Novel oligosaccharides isolated from Fusarium oxysporum L. rapidly induce PAL activity in Rubus cells.

Activation of the phenolic pathway is known to be part of a defense response against cell wall-derived elicitors from pathogens. Many examples of a defense response by increasing the synthesis of phenolic compound against the elicitor were demonstrated in the past, but the elicitor structure has so far been poorly characterized. Our results indicate that a disaccharide fraction containing the following structure: alpha-D-mannopyranosyl (1-->2)alpha/beta-D-glucopyranosyl and alpha-D-mannopyranosyl (1-->x) inositol, isolated from Fusarium oxysporum L., promotes rapid and transient phenylalanine ammonia lyase activity in Rubus fructicosus cells at nanomolar concentration. The disaccharides were isolated by size-exclusion chromatography directly from extracts obtained by alkaline treatment of F. oxysporum mycelium. Their structure was determined by 500-MHz-1H-NMR spectroscopy combined with methylation analysis and fast atom bombardment mass spectrometry.

High performance liquid chromatography and photodiode array detection of ferulic acid in Rubus protoplasts elicited by O-glycans from Fusarium sp. M7-1.

So far only little data have been available concerning the eliciting capacity of well defined glycan molecules isolated from plant pathogens. This study brings new information about changes in plant cells caused by fungal pathogens. Sugar fractions derived from glycoproteins isolated from the fungus Fusarium sp. M7-1 have been tested here as signaling molecules. The ability of three O-glycan fractions (named in this work inducer I, II, III) to trigger responses in Rubus protoplasts has been examined. It was found that inducer III was the most efficient as it elicited changes in the levels of phenylpropanoid pathway intermediates in relation to phenylalanine-ammonia lyase (PAL) activation.