Putative 3-nitrotyrosine detoxifying genes identified in the yeast Debaryomyces hansenii: In silico search of regulatory sequences responsive to salt and nitrogen stress

Abstract

Background: During saline stress, the yeast Debaryomyces hansenii has as a strategy to avoid the oxidation of proteins the synthesis of tyrosine, which reacts with nitrogen radicals to form 3-nitrotyrosine, these contributes to the high halotolerace of the yeast, because it prevents the effects of associated oxidative stress. However, it has not been determined how does D. hansenii counteract the presence of this toxic compound. In this work we evaluated the D. hansenii capacity to assimilate 3-nitrotyrosine as a unique nitrogen source, and measured its denitrase activity under NaCl stress. In order 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 promoter had binding 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, evaluated by RT-PCR, showed a high expression in sodium and nitrogen stress.

Conclusions: D. hansenii can grow in presence of 3-nitrotyrosine as the only nitrogen source, and have a high especific denitrase activity to degradate 3-nitrotyrosine in 1 and 2 M NaCl stress conditions. The results suggest that given the lack of information for transcriptional factors in D. hansenii, genes identified by our in silico analysis may help to explain 3-nitrotyrosine assimilation mechanisms.