Structural comparison of the wild type and rfb303 mutant LPSs from Xanthomonas axonopodis pv. citri 35, 110

A. C. CASABUONO, ; S.PETROCELLI;; J. OTTADO; ; E. G.ORELLANO ; A. S. COUTO

San Luis

Congreso; XLVII Reunión Anual de la SAIB.; 2011

Sociedad Argentina de Investigaciones en Bioquimica y Biología Molecular

Xanthomonas axonopodis pv. citri (Xac) causes citrus canker, provoking defoliation and premature fruit drop with concomitant economical damage. In plant pathogenic bacteria, lipopolysaccharides (LPSs) are important virulence factors, and they are being increasingly recognized as major PAMPs for plants. We have previously characterized the LPS extracted from the Xac wild type and a wzt mutant. In the present work the LPS obtained from Xac-rfb303 defective in genes that codify for a glycosyltransferase involved in core synthesis was studied in order to get deeper in the role of Xac LPS in this disease.             LPSs from harvested cells were extracted with a 50% phenol/ water mixture. Purified LPS was hydrolyzed with 1% acetic acid, the precipitated lipid A was recovered by ultracentrifugation and the solution containing the sugar moiety (called oligosaccharide) was separated.  When the UV-MALDI-TOF ms analysis of the Lipid A obtained from rb303 was performed, a spectra showing similar species to the one obtained for the wild type Lipid A was detected. However, penta-acylated species bearing two pyrophosphoethanolamine groups were predominant. Total hydrolysis of the oligosaccharide moiety and HPAEC-PAD analysis revealed that the same monosacharides than the wild type were present, but in a different   relationship.  These structural differences were confirmed by UV-MALDI-TOF ms analysis.