ARS | Publication request: CELL WALL MODELING, PEROXIDASE EXPRESSION AND APOPLASTIC LEVELS OF CARBOHYDRATES IN A PATHOGENIC ASSOCIATION WITH A FUNGAL ENDOPHYTE IN WHEAT SHEATHS

Submitted to: Plant Physiology Supplement
Publication Type: Abstract Only
Publication Acceptance Date: July 1, 1998
Publication Date: N/A

Technical Abstract: Plant cell walls are dynamic structures that play important roles in recognition, signaling and plant defense responses against pathogens. The relationship between the biochemical and molecular changes in cell walls during a pathogenic association with an endophytic fungus, an Acremonium spp., was investigated in wheat (Triticum aestivum L) sheaths. Altered apoplastic peroxidase isoenzymes, peroxidase gene expression, localization of cell wall structural proteins, levels of wall-bound ferulic (FA) and diferulic (DFA) acids and apoplastic carbohydrates were examined in relation to wall remodeling. Increases in total dimers (DFA) and also in ether-linked ferulates, which correlate directly to increases in lignification were found in Acremonium-infected sheaths. Laser scanning confocal microscopy was used to assess changes in cell wall structural proteins using monoclonal antibodies to HRGP (JIM13) and a cationic peroxidase (K46). Increases in activities and the induction of unique anionic and cationic apoplastic peroxidases were discovered in the infected sheaths. Peroxidase transcript accumulation was discretely localized to the xylem elements, schlerenchyma tissues contained within the vascular bundles, and to the sites of fungal penetration/infection in the sheath tissues. Identification and quantification of apoplastic carbohydrates correspond with the pathogenic form of this endophytic fungus. We propose that alterations in cell wall-peroxidases in Acremonium-infected sheaths evoke oxidative coupling reactions associated with the remodeling of the cell wall in response to pathogen attack. Supported by grants awarded to A.J.A. from NASA Small Payload and to D.L.B from NASA Centers grant NGT10- 52609.