Abstract
BackgroundAccurate regulation of tissue- and stage-specific expression of genes is prerequisite for normal development in organisms. DNA methylation plays an important role in modulating gene expression in mammals and plants. However, there is no direct evidence showing how DNA methylation regulates gene transcription in insects.ResultsDuring the development of Bombyx mori wing, the expression level of DNA methyltransferase 1 (BmDnmt1) gradually declined and became stationary at pupal stage, resulting in a lower methylation rate of the intragenic promoter of the mid-pupal wing-specific gene BmCHSA-2b, an epidermal chitin synthase controlling mid-pupal wing development in B. mori. The higher methylation rate of the promoter in the pupal epidermis was decreased and BmCHSA-2b transcription was significantly increased by the treatment with the DNA methylation inhibitor, 5-azacytidine-2′-deoxycytidine, suggesting that DNA methylation regulates the tissue-specific expression of BmCHSA-2b. Pupa-specific transcription factor BmDEAF1 bound to the unmethylated intragenic promoter and activated the BmCHSA-2b transcription in the mid-pupal wing. BmDnmt1 and BmDeaf1 influenced the BmCHSA-2b transcription by binding competitively to the CpG island in the promoter.ConclusionsAll the data together demonstrate that the cooperation between the down-regulation of BmDnmt1 and increased stage-specific expression of BmDeaf1 enhances BmCHSA-2b tissue- and stage-specific transcription to ensure mid-wing development in B. mori. This study highlights an elaborate regulation mechanism how tissue- and stage-specific gene expression is regulated through promoter methylation in insect development.
Highlights
Accurate regulation of tissue- and stage-specific expression of genes is prerequisite for normal development in organisms
We revealed that demethylation or unmethylation of CpG island 2 (CpGI2) of the intragenic promoter, as a consequence of DNA methyltransferase 1 (DNMT1) down-regulation, enhanced the binding of pupa-specific transcription factor BmDeaf1 to the unmethylated CpGI2 and activated B. mori chitin synthase (BmCHSA)-2b transcription in mid-pupal wing, demonstrating that intragenic promoter methylation plays an important role in mediating tissue and stagespecific expression of genes in insects
The results showed that the BmDnmt1 protein bound to the CpGI2 fragment (Fig. 2d, lane 2)
Summary
Accurate regulation of tissue- and stage-specific expression of genes is prerequisite for normal development in organisms. DNA methylation plays an important role in modulating gene expression in mammals and plants. There is no direct evidence showing how DNA methylation regulates gene transcription in insects. DNA methylation has been studied extensively in mammals and plants [3]. The study of DNA methylation is rudimentary, compared to that in mammals and plants. It is observed that DNA methylation in the gene promoter of the invertebrate, Ciona intestinalis, was tissue- and/or cell-type specific [18], similar to those identified in mammals. In Drosophila S2 cells, up-regulated promoter methylation rate inhibited the promoter activity of steroidogenic enzyme [19], suggesting the regulatory functionality of DNA methylation in the promoter of insect. The direct experimental evidence for the regulatory mechanism of DNA methylation has not been reported in insects
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
