Screening method for cDNAs encoding putative enzymes converting loganin into secologanin by a transgenic yeast culture

A screening method was developed for the detection of enzymes converting lo ganin to secologanin, a precursor in the biosynthesis of indole alkaloids. The method uses a transgenic yeast culture expressing two cDNAs encoding en zymes involved in the terpenoid indole alkaloid biosynthesis. In the presen ce of secologanin, the yeast culture produces a yellow compound visible on nitrocellulose. This color change was used to screen a cDNA library of Cath aranthus roseus for a putative enzyme converting loganin into secologanin.