Phytoalexins from the Vitaceae: Biosynthesis, Phytoalexin Gene Expression in Transgenic Plants, Antifungal Activity, and Metabolism PHILIPPE JEANDET,* ,² ANNE-CE Ä LINE DOUILLET-BREUIL, ‡ ROGER BESSIS, ‡ SYLVAIN DEBORD, ‡ MOHAMED SBAGHI, § AND MARIELLE ADRIAN ‡ Laboratoire d’Oenologie, URVVC, UPRES EA 2069, Faculte ´ des Sciences, Universite ´ de Reims, B.P. 1039, 51687 Reims Cedex 02, France; Institut Jules Guyot, Universite ´ de Bourgogne, B.P. 27-877, 21078 Dijon Cedex, France; Laboratoire des Biode ´fenses et Substances Naturelles, INRA, Mekne `s, Morocco Resistance of plants to infection by phytopathogenic microorganisms is the result of multiple defense reactions comprising both constitutive and inducible barriers. In grapevine, the most frequently observed and best characterized defense mechanisms are the accumulation of phytoalexins and the synthesis of PR-proteins. Particular attention has been given here to stilbene phytoalexins produced by Vitaceae, specifically, their pathway of biosynthesis (including stilbene phytoalexin gene transfer experiments to other plants) and their biological activity together with fungal metabolism. Keywords: Phytoalexins; resveratrol; Vitaceae; gene transfer; biological activity; metabolism INTRODUCTION Plants in their natural environment are challenged by large numbers of potentially pathogenic microorganisms, mainly fungi, bacteria, and viruses. The factors determining the resistance of plants against phytopathogens belong to a large arsenal of constitutive and inducible (active) defense mecha- nisms (1). The typical preformed, constitutive defenses are the structural barriers (waxes, cutin, suberin, lignin, phenolics, cellulose, callose, and cell-wall proteins) which are often rapidly reinforced upon the infection process. Active defense mecha- nisms mainly involve the oxidative burst, rapid and localized cell death (hypersensitive response), accumulation of phytoal- exins, and synthesis of pathogenesis-related (PR) proteins. Defense response mechanisms are not only activated upon infection by pathogenic microorganisms, but can also be induced by abiotic stresses such as induction with UV-light, or by chemicals (respiratory inhibitors, surfactants, antibiotics, plant regulators, or the salts of heavy metals, as well as elicitors released by the pathogens or products resulting from the activity of fungal degrading-enzymes on host cell-walls) (2). In grapevine, the most frequently observed and best- characterized defense reactions upon fungal infection are accumulation of phytoalexins and the synthesis of PR-proteins (3). Because grapevine is an agriculturally and economically important crop plant, the defense mechanisms of that plant against phytopathogenic microorganisms have attracted con- siderable attention. Among them is the phytoalexin production. Phytoalexins from the Vitaceae have been the subject of numerous studies during the past decade, because these com- pounds are thought to have implications in both phytopathology and human health. As a result, there is a huge increase in the literature dedicated to this particular class of phytoalexins. There have been 238 articles published on resveratrol in the last two years alone compared to 170 during the previous 10 years, with most of these papers concerning the role of resveratrol in human health. Phytoalexins are low-molecular-weight antimicrobial second- ary metabolites of wide interest (2, 4, 5). From a fundamental point of view, studies in phytoalexins provide a large field of investigation for biochemists and plant pathologists, especially concerning the aspects of biosynthesis of these compounds in plants and their metabolism by pathogenic microorganisms. Phytoalexins have been shown to possess biological activity against a wide range of pathogens and can be considered as markers for plant disease resistance. Although most phytoalexins are less phytotoxic than synthetic fungicides, they can accumu- late in large quantities within plant tissues, far exceeding con- centrations necessary to inhibit fungal growth (6). The aspects developed here focus on the biosynthesis and the antifungal activity of grapevine phytoalexins together with their metabolism. Particular attention has also been given to stilbene phytoalexin gene transfer experiments to other plants. PHYTOALEXINS FROM THE VITACEAE Although phytoalexins display an enormous chemical diver- sity (for reviews see 2, 5, 7-9) phytoalexins from the Vitaceae seem to constitute a rather restricted group of molecules belonging to the stilbene family (10), the skeleton of which is based on trans-resveratrol structure (3,5,4′-trihydroxystilbene) (Figure 1). In addition to resveratrol, other compounds con- * Corresponding author. Fax: 333 26 91 33 41. E-mail: philippe.jeandet@ univ-reims.fr. ² Universite ´ de Reims. ‡ Universite ´ de Bourgogne. § INRA. J. Agric. Food Chem. 2002, 50, 2731-2741 2731 10.1021/jf011429s CCC: $22.00 © 2002 American Chemical Society Published on Web 04/11/2002