Abstract
BackgroundDNA methylation, as an essential epigenetic modification found in mammals and plants, has been implicated to play an important role in insect reproduction. However, the functional role and the regulatory mechanism of DNA methylation during insect organ or tissue development are far from being clear.ResultsHere, we found that DNA methylation inhibitor (5-aza-dC) treatment in newly molted pupae decreased the chitin content of pupal wing discs and adult wings and resulted in wing deformity of Bombyx mori. Transcriptome analysis revealed that the up-regulation of chitinase 10 (BmCHT10) gene might be related to the decrease of chitin content induced by 5-aza-dC treatment. Further, the luciferase activity assays demonstrated that DNA methylation suppressed the promoter activity of BmCHT10 by down-regulating the transcription factor, homeobox protein araucan (Bmara). Electrophoretic mobility shift assay, DNA pull-down and chromatin immunoprecipitation demonstrated that Bmara directly bound to the BmCHT10 promoter. Therefore, DNA methylation is involved in keeping the structural integrity of the silkworm wings from unwanted chitin degradation, as a consequence, it promotes the wing development of B. mori.ConclusionsThis study reveals that DNA methylation plays an important role in the wing development of B. mori. Our results support that the indirect transcriptional repression of a chitin degradation-related gene BmCHT10 by DNA methylation is necessary to keep the proper wing development in B. mori.
Highlights
DNA methylation, as an essential epigenetic modification found in mammals and plants, has been implicated to play an important role in insect reproduction
We found that DNA methylation regulates the development of B. mori pupal wing disc by inhibiting the expression of chitinase gene BmCHT10 via transcription factor Bmara in the pupal wing disc, leading to inhibitory effect of chitin degradation in the pupal wing disc
DNA methylation affects wing development and chitin formation In order to investigate whether and how DNA methylation impacts the wing development, we used DNA methylation inhibitor 5-aza-dC to treat B. mori since Bmdnmt1 RNA interference (RNAi) did not work in pupae and 5-aza-dC has been shown to effectively inhibit DNA methylation in B. mori [24]
Summary
DNA methylation, as an essential epigenetic modification found in mammals and plants, has been implicated to play an important role in insect reproduction. The functional role and the regulatory mechanism of DNA methylation during insect organ or tissue development are far from being clear. Some insects do possess the Dnmt1/Dnmt toolkits as in mammals, for example, in Apis mellifera (honey bee), Nasonia vitripennis (parasitoid wasp) and Acyrthosiphon pisum (pea aphid) [19]. Some insects, such as Bombyx mori (silkworm), Tribolium castaneum (red flour beetle) and Pediculus humanus (body louse) only have Dnmt1 [19]. Whether BmDnmt has dual functions of both de novo methylation and maintenance methylation need to be investigated
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