The Metabolism ofcisABA-aldehyde by the Wilty Mutants of Potato, Pea andArabidopsis thaliana

RS-[2H1] cis ABA-aldehyde was fed to ABA-deficient mutants of potato (droopy), pea (wilty) and Arabidopsis thaliana (aba1) along with appropriate non-mutant controls. Both the wilty and aba1 mutants readily oxidized the monodeuterated ABA-aldehyde to ABA. The incorporation of label into ABA by these two mutants was indistinguishable from that detected in the non-mutant controls. In contrast, the droopy mutants poorly incorporated the labelled precursor into ABA. Instead they reduced and isomerized RS-[2H1 ] cis ABA-aldehyde to a mixture of 2, cis and 2, trans ABA-alcohols. Thus the droopy mutant affects the last step in ABA biosynthesis, a position it shares with the tomato mutants, flacca and sitiens. Genetic evidence suggesting that droopy and sitiens may be corresponding gene loci is discussed.