The Species-Specific Acquisition and Diversification of a K1-like Family of Killer Toxins in Budding Yeasts of the Saccharomycotina

Killer toxins are extracellular antifungal proteins that produced by a wide variety of fungi, including Saccharomyces yeasts. Although many killer have been previously identified, their evolutionary origins remain uncertain given these genes mobilized double-stranded RNA (dsRNA) viruses. A survey yeasts from the genus has identified novel toxin with unique spectrum activity paradoxus . The expression this is associated presence dsRNA totivirus and satellite dsRNA. Genetic sequencing confirmed it encodes homology to canonical ionophoric K1 cerevisiae named K1-like (K1L). Genomic homologs K1L were in six non- yeast species Saccharomycotina subphylum, predominantly subtelomeric regions genome. When ectopically expressed S cloned cDNAs, both its can inhibit growth competing species, confirming discovery family biologically active toxins. sporadic distribution supports acquisition horizontal gene transfer followed diversification. phylogenetic relationship between genomic suggests common ancestry flow via dsRNAs DNAs across taxonomic divisions. This appears enable diverse arsenal different for potential use niche competition.