MOLECULAR-IDENTIFICATION OF ZEAXANTHIN EPOXIDASE OF NICOTIANA-PLUMBAGINIFOLIA, A GENE INVOLVED IN ABSCISIC-ACID BIOSYNTHESIS AND CORRESPONDING TO THE ABA LOCUS OF ARABIDOPSIS-THALIANA
E. Marin et al., MOLECULAR-IDENTIFICATION OF ZEAXANTHIN EPOXIDASE OF NICOTIANA-PLUMBAGINIFOLIA, A GENE INVOLVED IN ABSCISIC-ACID BIOSYNTHESIS AND CORRESPONDING TO THE ABA LOCUS OF ARABIDOPSIS-THALIANA, EMBO journal, 15(10), 1996, pp. 2331-2342
Abscisic acid (ABA) is a plant hormone which plays an important role i
n seed development and dormancy and in plant response to environmental
stresses. An ABA-deficient mutant of Nicotiana plumbaginifolia, aba2,
was isolated by transposon tagging using the maize Activator transpos
on. The aba2 mutant exhibits precocious seed germination and a severe
wilty phenotype, The mutant is impaired in the first step of the ABA b
iosynthesis pathway, the zeaxanthin epoxidation reaction, ABA2 cDNA is
able to complement N.plumbaginifolia aba2 and Arabidopsis thaliana ab
a mutations indicating that these mutants are homologous. ABA2 cDNA en
codes a chloroplast-imported protein of 72.5 kDa, sharing similarities
with different mono-oxigenases and oxidases of bacterial origin and h
aving an ADP-binding fold and an FAD-binding domain, ABA2 protein, pro
duced in Escherichia coil, exhibits in vitro zeaxanthin epoxidase acti
vity. This is the first report of the isolation of a gene of the ABA b
iosynthetic pathway, The molecular identification of ABA2 opens the po
ssibility to study the regulation of ABA biosynthesis and its cellular
location.