Elicitor and resistance-inducing activities of -1,4 cellodextrins in grapevine, comparison with -1,3 glucans and -1,4 oligogalacturonides
Résumé
Cellodextrins (CD), water-soluble derivatives of cellulose composed of b-1,4 glucoside residues, have been shown to induce a variety of defence responses in grapevine (Vitis vinifera L.) cells. The larger oligomers of CD rapidly induced transient generation of H2O2 and elevation in free cytosolic calcium, followed by a differential expression of genes encoding key enzymes of the phenylpropanoid pathway and pathogenesisrelated (PR) proteins as well as stimulation of chitinase and b-1,3 glucanase activities. Most of these defence reactions were also induced by linear b-1,3 glucans (bGlu) and a-1,4 oligogalacturonides (OGA) of different degree of polymerization (DP), but the intensity of some reactions induced by CD was different when compared with bGlu and OGA effects. Moreover, desensitization assays using H2O2 production showed that cells treated with CD remained fully responsive to a second application of OGA, suggesting a different mode of perception of these oligosaccharides by grape cells. None of CD, bGlu, or OGA induced HSR gene expression nor did they induce cell death. In accordance with elicitor activity in grapevine cells, CD-incubated leaves challenged with Botrytis cinerea also resulted in a significant reduction of the disease. Data suggest that CD could operate via other distinct reaction pathways than bGlu and OGA. They also highlight the requirement of a specific DP for each oligosaccharide to induce the defence response.