Heterologous Expression of Na⁺/H⁺ Antiporter Gene (CvNHA1) from Salt-Tolerant Yeast Candida versatilis in Saccharomyces cerevisiae Na⁺-Transporter Deficient Mutants

Abstract

A Na⁺/H⁺ antiporter gene (CvNHA1) was cloned from the salt-tolerant yeast Candida versatilis. CvNHA1 encodes an antiporter with a typical yeast plasma membrane Na⁺/H⁺ antiporter structure. Transcription of CvNHA1 in C. versatilis cells was dependent on the salinity of the culture. When CvNHA1 was expressed in salt-sensitive Saccharomyces cerevisiae cells, increased salt-tolerance was observed, indicating that Cvnha1p possesses an Na⁺/H⁺ antiporter function, because the increased salt-tolerance was dependent on the extracellular pH. It appears that Cvnha1p mediates only the transport of Na⁺. In an S. cerevisiae transformant harboring a CvNHA1-EGFP fusion plasmid in which the greater part of the C-terminal hydrophilic region of Cvnha1p was deleted by fusion with enhanced green fluorescent protein (EGFP), the Cvnha1-EGFP fusion protein was localized mainly in the plasma membrane, and the NaCl-tolerance of this transformant was greater than that of a strain harboring the entire CvNHA1 gene.