Comparative Analysis of Stress Adaptation in the Yeast Microbiome of Cactus

Together with other fungi, yeasts make up a significant component of the plant microbiome. As the planet warms, cacti expand their range. Cactus-associated yeasts are known to exhibit signatures of adaptation to the cactus host. Our previous isolation of a wild Saccharomyces paradoxus yeast from a cactus in a forest of oaks populated by S. cerevisiae prompted us to further explore cactus-associated fungi and look for genomic and phenotypic signatures of adaptation. Here we characterize seven yeast isolates, five from cacti and two from adjacent non-cactus plants, among which was a novel species of Coniochaeta isolated from wild grape that we name C. udwismasis. Closely-related isolates from distinct plant hosts exhibited distinct features, including differences in thermotolerance, freeze-thaw tolerance, pigmentation, and predicted septin protein complex assembly, providing new insights into possible mechanisms of cactus adaptation by the yeast microbiome.