CLONING AND MOLECULAR ANALYSIS OF STRUCTURAL GENES INVOLVED IN FLAVONOID AND STILBENE BIOSYNTHESIS IN GRAPE (VITIS-VINIFERA L)

Genes involved in flavonoid and stilbene biosynthesis were isolated fr om grape (Vitis vinifera L.). Clones coding for phenylalanine ammonia- lyase (PAL), chalcone synthase (CHS), chalcone isomerase (CHI), flavan one 3-hydoxylase (F3H), dihydroflavonol 4-reductase (DFR), leucoanthoc yanidin dioxygenase (LDOX) and UDP glucose: flavonoid 3-O-glucosyl tra nsferase (UFGT), were isolated by screening a cDNA library, obtained f rom mRNA from seedlings grown in light for 48 h using snapdragon (Anti rrhinum majus) and maize heterologous probes. A cDNA clone coding for stilbene synthase (StSy) was isolated by probing the library with a sp ecific oligonucleotide. These clones were sequenced and when the putat ive products were compared to the published amino acid sequence for co rresponding enzymes, the percentages of similarity ranged from 65% (UF GT) to 90% (CHS and PAL). The analysis of the genomic organization and expression of these genes in response to light shows that PAL and StS y genes belong to large multigene families, while the others are prese nt in one to four copies per haploid genome. The steady-state level of mRNAs encoded by the flavonoid biosynthetic genes as determined in yo ung seedlings is coordinately induced by light, except for PAL and StS y, which appear to be constitutively expressed.