Regulation and Manipulation of the Biosynthesis of Abscisic Acid, Including the Supply of Xanthophyll Precursors |
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Authors: | Ian B Taylor Tineke Sonneveld Timothy D H Bugg Andrew J Thompson |
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Institution: | (1) Plant Sciences Division, School of Biosciences, The University of Nottingham, Sutton Bonington Campus, Loughborough, Leicestershire, LE12 5RD, UK;(2) Department of Chemistry, University of Warwick, Gibbet Hill Road, Coventry, CV4 7AL, UK;(3) Warwick HRI, University of Warwick, Wellesbourne, Warwick, CV35 9EF, UK |
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Abstract: | Mutant plants deficient in the phytohormone abscisic acid (ABA) are typically unable to control their stomatal behavior appropriately
in response to water stress, leading to a “wilty” phenotype. In plant species showing strong seed dormancy, ABA deficiency
of the seed results in a second clearly recognizable phenotype, that is, early germination. Mutants selected by means of this
latter character are often collectively termed “viviparous.” These two broad classes include mutants that are defective in
their ability to synthesize ABA. A number of these genetic lesions have been assigned to specific steps in ABA biosynthesis
and have been invaluable in elucidating many important features of the pathway. Most of the genes encoding ABA biosynthetic
enzymes have now been cloned and their expression has been studied and manipulated. Genetically modified plants constitutively
overexpressing ABA biosynthesis genes have been produced and analyzed over the last 6 years. In some cases these plants have
been found to have elevated ABA concentrations, leading to altered stomatal behavior and increased seed dormancy. Genetic
manipulation of ABA synthesis in photosynthetic tissues has been most effectively achieved through overexpression of the key
rate-limiting biosynthetic enzyme 9-cis-epoxycarotenoid dioxygenase, and downregulation of the major catabolic enzyme ABA 8′-hydroxylase. However in non-photosynthetic
tissue manipulation of ABA synthesis is a more complex task because of the limiting supply of xanthophyll precursors. The
recent cloning of genes encoding enzymes controlling important pathways of ABA catabolism has been reviewed elsewhere, and
so only information relevant to the regulation and manipulation of ABA synthesis, including supply of xanthophyll precursors,
is discussed in this review. |
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Keywords: | ABA synthesis Regulation Genetic manipulation Water-use efficiency Seed dormancy |
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