Transcriptome profiling reveals differential gene expression associated with changes in the morphology and stress tolerance of the biocontrol yeast, Pichia cecembensis

A considerable amount of research is being conducted on the utilization of antagonistic yeasts for the biological control of pre- and postharvest fungal diseases of horticultural crops. Previously, we found an increase in the stress tolerance and biocontrol efficacy of two biofilm-forming yeasts, Pichia kudriavzevii and Candida diversa, associated with the transition from a yeast-like to pseudohyphal morphology. In the present study, the biocontrol yeast, Pichia cecembensis was also found to exhibit a yeast-like or pseudohyphal morphology when grown on yeast peptone dextrose (YPD) with either 2% or 0.3% agar, respectively. The pseudohyphal form exhibited greater tolerance to heat, oxidative (H2O2), and salt (NaCl) stresses than the yeast-like form. Moreover, the biocontrol efficacy of P. cecembensis against blue mold (Penicillium expansum) on apple fruit increased markedly from the yeast-like form to the pseudohyphal form. A transcriptomic analysis of the two forms was conducted utilizing RNA-seq. A total of 20,991,425 and 25,009,573 clean reads, were obtained from the cDNA libraries constructed from the yeast-like and pseudohyphal forms of P. cecembensis, respectively. Over 3000 differentially expressed genes (DEGs) were identified between the pseudohyphal and yeast-like forms, with 2490 DEGs being up-regulated, and 843 DEGs being down-regulated. The identified DEGs were associated with metabolism, development, signaling, membrane transport, and stress response. In order to verify the results of the RNA-seq data, RT-qPCR was conducted on a subset of 24 genes. The present study provides new information on the physiology and genetic regulation of biocontrol yeasts that exhibit dual growth forms.