Study On DNA Methylated Fragments Related To The Wing Dimorphism Of Brown Planthopper

Brown planthopper Nilaparvata lugens is one of the most important rice pests, which distributs in Asia widely. It has phenomenon of wing dimorphism during adult stage. Macropterous adults have ability to migrate and avoid bad environment. Brachypterous adults are gregarious and progenitive which can be good for the increase of the population. At present, most researches on wing dimorphism are focusing on physiological, biochemical and ecological levels, while less study is carried out from epigenetic level. The differentially methylated fragments between macropterous and brachypterous female adults of N. lugens were detected by the methylation-sensitive representational difference analysis(MS-RDA), and then some of these fragments were chosed to analyze the methylation level and patterns during each developmental stage by bisulfite sequencing method. The results were as the followings:(1) 53 fragments were screened from macropterous and brachypterous female adults using MS-RDA, 26 of them came from macropterous female adults and others from the brachypterous female adults. 26 fragments(>200bp) have got the Genebank number. Based on blast analysis, there were 6 fragments homologous with 18 S ribosomal genes and 11 fragments homologous with the EST sequence from N. lugens. Among 36 fragments with no homologous information, seven fragments had similar structures with repetitive sequences and 11 fragments might contained a potential promoter region.(2) Comparaing these fragments with the brown planthopper genome database(obtained from Zhejiang University), three of them were found to be homologous with histone H15, V-type ATP synthase subunit I and Prohormone-3 respectively. These three fragments and the fragment homologous with 18 Sribosomal gene were analyzed by bisulfite sequencing to understand their methylation levelsand patterns during the progess of development. The results showed that methylation at the site of CpT was the main type in the fragment homologous with H15 gene, CpA DNA methylation was the main types in the fragment homologous with the Prohormone-3 gene, while CpG DNA methylation in the fragment homologous with the V-type ATP synthase subunit I or 18 S ribosomal gene was mainly form. The variation of DNA methylation level of cytosine residues in nymphal stage was obvious(range: 9.89%~12.96%). There were different trends in the level of CpG dinucleotide methylation for the 4 analyzed fragments during nymphal stage. The methylation level of fragments from 18 s ribosomal gene was over 48%, even over 70% during adult stage. The methylated levels for other fragments were below 25%.In this study, 53 differentially methylated DNA fragments associated with long or short wing types were obtained, and found thatmethylatedpatterns andlevels of cytosine residues for the measured fragments during different developmental stages were different and changeable. The results will conducive tounderstand the molecular mechanism of insect wing polymorphism from the perspective of epigenetic, at the same time, it will help to develop a new way to control the pests as well.