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JXB Advance Access published online on September 12, 2008
Journal of Experimental Botany, doi:10.1093/jxb/ern226
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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. This paper is available online free of all access charges (see http://jxb.oxfordjournals.org/open_access.html for further details)

RESEARCH PAPER

Expression of Xhdsi-1VOC, a novel member of the vicinal oxygen chelate (VOC) metalloenzyme superfamily, is up-regulated in leaves and roots during desiccation in the resurrection plant Xerophyta humilis (Bak) Dur and Schinz

I. Mulako, J. M. Farrant, H. Collett and N. Illing*

Department of Molecular and Cell Biology, University of Cape Town, Private Bag, Rondebosch 7701, South Africa

* To whom correspondence should be addressed: E-mail: Nicola.Illing{at}uct.ac.za

The annotation of novel plant genes is frequently based on sequence and structural similarity to known protein motifs. Understanding the biological function of these genes is dependent on identifying conditions under which they are activated, however. The resurrection plant, Xerophyta humilis is a good model system for identifying and characterizing genes which are important for desiccation tolerance. Desiccation induced-1 (dsi-1VOC), a previously uncharacterized plant gene, is up-regulated during desiccation in leaves, roots, and seeds in X. humilis. The X. humilis desiccation induced-1 gene, Xhdsi-1VOC, shares structural homology with the vicinal oxygen chelate (VOC) metalloenzyme superfamily. Proteins in this superfamily share little sequence similarity, but are characterized by a common β{alpha}βββ structural fold. A number of plant orthologues of XhDsi-1VOC have been identified, including Arabidopsis thaliana At1g07645, which is currently annotated as a glyoxalase I-like gene, and many ESTs derived from seed cDNA libraries. Xhdsi-1VOC and its orthologues do not, however, contain the glutathione and zinc binding sites conserved in glyoxalase I genes. Furthermore, expression of Xhdsi-1VOC in yeast failed to rescue a yeast glyoxalase I mutant. Messenger RNA transcripts for At1g07645 accumulate during seed maturation, but are not induced by water loss, salt or mannitol stress in vegetative tissue in Arabidopsis. It is concluded that dsi-1VOC is a seed-specific gene in desiccation-sensitive plants that is activated by water loss in vegetative tissues in the resurrection plant X. humilis and plays an important role in allowing plant tissues to survive loss of 95% of their relative water content.

Key words: At1g07645, Desiccation, Dsi-1VOC, glyoxalase, resurrection plant, vicinal oxygen chelate metalloenzyme, VOC metalloenzyme, Xerophyta

Received 25 July 2008; Accepted 11 August 2008


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