DNA methylation dynamics associated with seasonal wing plasticity of Bicyclus anynana butterflies

Over the years, multiple studies have linked phenotypic plasticity to changes in gene expression and alternative splicing, but the role of epigenomic regulation, such as DNA methylation, in mediating plastic responses are still poorly understood. DNA methylation has been proposed as a promising regulatory mechanism because of its potential effects on transcriptional activity and pre-mRNA splicing, especially when present within gene bodies in insects. Here, we examined the role of DNA methylation in the developing wings of the Bicyclus anynana butterflies by testing its association with differential gene expression and alternative splicing between the two seasonal forms. Methylation differences between the seasonal forms were largely enriched in housekeeping genes but were not present in transcription factors and developmental genes associated with wing or eyespot development, or in components of the ecdysone signalling pathway. We found a copy of DNA methyltransferase (Dnmt1) expressed faintly across the whole wing, with no specific expression in eyespots or other specific wing patterns in either seasonal form. Overall, our study provides a comprehensive characterization of the DNA methylation in wing development in two seasonal forms, while providing very little support for the role of DNA methylation in driving differences in transcriptional profiles of two seasonal wing forms and in wing metamorphosis.