MicroRNA transcriptomics in liver of the freeze‐tolerant gray tree frog (Dryophytes versicolor) indicates suppression of energy‐expensive pathways.

The rapid and reversible nature of microRNA (miRNA) transcriptional regulation is ideal for implementing global changes to cellular processes and metabolism, a necessary asset for the freeze‐tolerant gray tree frog (Dryophytes versicolor). D. versicolor can freeze up to 42% of its total body water during the winter and then thaw completely upon more favorable conditions of spring. Herein, we examined the freeze‐specific miRNA responses in the gray tree frog using RBiomirGS, a bioinformatic tool designed for the analysis of miRNA‐seq transcriptomics in non‐genome sequenced organisms. We identified 11 miRNAs differentially regulated during freezing (miR‐140‐3p, miR‐181a‐5p, miR‐206‐3p, miR‐451a, miR‐19a‐3p, miR‐101‐3p, miR‐30e‐5p, miR‐142‐3p and ‐5p, miR‐21‐5p, and miR‐34a‐5p). Gene Ontology and Kyoto Encyclopedia of Genes and Genomes pathway enrichment analysis suggests these miRNAs play roles in downregulating signaling pathways, apoptosis, and nuclear processes while enhancing ribosomal biogenesis. Overall, these findings point towards miRNA inducing a state of energy conservation by downregulating energy‐expensive pathways, while ribosomal biogenesis may lead to prioritization of critical processes for freeze‐tolerance survival. Significance Statement: Animals capable of undergoing metabolic rate depression are valuable models for advancing our understanding of how core metabolic pathways and physiological processes are regulated. This has key implications for medical research including organ transplants, inducing states of "suspended animation," and increasing survival windows for traumatic injury. Growing evidence implicates microRNA (miRNA) regulation of central metabolic pathways as a crucial mechanism for inducing the changes necessary for entrance into, and maintenance of, a metabolically‐depressed state. This study predicted mRNA targets and biological processes that change during freezing in D. versicolor liver, allowing future studies to investigate this potentially critical subset of miRNAs and their roles, which will help elucidate the molecular underpinnings of surviving this extreme environmental stress. [ABSTRACT FROM AUTHOR]