A Transcriptomic Atlas Underlying Developmental Plasticity of Seasonal Forms of Bicyclus anynana Butterflies

Organisms residing in regions with alternating seasons often develop different phenotypes, or forms, in each season. These forms are often adaptations to each season and result from an altered developmental response to specific environmental cues such as temperature. Although multiple studies have examined form-specific gene expression profiles in a diversity of species, little is known about how environments and developmental transitions, cued by hormone pulses, alter post-transcriptional patterns. In this study, we examine how gene expression, alternative splicing, and miRNA-mediated gene silencing in Bicyclus anynana butterfly hindwing tissue, varies across two rearing temperatures at four developmental timepoints. These timepoints flank two temperature-sensitive periods that coincide with two pulses of the insect hormone 20E. Our results suggest that developmental transitions, coincident with 20E pulses, elicit a greater impact on all these transcriptomic patterns than rearing temperatures per se. More similar transcriptomic patterns are observed pre-20E pulses than those observed post-20E pulses. We also found functionally distinct sets of differentially expressed genes (DEGs) and differentially spliced genes (DSGs) in the seasonal forms. Furthermore, around 10% of DEGs are predicted to be direct targets of, and regulated by, differentially expressed miRNAs (DEmiRs) between the seasonal forms. Many DEGs, DEmiRs, or DSGs potentially regulate eyespot size plasticity, and we validated the differential splicing pattern of one such gene, daughterless. We present a comprehensive and interactive transcriptomic atlas of the hindwing tissue of both seasonal forms of B. anynana throughout development, a model organism of seasonal plasticity.

Automated summary

Organisms in regions with alternating seasons develop different phenotypes in each season, which are adaptations to the environment. This study investigates how gene expression, alternative splicing, and miRNA-mediated gene silencing vary in Bicyclus anynana butterfly hindwing tissue at different developmental timepoints and rearing temperatures. The results suggest that developmental transitions and hormone pulses have a greater impact on transcriptomic patterns than rearing temperatures. The study also identifies differentially expressed genes, differentially spliced genes, and miRNA-regulated genes between the seasonal forms.