INDUCTION OF EXTRACELLULAR-MATRIX GLYCOPROTEINS IN BRASSICA PETIOLES BY WOUNDING AND IN RESPONSE TO XANTHOMONAS-CAMPESTRIS

A panel of monoclonal antibodies that recognize plant extracellular ma trix glycoproteins previously implicated in plant-microbe interactions was used to study the effects of pathogen inoculation and wounding on glycoproteins in petioles of Brassica campestris. The panel of monocl onal comprised two sets: JIM11, JIM12, and JIM20 recognize epitopes ca rried on hydroxyproline-rich glycoproteins (HRGPs) (M. Smallwood, A. B even, N. Donovan, S. J. Neill, J. Peart, K. Roberts, and J. P. Knox, P lant J. 5:237-246, 1994); MAC204 and MAC265 recognize glycoproteins of the Rhizobium infection thread (K. A. VandenBosch, D. J. Bradley, S. Perotto, G. W. Butcher, and N. J. Brewin, EMBO J. 8:335-342, 1989). Wo unding or inoculation of petioles with avirulent strains of pathovars of Xanthomonas campestris induced the synthesis of two new groups of a ntigens: gp160 ran as a smear on sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE) with apparent molecular mass from 120 to 200 kDa and was recognized by JIM20 and MAC204; gpS remained in the stacking gel on SDS-PAGE and was recognized by JIM11, JIM20, and MAC2 04. The response to virulent strains of pathovars of X. campestris was either less pronounced or absent. gpS comprised several components th at were resolved by cation-exchange chromatography. Some of these comp onents were characterized as extensin-like HRGPs. The level of inducti on of the gpS group of antigens by virulent strains was not altered by mutation of a number of genes required for basic pathogenicity or by heat-killing the bacteria.