06/A269
Estudio de fitoalexinas terpénicas involucradas en los mecanismos de resistencia a Phaeocremonium parasiticum, hongo asociado a la enfermedad hoja de malvón de vid (Vitis vinifera L.)
Study the role of terpene fitoalexins involved in resistance mechanicism in the responses of grape plants, Vitis vinifera L. to fungal attack, Phaeocremonium parasiticum (responsible for the “hoja de malvón” dissease)
Director: PICCOLI, Patricia
E-mail: ppiccoli@fca.uncu.edu.ar
Co-Director: GATICA, Marta
Integrantes: MARTINEZ, Liliana; PONCE, María Teresa; SILVA, María Fernanda; GARCÍA L., Sandra; ECORIAZA, Georgina; CÉSARI, Cecilia; COHEN, Ana; MORENO, Daniela; PIZZI, Martín; BUSTAMANTE, Carlos; BOTTINI, Rubén
Resumen Técnico
El objetivo general del tema a estudiar se centra en responder a la pregunta de si existe una relación causal entre el ataque de Phaeocremonium parasiticum, hongo asociado a la enfermedad “hoja de malvón” en vid (Vitis vinifera L.), y la producción de fitoalexinas terpénicas como respuesta de defensa por parte de los tejidos de la planta. Para ello se caracterizarán los compuestos de interés biocida por GC-MS, se estudiarán su metabolismo con precursores radioactivos e isótopos pesados, así como el control de las enzimas responsables de regular su producción mediante las variaciones en la expresión de genes relacionados con la respuesta de defensa de la vid al ataque del hongo. La finalidad es aportar al conocimiento de los mecanismos de defensa involucrados que ayuden en la búsqueda de vides más resistentes a la enfermedad. En síntesis, nuestra contribución se centrará en aclarar algunos aspectos de la interacción vid-hongo, partiendo de la hipótesis de que las fitoalexinas terpénicas actúan como factores de defensa de la planta ante P. parasiticum como agente patógeno. Si bien varios hongos se asocian con esta enfermedad, nos centraremos en P. parasiticum, ya que éste se aisló e identificó en Argentina (Gatica et al. 2000, 2001, 2004), y es el de mayor presencia en correlación con los síntomas de la enfermedad (Gatica 2004)
Summary
The culture of grapes (viticulture) is the main fruit crop industry in the world based on its economic importance (Coombe 1989). It constitutes the principal source of income in the Province of Mendoza, Argentina, along with the actual winemaking industry (ca. 70 % of the grape and wine produced in Argentina, Censo Vitícola 2001). In the last three decades, the winemaking industry has experienced a continuous expansion worldwide. This increase has occurred both in magnitude as well as in quality of the final product. Both the viticulture and winemaking businesses offer great opportunities for small and mid-size investors, since wine price relies both on quality, but also (and substantially) in scarcity (Zraly 2000). It is well known that wine excellence is greatly dependent of grape quality, the latter being highly affected either negatively or positively by abiotic (water availability, UV-B radiation, Dry et al. 2000a, b and c) and biotic (fungal diseases, Gatica et al. 2000). Terpenes are a vast class of compounds that include several important plant biomolecules like phytoalexins (substances the plant cell produces to protect itself from pest attacks, Croteau et al. 2000) and phytohormones noticeably likes ABA, Brassinosteroids and GAS(Crozier et al. 2000)Among the most relevant biotic stresses that affect grapes is the so called “hoja de malvón” disease, caused by a complex of fungi from which the most prominent is Phaeoacremonium parasiticum (Gatica et al. 2000 and 2004). This disease has been described only in Argentina and its incidence has been growing in last years (Gatica et al. 2001 and 2004), thus it is important to know the way grape plants can resist the attack. Theoretically phytoalexins are a vast group of diverse molecules (generally terpenes) showing antimicrobial activity (Croteau et al. 2000). They are not usually present in healthy plants and their synthesis is elicited by fungal attack (Lamb et al. 1989, Dixon and Lamb 1990). However, there are no references in the scientific literature relating terpene cyclases, enzymes responsible for synthesis of terpenic phytoalexin, with grape plant defense. Terpene cyclases are key enzymes in the biosynthetic route of terpenes, including hormones (ABA, gibberellins, brasinosteroides, pigments, membrane structural sterols and phytoalexins involved in the plant defense. Pioneering work of Chappell and Nable (1987) showed accumulation of a terpenic phytoalexin, capsidiol, in cell suspension cultures of Nicotiana tabacum exposed to fungal elicitors. The fungal elicitors induced the de novo synthesis of terpene cyclases while esqualene synthase activity (responsible for the synthesis of structural sterols) decreased (Vogeli and Chappell 1988 and 1990, Devarenne et al. 1998). To chemically characterize the compounds responsible for wine flavor and biocide activity towards the fungi causative of the “hoja de malvón” disease, check the hypothesis that terpenic phytoalexin participate in the grape response towards P. parasiticum