Journal Article

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

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

in Journal of Experimental Botany

Published on behalf of Society for Experimental Biology

Volume 59, issue 14, pages 3885-3901
Published in print October 2008 | ISSN: 0022-0957
Published online September 2008 | e-ISSN: 1460-2431 | DOI: http://dx.doi.org/10.1093/jxb/ern226

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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 βαβββ 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.

Keywords: At1g07645; Desiccation; Dsi-1VOC; glyoxalase; resurrection plant; vicinal oxygen chelate metalloenzyme; VOC metalloenzyme; Xerophyta

Journal Article.  9495 words.  Illustrated.

Subjects: Plant Sciences and Forestry

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