Functional characterization of heavy metal transporters of the mycorrhizal fungus Suillus luteus

Abstract

Since the Industrial Revolution, human activities have led to an enormous rise of heavy metal concentrations in certain areas. Heavy metals are toxic for living organisms, even in minor concentrations. Some organisms, however, developed specific survival strategies. Some of these strategies are mediated by the Ycf1 and Yor1 ATP binding cassette (ABC)-transporters. In the yeast Saccharomyces cerevisiae, the Ycf1 transporter is involved in vacuolar sequestration, the Yor1 in efflux of heavy metal ions.

The research topics in this master thesis are the identification of homologues of these two transporters in the ectomycorrhizal fungus Suillus luteus, and the investigation if these homologues also have a role in heavy metal tolerance, more specifically in cadmium tolerance. By means of a phylogenetic analysis, with the aid of bioinformatic tools like NCBI, JGI and MEGA6, the evolutionary relationship was shown. The Ycf1 gene was isolated from S. luteus and introduced into a Ycf1 deletion yeast strain. This strain was subjected to a complementation test by drop assay, wherein it was cultivated on media containing a gradient of cadmium concentrations.

The phylogenetic analysis has shown that S.luteus and all Boletales fungi in this study have one homologue of Ycf1 and at least one homologue of Yor1. The complementation test indicated that the expression of SlYcf1 might rescue the yeast mutants in media with high cadmium concentrations, but further detailed analysis is required to confirm the function of the SlYcf1 gene.