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Putative 3-nitrotyrosine detoxifying genes identified in the yeast Debaryomyces hansenii : In silico search of regulatory sequences responsive to salt and nitrogen stress
Castro, Daniela E.; Murguía-Romero, Miguel; Thomé, Patricia E.; Peña, Antonio & Calderón-Torres, Marissa
Abstract
Background: During salt stress, the yeast Debaryomyces hansenii synthesizes tyrosine as a strategy to avoid the
oxidation of proteins. Tyrosine reacts with nitrogen radicals to form 3-nitrotyrosine. 3-nitrotyrosine prevents
the effects of associated oxidative stress and thus contributes to the high halotolerace of the yeast. However,
the mechanism of how D. hansenii counteracts the presence of this toxic compound is unclear. In this work, we
evaluated D. hansenii's capacity to assimilate 3-nitrotyrosine as a unique nitrogen source and measured its
denitrase activity under salt stress. To identify putative genes related to the assimilation of 3-nitrotyrosine, we
performed an in silico search in the promoter regions of D. hansenii genome.
Results: We identified 15 genes whose promoters had binding site sequences for transcriptional factors of
sodium, nitrogen, and oxidative stress with oxidoreductase and monooxygenase GO annotations. Two of these
genes, DEHA2E24178g and DEHA2C00286g, coding for putative denitrases and having GATA sequences, were
evaluated by RT-PCR and showed high expression under salt and nitrogen stress.
Conclusions: D. hansenii can grow in the presence of 3-nitrotyrosine as the only nitrogen source and has a high
specific denitrase activity to degrade 3-nitrotyrosine in 1 and 2 M NaCl stress conditions. The results suggest
that given the lack of information on transcriptional factors in D. hansenii, the genes identified in our in silico
analysis may help explain 3-nitrotyrosine assimilation mechanisms.
Keywords
Extremophiles; Free tyrosine; Halotolerance; Irreversible damages; Neutralization of free radicals; Nitrogen source; Osmoregulatory mechanisms; Oxidative stress; Salt-tolerant yeast; Transcriptional factors (TF); Tyrosine synthesis
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