AUTHOR=Chen Yongcan , Liang Jun , Chen Zhicong , Wang Bo , Si Tong 

TITLE=Genome-Scale Screening and Combinatorial Optimization of Gene Overexpression Targets to Improve Cadmium Tolerance in Saccharomyces cerevisiae

JOURNAL=Frontiers in Microbiology

VOLUME=12

YEAR=2021

URL=https://www.frontiersin.org/journals/microbiology/articles/10.3389/fmicb.2021.662512

DOI=10.3389/fmicb.2021.662512

ISSN=1664-302X

ABSTRACT=<p>Heavy metal contamination is an environmental issue on a global scale. Particularly, cadmium poses substantial threats to crop and human health. <italic>Saccharomyces cerevisiae</italic> is one of the model organisms to study cadmium toxicity and was recently engineered as a cadmium hyperaccumulator. Therefore, it is desirable to overcome the cadmium sensitivity of <italic>S. cerevisiae via</italic> genetic engineering for bioremediation applications. Here we performed genome-scale overexpression screening for gene targets conferring cadmium resistance in CEN.PK2-1c, an industrial <italic>S. cerevisiae</italic> strain. Seven targets were identified, including <italic>CAD1</italic> and <italic>CUP1</italic> that are known to improve cadmium tolerance, as well as <italic>CRS5, NRG1, PPH21, BMH1</italic>, and <italic>QCR6</italic> that are less studied. In the wild-type strain, cadmium exposure activated gene transcription of <italic>CAD1</italic>, <italic>CRS5</italic>, <italic>CUP1</italic>, and <italic>NRG1</italic> and repressed <italic>PPH21</italic>, as revealed by real-time quantitative PCR analyses. Furthermore, yeast strains that contained two overexpression mutations out of the seven gene targets were constructed. Synergistic improvement in cadmium tolerance was observed with episomal co-expression of <italic>CRS5 and CUP1</italic>. In the presence of 200 μM cadmium, the most resistant strain overexpressing both <italic>CAD1</italic> and <italic>NRG1</italic> exhibited a 3.6-fold improvement in biomass accumulation relative to wild type. This work provided a new approach to discover and optimize genetic engineering targets for increasing cadmium resistance in yeast.</p>