Cloning and characterization of the abscisic acid-specific glucosyltransferase gene from adzuki bean seedlings.
The glycosylated forms of abscisic acid (ABA) have been identified from many plant species and are known to be the forms of ABA-catabolism, although their (physiological) roles have not yet been elucidated. ABA-glucosyltransferase (-GTase) is thought to play a key role in the glycosylation of ABA. We isolated an ABA-inducible GTase gene from UDP-GTase homologs obtained from adzuki bean (Vigna angularis) seedlings. The deduced amino acid sequence (accession no. AB065190) showed 30% to 44% identity with the known UDP-GTase homologs. The recombinant protein with a glutathione S-transferase-tag was expressed in Escherichia coli and showed enzymatic activity in an ABA-specific manner. The enzymatic activity was detected over a wide pH range from 5.0 to 9.0, the optimum range being between pH 6.0 and 7.3, in a citrate and Tris-HCl buffer. The product from racemic ABA and UDP-D-glucose was identified to be ABA-GE by gas chromatography/mass spectrometry. The recombinant GTase (rAOG) converted 2-trans-(+)-ABA better than (+)-S-ABA and (-)-R-ABA. Although trans-cinnamic acid was slightly converted to its conjugate by the GTase, (-)-PA was not at all. The mRNA level was increased by ABA application or by water stress and wounding. We suggest that the gene encodes an ABA-specific GTase and that its expression is regulated by environmental stress.
Xu
Zheng-Jun
ZJ
Bio-oriented Technology Research Advancement Institution, Tokyo 105-0001, Japan.
Nakajima
Masatoshi
M
Suzuki
Yoshihito
Y
Yamaguchi
Isomaro
I
D000040:Abscisic Acid / Q000378:metabolism* / Q000494:pharmacology; D000595:Amino Acid Sequence; D001483:Base Sequence; D015152:Blotting, Northern; D015139:Blotting, Southern; D003001:Cloning, Molecular; D018076:DNA, Complementary / Q000737:chemistry / Q000235:genetics; D004926:Escherichia coli / Q000235:genetics; D007887:Fabaceae / Q000187:drug effects / Q000201:enzymology / Q000235:genetics*; D015971:Gene Expression Regulation, Enzymologic / Q000187:drug effects; D018506:Gene Expression Regulation, Plant / Q000187:drug effects; D005964:Glucosyltransferases / Q000235:genetics* / Q000378:metabolism; D006863:Hydrogen-Ion Concentration; D018546:Hypocotyl / Q000201:enzymology; D008969:Molecular Sequence Data; D010937:Plant Growth Regulators / Q000378:metabolism* / Q000494:pharmacology; D011993:Recombinant Fusion Proteins / Q000235:genetics / Q000378:metabolism; D017422:Sequence Analysis, DNA; D013379:Substrate Specificity; D014316:Tritium; D014532:Uridine Diphosphate Glucose / Q000494:pharmacology
D018076:DNA, Complementary; D010937:Plant Growth Regulators; D011993:Recombinant Fusion Proteins; D014316:Tritium; D000040:Abscisic Acid; D005964:Glucosyltransferases; D014532:Uridine Diphosphate Glucose