Elicitor and resistance-inducing activities of {szligbeta}-1,4 cellodextrins in grapevine, comparison with {szligbeta}-1,3 glucans and alpha -1,4 oligogalacturonides

Cellodextrins (CD), water-soluble derivatives of cellulose composed of {szligbeta}-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 H sub(2)O sub(2) and elevation in free cytosolic calcium, followed by a differential expression of genes encoding key enzymes of the phenylpropanoid pathway and pathogenesis-related (PR) proteins as well as stimulation of chitinase and {szligbeta}-1,3 glucanase activities. Most of these defence reactions were also induced by linear {szligbeta}-1,3 glucans ({szligbeta}Glu) and alpha -1,4 oligogalacturonides (OGA) of different degree of polymerization (DP), but the intensity of some reactions induced by CD was different when compared with {szligbeta}Glu and OGA effects. Moreover, desensitization assays using H sub(2)O sub(2) 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, {szligbeta}Glu, 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 {szligbeta}Glu and OGA. They also highlight the requirement of a specific DP for each oligosaccharide to induce the defence response.