Antibody preparation, gene expression and subcellular localization of L-idonate dehydrogenase in grape berry.

L-Idonate dehydrogenase (L-IdnDH) is the only known enzyme of the tartaric acid (TA) biosynthetic pathway in grape berries. Previous studies on this enzyme only focused on the transcriptional expression of this gene. Here, the antibody against L-IdnDH was prepared by cloning the full-length cDNAs of VvIdnDH from grape berries, highly expressing fusion protein in Escherichia coli cells, and then immunizing rabbits. Expression of VvIdnDH at the transcriptional and translational levels in grape berries increased within 3 weeks after full bloom and then decreased, similarly to the trend for TA contents. Almost no VvIdnDH transcript was detected in the mature berries, but VvIdnDH protein was detectable. In the 21-d berries, this enzyme was largely located in the cytoplasm and a few in the cell wall, secondary cell wall, and chloroplast, whereas in the 60 berries, it was distributed mainly in the vacuole and cytoplasm.