Expression of the Oenococcus oeni trxA gene is induced by hydrogen peroxide and heat shock

Sequencing of the DNA region located upstream of the alpha-acetolactate syn thase and decarboxylase (alsS-alsD) cluster of Oenococcus oeni allowed iden tification of an ORF, named trxA. This encodes a protein of 104 amino acids very similar to known thioredoxins. The protein encoded by the cloned frag ment was able to complement Escherichia coli strains lacking a functional t hioredoxin. Considering the results of protein sequence comparisons and com plementation experiments, it was concluded that the trxA gene encodes a fun ctional thioredoxin. Studies of trxA expression showed that the abundance o f trxA mRNA was similar during all growth stages. A significant increase in trxA mRNA levels was observed in the presence of hydrogen peroxide in the medium or after heat shock. A single transcriptional start site was determi ned with total RNA isolated from cells subjected or not subjected to oxidat ive stress or heat shock. In each case the same promoter region was identif ied and shown to have a high similarity to the consensus promoter sequence of Gram-positive bacteria, as well as to that of E. coli and the previously mapped promoters from O. oeni.