Saccharomyces paradoxus K66 Killer System Evidences Expanded Assortment of Helper and Satellite Viruses

Area of Science:

• Virology
• Yeast Genetics
• Molecular Biology

Background:

• The Saccharomycetaceae yeast family is increasingly recognized for its diverse dsRNA viruses.
• Understanding the cross-dependence of these viruses is crucial for their study.

Purpose of the Study:

• To isolate and characterize dsRNA viruses from a Saccharomyces paradoxus killer strain.
• To investigate the K66 toxin's function, receptors, and genetic modulators.
• To demonstrate the cohabitation of multiple virus types within a single yeast strain.

Main Methods:

• Isolation and whole-genome sequencing of dsRNA viruses from Saccharomyces paradoxus AML-15-66.
• Sequence analysis and comparison with known yeast viruses.
• Functional analysis of the K66 toxin, including cell binding assays.
• Genetic screening using Saccharomyces cerevisiae deletion library.

Main Results:

• Identification of helper and satellite viruses within the Totiviridae family in S. paradoxus AML-15-66.
• Sequencing revealed SpV-LA-66 and SpV-M66, with distinct similarities to known viruses.
• K66 toxin showed significant differences from K28 toxin, with structural similarities to K1/K2 toxins.
• 125 gene products were identified as important for K66 toxin function, with 85% shared with K1/K2 toxins.
• Beta-1,6-glucans were identified as primary receptors for the S. paradoxus K66 toxin.
• Demonstration of cohabitation of different helper and satellite virus types in a wild-type S. paradoxus strain.

Conclusions:

• The study provides the first evidence of cohabiting helper and satellite viruses in wild-type S. paradoxus.
• Beta-1,6-glucans are confirmed as key receptors for the S. paradoxus K66 toxin.
• The findings deepen the understanding of dsRNA virus diversity and interactions within the Saccharomycetaceae family.