A stress-inducible gene for 9-cis-epoxycarotenoid dioxygenase involved in abscisic acid biosynthesis under water stress in drought-tolerant cowpea.
Four cDNA clones named CPRD (cowpea responsive to dehydration) corresponding to genes that are responsive to dehydration were isolated using differential screening of a cDNA library prepared from 10-h dehydrated drought-tolerant cowpea (Vigna unguiculata) plants. One of the cDNA clones has a homology to 9-cis-epoxycarotenoid dioxygenase (named VuNCED1), which is supposed to be involved in abscisic acid (ABA) biosynthesis. The GST (glutathione S-transferase)-fused protein indicates a 9-cis-epoxycarotenoid dioxygenase activity, which catalyzes the cleavage of 9-cis-epoxycarotenoid. The N-terminal region of the VuNCED1 protein directed the fused sGFP (synthetic green-fluorescent protein) into the plastids of the protoplasts, indicating that the N-terminal sequence acts as a transit peptide. Both the accumulation of ABA and expression of VuNCED1 were strongly induced by drought stress in the 8-d-old cowpea plant, whereas drought stress did not trigger the expression of VuABA1 (accession no. AB030295) gene that encodes zeaxanthin epoxidase. These results indicate that the VuNCED1 cDNA encodes a 9-cis-epoxycarotenoid dioxygenase and that its product has a key role in the synthesis of ABA under drought stress.
Iuchi
S
S
Laboratory of Plant Molecular Biology, RIKEN Isukuba Institute, Tsukuba, Ibaraki, Japan.
Kobayashi
M
M
Yamaguchi-Shinozaki
K
K
Shinozaki
K
K
D000040:Abscisic Acid / Q000096:biosynthesis*; D000595:Amino Acid Sequence; D017360:Arabidopsis / Q000235:genetics; D015152:Blotting, Northern; D015139:Blotting, Southern; D018076:DNA, Complementary; D049308:Dioxygenases; D007887:Fabaceae / Q000201:enzymology / Q000235:genetics* / Q000378:metabolism; D015971:Gene Expression Regulation, Enzymologic; D018506:Gene Expression Regulation, Plant; D014975:Lutein / Q000378:metabolism; D008969:Molecular Sequence Data; D010088:Oxidoreductases / Q000378:metabolism; D010105:Oxygenases / Q000737:chemistry / Q000235:genetics*; D010940:Plant Proteins; D010946:Plants, Medicinal; D017386:Sequence Homology, Amino Acid; D014867:Water
D018076:DNA, Complementary; D010940:Plant Proteins; D014867:Water; D000040:Abscisic Acid; D010088:Oxidoreductases; C097153:zeaxanthin epoxidase; D010105:Oxygenases; D049308:Dioxygenases; C109043:9-cis-epoxy-carotenoid dioxygenase; D014975:Lutein