The Pea Gene NA Encodes ent-Kaurenoic Acid Oxidase 1

Abstract

The gibberellin (GA)-deficient dwarf na mutant in pea tPisum sativum) has severely reduced internode elongation, reduced root growth, and decreased leaflet size. However, the seeds develop normally. Two genes, PsKAOl and PsKA02, encoding cytochrome P450 monooxygenases of the subfamily CYP88A were isolated. Both PsKAOl and PsKA02 had cllt-kaurenoic acid oxidase (KAO) activity, catalyzing the three steps of the GA biosynthetic 'pathway from ellt-kaurenoic acid to GA12 when expressed in yeast (Saccharolllyces cereuisiaes. In addition to the intermediates cnt-7n-hydroxykaurenoic acid and GAn-aldehyde, some additional products of the pea KAO activity wen! detected, induding ent-60',70'-dihydroxykaurenoic acid and 7(:l-hydroxykaurenolide. The NA gene encodes PsKA01, because in two independent mutant alleles, na-t and na-L, PsKAOl had altered sequences and the five-base deletion in PsKAOl associated with the tl17-1 allele cosegregated with the dwarf 1117 phenotype. P5KAOI was expressed in the stem, apical bud, leaf, pod, and root, organs in which GA levels have previously been shown to be reduced in IIIl plants. PsKA02 was expressed only in seeds and this may explain the normal seed development and normal GA biosynthesis in seeds of lla plants.