In grapevine (Vitis vinifera L.), defense responses after microbial infection or treatment with elicitors involve accumulation of phytoalexins, oxidative burst, and the synthesis of pathogenesis-related proteins. Oligosaccharide fractions from fungal or algal cell walls efficiently induce the defense responses, but a detailed analysis of the elicitor-plant cell surface interaction at the molecular level is precluded by the lack of chemically pure oligosaccharide elicitors. A grapevine liquid cell culture system was used to examine the properties of cyclodextrins (CDs) as inducers of defense responses. This work shows that the chemically pure heptakis(2,6-di-O-methyl)-betaCD caused a dramatic extracellular accumulation of the phytoalexin resveratrol and changes in peroxidase activity and isoenzymatic pattern. Other modified CDs tested on several grapevine cell lines resulted in different eliciting capacities of CDs and different sensibilities of the cell lines. The spent medium of elicited cultures was shown to disturb Botrytis cinerea growth in a plate assay.

Tobacco mosaic virus (TMV) is a widespread plant virus from the genus Tobamovirus that affects tobacco and tomato plants causing a pathology characterised by cell breakage and disorganisation in plant leaves and fruits. In this study we undertook a proteomic approach to investigate the molecular and biochemical mechanisms potentially involved in tomato fruit defence against the viral infection. The comparison of 2-D gels from control and TMV-infected but asymptomatic tomato fruits revealed changes in several proteins. The differential expression of peptidases, endoglucanase, chitinase and proteins participating in the ascorbate-glutathione cycle in infected fruits suggests that pathogenesis-related proteins and antioxidant enzymes may play a role in the protection against TMV infection. TMV coat protein appeared as a prominent spot in 2-D gels from TMV-infected asymptomatic fruits. A Triton X-114 phase-partitioning step of tomato protein extracts favoured the solubilisation of TMV coat protein and the enrichment of two aminopeptidases not present in control fruits. PMF and MS/MS data of the 2-D gel-isolated TMV coat protein is proposed as a powerful analysis method for the simultaneous tobamovirus detection, species determination and strain differentiation in virus-infected fruit commodities.

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