JXB Advance Access originally published online on May 20, 2008
Journal of Experimental Botany 2008 59(9):2555-2564; doi:10.1093/jxb/ern122
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© 2008 The Author(s).
This is an Open Access article distributed under the terms of the Creative Commons Attribution Non-Commercial License (http://creativecommons.org/licenses/by-nc/2.0/uk/) which permits unrestricted non-commercial use, distribution, and reproduction in any medium, provided the original work is properly cited.
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RESEARCH PAPER |
-Hydroxybutyrate accumulation in Arabidopsis and tobacco plants is a general response to abiotic stress: putative regulation by redox balance and glyoxylate reductase isoforms
Department of Plant Agriculture, University of Guelph, Guelph, Ontario, Canada N1G 2W1
* To whom correspondence should be addressed. E-mail: bshelp{at}uoguelph.ca
Enzymes that reduce the aldehyde chemical grouping (i.e. H-C=O) to its corresponding alcohol are probably crucial in maintaining plant health during stress. Succinic semialdehyde (SSA) is a mitochondrially-generated intermediate in the metabolism of 
-aminobutyrate (GABA), which accumulates in response to a variety of biotic and abiotic stresses. SSA can be reduced to -hydroxybutyrate (GHB) under oxygen deficiency and high light conditions. Recent evidence indicates that distinct cytosolic and plastidial glyoxylate reductase isoforms from Arabidopsis (designated hereinafter as AtGR1 and AtGR2, respectively) catalyse the in vitro conversion of SSA to GHB, as well as glyoxylate to glycolate, via NADPH-dependent reactions. In the present report, the responses of GHB and related amino acids, as well as NADP+ and NADPH, were monitored in leaves from Arabidopsis or tobacco plants subjected to various abiotic stresses (i.e. Arabidopsis during exposure to salinity, drought, submergence, cold, or heat; tobacco during exposure to, and recovery from, submergence). Time-course experiments revealed that GHB accumulated in both Arabidopsis and tobacco plants subjected to stress, and that this accumulation was generally accompanied by higher GABA and alanine levels, higher NADPH/NADP+ ratio, and lower glutamate levels. Furthermore, the analysis of gene expression in Arabidopsis revealed that the relative abundance of GR1 (salinity, drought, submergence, cold, and heat) and GR2 (cold and heat) transcripts was enhanced by the stress tested. Thus, GHB accumulation in plants is a general response to abiotic stress and appears to be regulated by both biochemical and transcriptional processes.
Key words:
Abiotic stress, aldehyde detoxification, -hydroxybutyrate, glyoxylate reductase, redox homeostasis, succinic semialdehyde reductase
Received 7 November 2007; Revised 30 March 2008 Accepted 1 April 2008
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