Impacts of seasonality on gene expression in the Chinese Horseshoe Bat

Seasonality can cause changes in many environmental factors which
potentially affects gene expression. Here, we used a bat species
(Rhinolophus sinicus) from eastern China as a model to explore the
molecular mechanisms of seasonal effects, in particular during
phenological shifts in the spring and autumn. Based on the analysis of 45
RNA-seq samples, we found strong seasonal effects on gene expression, with
a large number of genes identified as either specific or biased to each
season. Weighted gene co-expression network analysis also identified
multiple modules significantly associated with each season. These seasonal
genes were further enriched into different functional categories.
Consistent with effects of phenological shifts on bats, we found that
genes related to promoting food intake were highly expressed in both
autumn and spring. In addition, immunity genes were also highly expressed
in both seasons although this seasonal immune response had tissue
specificity in different seasons. In female bats, genes related to the
delay of ovulation (e.g. NPPC, natriuretic peptide precursor type C) were
highly expressed in October, while genes associated with the promotion of
reproduction (e.g. DIO2, iodothyronine deiodinase 2) were biasedly
expressed in April. Lastly, we found multiple known core clock genes in
both October-biased and April-biased expressed genes, which may be
involved in regulating the start and end of hibernation, respectively.
Overall, together with studies in other land and aquatic animals, our work
supports that seasonal gene expression variations may be a general
evolutionary response to environmental changes in wild animals.