XVI International Botanical Congess

The abscisic acid (ABA) biosynthetic pathway involves the formation of a 9-cis-epoxy-carotenoid precursor.Oxidative cleavage then results in the formation of xanthoxin, which is subsequently converted to ABA.A number of steps in the pathway may control of ABA synthesis, but particular attention has been given to the enzyme involved in the oxidative cleavage reaction i.e. 9-cis-epoxy-carotenoid dioxygenase (NCED). Cloning of a gene encoding this enzyme in maize was first reported by Schwartz et al,1997 (Science 276:1872-1874). Mapping and DNA sequencing studies indicated that a wilty tomato mutant was due to a deletion in the gene encoding an enzyme with a very similar amino acid sequence to this maize NCED (Burbidge et al,1999,The Plant Journal,17:426-431). The potential use of this gene in altering ABA content will be discussed.