A glucosyltransferase (GT) of Arabidopsis, UGT71B6, recognizing the naturally occurring enantiomer of abscisic acid (ABA) in vitro, has been used to disturb ABA homeostasis in planta. Transgenic plants constitutively overexpressing UGT71B6 (71B6‐OE) have
been analysed for changes in ABA and the related ABA metabolites abscisic acid glucose ester (ABA‐GE), phaseic acid (PA), dihydrophaseic acid (DPA), 7′‐hydroxyABA and neo‐phaseic acid. Overexpression of the GT led to massive accumulation of ABA‐GE and reduced
levels of the oxidative metabolites PA and DPA, but had marginal effect on levels of free ABA. The control of ABA homeostasis, as reflected in levels of the different metabolites, differed in the 71B6‐OEs whether the plants were grown under standard conditions or subjected to wilt stress.
The impact of increased glucosylation of ABA on ABA‐related phenotypes has also been assessed. Increased glucosylation of ABA led to phenotypic changes in post‐germinative growth. The use of two structural analogues of ABA, known to have biological activity but to differ in their
capacity to act as substrates for 71B6 in vitro, confirmed that the phenotypic changes arose specifically from the increased glucosylation caused by overexpression of 71B6. The phenotype and profile of ABA and related metabolites in a knockout line of 71B6, relative to
wild type, has been assessed during Arabidopsis development and following stress treatments. The lack of major changes in these parameters is discussed in the context of functional redundancy of the multigene family of GTs in Arabidopsis.
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Document Type: Research Article
CNAP, Department of Biology (Area 8), University of York, York YO10 5YW, UK, and
Plant Biotechnology Institute, National Research Council of Canada, 110 Gymnasium Place, Saskatoon, Saskatchewan, Canada S7N 0W9
May 1, 2006