Involvement of vacuolar sequestration and active transport in tolerance of Saccharomyces cerevisiae to hop iso-alpha-acids.
The hop plant, Humulus lupulus L., has an exceptionally high content of secondary metabolites, the hop alpha-acids, which possess a range of beneficial properties, including antiseptic action. Studies performed on the mode of action of hop iso-alpha-acids have hitherto been restricted to lactic acid bacteria. The present study investigated molecular mechanisms of hop iso-alpha-acid resistance in the model eukaryote Saccharomyces cerevisiae. Growth inhibition occurred at concentrations of hop iso-alpha-acids that were an order of magnitude higher than those found with hop-tolerant prokaryotes. Chemostat-based transcriptome analysis and phenotype screening of the S. cerevisiae haploid gene deletion collection were used as complementary methods to screen for genes involved in hop iso-alpha-acid detoxification and tolerance. This screening and further analysis of deletion mutants confirmed that yeast tolerance to hop iso-alpha-acids involves three major processes, active proton pumping into the vacuole by the vacuolar-type ATPase to enable vacuolar sequestration of iso-alpha-acids and alteration of cell wall structure and, to a lesser extent, active export of iso-alpha-acids across the plasma membrane. Furthermore, iso-alpha-acids were shown to affect cellular metal homeostasis by acting as strong zinc and iron chelators.
Hazelwood
Lucie A
LA
Department of Biotechnology, Delft University of Technology, Julianalaan 67, 2628 BC Delft, the Netherlands.
Walsh
Michael C
MC
Pronk
Jack T
JT
Daran
Jean-Marc
JM
D000143:Acids / Q000633:toxicity*; D000935:Antifungal Agents / Q000633:toxicity*; D001693:Biological Transport, Active; D017353:Gene Deletion; D020869:Gene Expression Profiling; D005800:Genes, Fungal; D027582:Humulus / Q000737:chemistry*; D010936:Plant Extracts / Q000633:toxicity*; D012441:Saccharomyces cerevisiae / Q000187:drug effects* / Q000235:genetics / Q000254:growth & development / Q000378:metabolism*; D014617:Vacuoles / Q000378:metabolism*
D000143:Acids; D000935:Antifungal Agents; D010936:Plant Extracts