Hrpm is involved in glucan biosynthesis, biofilm formation and pathogenicity in Xanthomonas citri ssp. citri

MALAMUD F; CONFORTE VP; RIGANO LA; CASTAGNARO AP; MARANO MR; ALEXANDRE M DO AMARAL

MOLECULAR PLANT PATHOLOGY

WILEY-BLACKWELL PUBLISHING, INC

Año: 2012 p. 1010 - 1018

1464-6722

Xanthomonas citri ssp. citri (Xcc) is the causal agent of citruscanker. This bacterium develops a characteristic biofilm on bothbiotic and abiotic surfaces. A biofilm-deficient mutant was identifiedin a screening of a transposon mutagenesis library of the Xcc306 strain constructed using the commercial Tn5 transposonEZ-Tn5 Tnp Transposome (Epicentre). Sequence analysisof a mutant obtained in the screening revealed that a single copyof the EZ-Tn5 was inserted at position 446 of hrpM, a geneencoding a putative enzyme involved in glucan synthesis. Wedemonstrate for the first time that the product encoded by thehrpM gene is involved in b-1,2-glucan synthesis in Xcc.A mutationin hrpM resulted in no disease symptoms after 4 weeks of inoculationin lemon and grapefruit plants. The mutant also showedreduced ability to swim in soft agar and decreased resistance toH2O2 in comparison with the wild-type strain. All defective phenotypeswere restored to wild-type levels by complementation withthe plasmid pBBR1-MCS containing an intact copy of the hrpMgene and its promoter. These results indicate that the hrpM genecontributes to Xcc growth and adaptation in its host plant.