In order to identify of proteins involved in the pathogenicity of the plant pathogen Xanthomonas axonopodis pv. citri, we compared the proteome of the bacteria in different conditions. Protein extracts obtained from non-infecting Xac grown on nutrient broth medium and infecting Xac grown on host plant for 3 or 5 days after inoculation, were analyzed by 2-dimensional liquid chromatography-tandem mass spectrometry (2D-LC-MS/MS).
Within the genus Xanthomonas, several genes have been found associated with pathogenicity and virulence. Among these genes, the avr (avirulence), rpf (named for regulation of pathogenicity factors), and hrp (named for hypersensitive response and pathogenicity) are perhaps the most widely studied elements.
Data analysis indicated 267 proteins potentially associated with pathogenicity and virulence. Twenty-two of these proteins are related to pathogenicity, virulence and adaptation (expressed 3 days after inoculation):
XAC0011 (biopolymer transport ExbD2 protein), XAC0030 (cellulase), XAC0210 (superoxide dismutase), XAC0282 (organic hydroperoxide resistance protein), XAC0393 (HpaF protein), XAC0411 (HrpB5 protein), XAC0415 (HrcC protein), XAC0618 (periplasmic glucan biosynthesis protein), XAC0906 (alkyl hydroperoxide reductase subunit F), XAC1368 (virulence protein), XAC1465 (major cold shock protein), XAC1567 (RNase R), XAC2499 (multidrug efflux transporter), XAC2513 (queuine tRNA-ribosyltransferase), XAC2844 (multidrug resistance protein), XAC3209 (trehalose-6-phosphate phosphatase), XAC3304 (sulfur deprivation response regulator), XAC3450 (gamma-glutamyltranspeptidase), XAC3543 (general secretion pathway protein F), XAC3544 (general secretion pathway protein E), XAC4370 (thiophene and furan oxidation protein), XACb0037 (VirB11 protein).
The superoxide dismutase, organic hydroperoxide resistance protein and major cold shock protein, expressed only 3 days after inoculation, allowed the cells to adapt to the new environment. Some functions of the adaptative and survival responses play roles in the pathogenicity of the bacteria.
Among these proteins, we also found 60 proteins originally annotated as conserved hypothetical and these proteins are probably involved in the adaptation process or pathogen and plant interaction.
Our data, of the different proteomes of the Xac, provide information that contribute to a more complete understanding of the pathogen and host plant interaction.
Financial Support: FAPESP and FUNDECITRUS