1.9.20
COMPARISON OF mRNA POPULATIONS CODING FOR STILBENE SYNTHASE FROM IN VIITRO GRAPEVINE LEAVES TREATED WITH BIOTIC AND ABIOTIC PHYTOALEXIN INDUCERS

M ADRIAN, A PARIZE, A-C BREUIL, E BOUDON, P JEANDET and R BESSIS

1Laboratoire des Sciences de la Vigne, IUVV, Université de Bourgogne, BP 138, 21004 Dijon, France ; 2INRA, Station de Recherche sur les mycoplasmes, domaine d´Epoisses, BV 1540, 21034 Dijon, France, 3Laboratoire d´Oenologie, Université de Reims, BP 1039, 51687 Reims, France

Background and objectives
Botrytis cinerea is the fungus responsible for grey mould, a disease which can cause serious damage - both qualitative and quantitative - in grapevines. The resistance of grapevines to fungal colonization by Botrytis cinerea appears to be due in part to an induced resistance mechanism involving the rapid production of several stilbenic compounds, namely resveratrol (trans 3,5,4'-trihydroxystilbene) [1-3].

Resveratrol is synthesized by a unique enzyme, stilbene synthase (EC 2.3.1.95), using as substrates malonyl CoA and coumaroyl CoA. One new approach to grapevine disease control involves the potential stimulation of phytoalexin synthesis. The aim of this work is to compare the efficiency of several elicitors of resveratrol synthesis on the accumulation of stilbene synthase mRNAs.

Materials and methods
Leaves from Vitis rupestris cv. Rupestris du Lot clone T110 raised in vitro were collected and elicited for resveratrol synthesis. Elicitors used were either biotic: Botrytis cinerea conidia or abiotic: UV light and aluminum chloride. After elicitation, leaves were incubated for 6 h and frozen in liquid nitrogen. Total RNAs were extracted as described by Tesniere and Vayda [4] and separated by electrophoresis. Stilbene synthase mRNAs were measured by Northen blotting, using a probe provided by H Kindl (University of Marburg, Germany). A kinetic study of stilbene synthase mRNA accumulation in leaves treated by UV light was also carried out using the same method.

Results and conclusions
As previously described using cell suspension cultures of grapevines [5, 6], the transient expression of stilbene synthase mRNAs always shows two maxima (respectively 6 and 24 h after elicitation). The results obtained also indicate a different efficiency of the three elicitors evaluated on the activation of stilbene synthase genes. Genes of stilbene synthase constitute a multigene family. It has been argued [6] that two types of genes contribute to disease resistance (one showing a rapid response and the other a more delayed response ), and it seems likely that different types of genes respond to different elicitors.

References
1. Langcake P, Pryce RJ, 1976. Physiological Plant Pathology 9, 77-86.
2. Sbaghi M, Jeandet P, Faivre B, Bessis R, Fournioux JC, 1995. Euphytica 86, 41-47.
3. Adrian M, Jeandet P, Veneau J, Weston LA, Bessis R, 1997. Journal of Chemical Ecology 23, 1689-1702.
5. Melchior F, Kindl H, 1991. Archives of Biochemistry and Biophysics 288, 552-557.
6. Wiese W, Vornam B, Krause E, Kindl H, 1994. Plant Molecular Biology 26, 667-677.