event could be detected in these strains, thus suggesting the implication of TR2 in the mobilization of @entity9250   TR.
