Molecular cloning and expression of cDNAs encoding alcohol dehydrogenases from Vitis vinifera L. during berry development.

Three full-length cDNAs (VvAdh1, VvAdh2, and VvAdh3) encoding alcohol dehydrogenases (EC 1.1.1.1) were obtained from grape berries (Vitis vinifera L.) by means of PCR and RACE. Pairwise comparisons at the nucleotide level showed that the three cDNAs displayed strong homology in the coding region, but were highly divergent in the 5' and 3' untranslated regions. VvAdh1 and VvAdh2 corresponded to the two previously characterised Adh genes from grapevine, but VvAdh3 was unrelated to known grapevine Adh sequences. The two first cDNAs presented a single ORF of 380 amino acids, whereas the last one has two additional residues. Moreover, the three encoded polypeptides possessed the 22 residues strictly conserved between Adh from different kingdoms. Expression pattern of the individual isogenes was investigated during fruit development. Specific primers were designed, and quantitative RT-PCR experiments were performed to increase the sensitivity of detecting isogenes with a low expression level. Results presented here revealed different developmental regulation of the three Adh isogenes during fruit ripening. VvAdh1 and VvAdh3 transcripts were temporarily accumulated in young, developing berry, whereas VvAdh2 was overexpressed later in fruit development, from the onset of ripening (véraison). Expression analysis also indicated that VvAdh2 accounted for most of the Adh mRNAs present in berries during development. The increased ADH activity detected in berries correlated with the expression pattern of VvAdh2 transcripts. The VvAdh2 and VvAdh3 encoded enzymes were purified from overexpressing E. coli cells. Comparison of kinetic properties of the two ADH enzymes showed a difference in affinity with either ethanol or acetaldehyde as substrates. Significance of multiple Adh expressed in berries is discussed.

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