Molecular characterization of DNA methyltransferase 1 and its role in temperature change of armyworm Mythimna separata Walker

Abstract

DNA methylation refers to the addition of cytosine residues in a CpG context (5′‐cytosine‐phosphate‐guanine‐3′). As one of the most common mechanisms of epigenetic modification, it plays a crucial role in regulating gene expression and in a diverse range of biological processes across all multicellular organisms. The relationship between temperature and DNA methylation and how it acts on the adaptability of migratory insects remain unknown. In the present work, a 5,496 bp full‐length complementary DNA encoding 1,436 amino acids (named MsDnmt1) was cloned from the devastating migratory pest oriental armyworm, Mythimna separata Walker. The protein shares 36.8–84.4% identity with other insect Dnmt1 isoforms. Spatial and temporal expression analysis revealed that MsDnmt1 was highly expressed in adult stages and head tissue. The changing temperature decreased the expression of MsDnmt1 in both high and low temperature condition. Besides, we found that M. separata exhibited the shortest duration time from the last instar to pupae under 36°C environment when injected with DNA methylation inhibitor. Therefore, our data highlight a potential role for DNA methylation in thermal resistance, which help us to understand the biological role adaptability and colonization of migratory pest in various environments.

DNA Methyltransferases Contribute to Cold Tolerance in Ticks Dermacentor silvarum and Haemaphysalis longicornis (Acari: Ixodidae)

“…In the present study, the first 3 days of cold exposure were marked with a significant decrease in the expression levels of all the Dnmt genes but increased significantly with the prolongation of days of cold treatment. A similar trend was observed in the armyworm (Mythimna separata) where a decreased pattern of expression was observed after short exposures to various temperatures (73). A sharp significant increase in the expression levels of HlDnmt was observed after 9 days of cold exposure (4 • C).…”

“…Due to the vital role of DNA methyltransferases in different biological processes, the knockdown of DsDnmt, DsDnmt1, HlDnmt1, and HlDnmt was carried out to identify their functions by assessing the mortality rate after the exposure of D. silvarum and H. longicornis ticks to sublethal low temperatures of −22 and −14 • C, respectively, for 2 h. Interestingly, the mortality rates of the two tick species significantly increased which underscores the impact of DNA methyltransferases on the cold tolerance of ticks. This result was corroborated by the resultant significant mortality of armyworms (whose MsDnmt1 genes have been knocked down) after exposure to a low temperature (73). Previous studies have demonstrated the effect of extreme temperatures on arthropod development which include reduced fecundity, deformity, and mortality (77)(78)(79).…”

“…To the best of our knowledge, this is the first report of the response of DNA methyltransferases of D. silvarum and H. longicornis ticks to cold stress. Several studies with other species have demonstrated the relationship between DNA methylation, a vital environmentinduced epigenetic phenomenon, and variations in temperature (40,(71)(72)(73). For example, there was a significant change in the expression level of Dnmt3 in the Senegalese sole (fish) after shortterm exposure to embryonic temperatures (42).…”

Cross‐protection interactions in insect pests: Implications for pest management in a changing climate

“…In the northern armyworm (Mythimna separata), inhibition of Dnmt1 via RNAi negatively impacted larval development under elevated temperatures. 103 Comparably, RNAi silencing of Dnmt3 reduced heat and cold tolerance in the white fly (Bemisia tabaci), indicating that de novo methylation is associated with thermal stress responses. 90 Although DNA methylation may drive rapid responses to environmental stress, only a handful of insect studies have explored how DNA methylation is impacted by exposure to single stressors, let alone multiple stressors.…”

“…In de novo methylation, insect DNA methyltransferases appear to respond to temperature stress. In the northern armyworm ( Mythimna separata ), inhibition of Dnmt1 via RNAi negatively impacted larval development under elevated temperatures 103 . Comparably, RNAi silencing of Dnmt3 reduced heat and cold tolerance in the white fly ( Bemisia tabaci ), indicating that de novo methylation is associated with thermal stress responses 90 …”