Native and sulfated oligoglucuronans as elicitors of defence-related responses inducing protection against Botrytis cinerea of Vitis vinifera

During the past two decades, β-(1,4)-d-polyglucuronic acids (glucuronans) have been intensively described in literature for their physico-chemical and biological properties in different models. In this study, a bacterial glucuronan partially acetylated was degraded by a fungal glucuronan lyase to obtain unsaturated oligogluguronans, finally tested for their potential as elicitors of natural defences in Vitis vinifera. The objective was to correlate biological activities with specific structural features using oligoglucuronans varying in degree of polymerization, acetylation and sulfation. The results demonstrated that different defence reactions elicited by these anionic oligomers were dependent on degree of polymerization and nature of substituents (acetyl or sulfate groups). Acetylated oligoglucuronans with degrees of polymerization of 10 and 14 induced transient production of H2O2 and expression of some defence-related genes (PAL, STS, Chit4c and PGIP). The infection of grapevine leaves by Botrytis cinerea was reduced (23%) after treatment with acetylated oligoglucuronans having degree of polymerization of 14. Sulfated oligoglucuronans were not effective for production of H2O2 but induced strong expression of other defence-related PIN, PGIP genes. This work opens the way to new and valuable strategies to protect V. vinifera and other plants against pathogens.