Characterization of a salt-induced <it>DhAHP</it>, a gene coding for alkyl hydroperoxide reductase, from the extremely halophilic yeast <it>Debaryomyces hansenii</it>

• Main Authors: Ku Maurice SB, Yen Yung-fu, Chao Hsiu-fung
• Format: Article
• Language: English
• Published: BMC 2009-08-01
• Series: BMC Microbiology
• Online Access: http://www.biomedcentral.com/1471-2180/9/182

<p>Abstract</p> <p>Background</p> <p><it>Debaryomyces hansenii </it>is one of the most salt tolerant species of yeast and has become a model organism for the study of tolerance mechanisms against salinity. The goal of this study was to identify key upregulated genes that are involved in its adaptation to high salinity.</p> <p>Results</p> <p>By using forward subtractive hybridization we have cloned and sequenced <it>DhAHP </it>from <it>D. hansenii </it>that is significantly upregulated during salinity stress. <it>DhAHP </it>is orthologous to the alkly hydroperoxide reductase of the peroxiredoxin gene family, which catalyzes the reduction of peroxides at the expense of thiol compounds. The full-lengthed cDNA of <it>DhAHP </it>has 674 bp of nucleotide and contains a 516 bp open reading frame (ORF) encoding a deduced protein of 172 amino acid residues (18.3 kDa). <it>D. hansenii </it>Ahp is a cytosolic protein that belongs to the Ahp of the 1-Cys type peroxiredoxins. Phylogentically, the <it>Dh</it>Ahp and <it>Candida albicans </it>Ahp11 (Swiss-Prot: <ext-link ext-link-id="Q5AF44" ext-link-type="sprot">Q5AF44</ext-link>) share a common ancestry but show divergent evolution. Silence of its expression in <it>D. hansenii </it>by RNAi resulted in decreased tolerance to salt whereas overexpression of <it>DhAHP </it>in <it>D. hansenii </it>and the salt-sensitive yeasts <it>Saccharomyces cereviasiae </it>and <it>Pichia methanolica </it>conferred a higher tolerance with a reduced level of reactive oxygen species.</p> <p>Conclusion</p> <p>In conclusion, for the first time our study has identified alkly hydroperoxide reductase as a key protein involved in the salt tolerance of the extremely halophilic <it>D. hansenii</it>. Apparently, this enzyme plays a multi-functional role in the yeast's adaptation to salinity; it serves as a peroxidase in scavenging reactive oxygen species, as a molecular chaperone in protecting essential proteins from denaturation, and as a redox sensor in regulating H₂O₂-mediated cell defense signaling.</p>