Membrane-bound pyrophosphatase of human gut microbe Clostridium methylpentosum confers improved salt tolerance in Escherichia coli, Saccharomyces cerevisiae and tobacco.

Membrane-bound pyrophosphatases (PPases) are involved in the adaption of organisms to stress conditions, which was substantiated by numerous plant transgenic studies with H(+)-PPase yet devoid of any correlated evidences for other two subfamilies, Na(+)-PPase and Na(+),H(+)-PPase. Herein, we demonstrate the gene cloning and functional evaluation of the membrane-bound PPase (CmPP) of the human gut microbe Clostridium methylpentosum. The CmPP gene encodes a single polypeptide of 699 amino acids that was predicted as a multi-spanning membrane and K(+)-dependent Na(+),H(+)-PPase. Heterologous expression of CmPP could significantly enhance the salt tolerance of both Escherichia coli and Saccharomyces cerevisiae, and this effect in yeast could be fortified by N-terminal addition of a vacuole-targeting signal peptide from the H(+)-PPase of Trypanosoma cruzi. Furthermore, introduction of CmPP could remarkably improve the salt tolerance of tobacco, implying its potential use in constructing salt-resistant transgenic crops. Consequently, the possible mechanisms of CmPP to underlie salt tolerance are discussed.