GSE136991
A white to opaque like phenotypic switch in the yeast Torulaspora microellipsoides
Torulaspora microellipsoides is a unicellular budding yeast of the Saccharomycetaceae family and is primarily associated with viticulture, however it has not been studied with regards to growth morphology or phenotypic switching. We discovered that T. microellipsoides undergoes a low-frequency morphological switch from small budding haploid (white) yeast to larger, higher ploidy (opaque) yeast. Genome sequencing of both cell types did not reveal any conspicuous differences, but comparison of transcriptomes by mRNA-seq revealed 511 differentially regulated genes, with white cells having greater expression of genes involved in stress resistance and complex carbohydrate utilization, and opaque cells up-regulating genes involved in ribosome biogenesis. Growth experiments showed that white cells are in general physiologically more resistant to stationary phase conditions and oxidative stress than opaque cells, but the latter performed better under some conditions and are more tolerant to cold temperatures. Opaque cells are also phenotypically more unstable than white cells and give rise to derivatives with diverse phenotypes and different total DNA content.  We propose that ability of T. microellipsoides to switch phenotype is an ecological adaptation to specific niches, as has been suggested for similar morphological switching phenomena in distantly related species such as C. albicans, and suggest switching of this nature may be a more a more broadly utilized biological strategy among yeasts than previously thought. Overall design: DNA or RNA was extracted from triplicate matched log-phase samples of each cell type (verified to the pure by plating and microscopy), extracted using standard methods, and sequencing libraries prepared using standard methods.