Longevity and transposon defence, the case of termite queens
Sensory and Behavioural Biology
Final Report Abstract
Social insects are emerging model organisms of ageing research. The queens of termites, ants, bees, and wasps can have extraordinary lifespans of up to several decades, while their related nestmate workers are generally short-lived. In a former project, we had identified transposable elements (TEs) as a potential cause of caste-specific ageing in the termite Macrotermes bellicosus. In this species, queens can live for more than 20 years, while workers have a lifespan of a few months only. Associated with these lifespan differences, we had found that old workers are characterized by a high activity of TEs and a downregulation of genes from a TE defence pathway. In old queens TEs were inactive, in line with a constant upregulation of this defence pathway. TEs are ‘jumping genes’ that can replicate independently within genome and have been associated with ageing in a broad range of organisms. In the current project, we wanted to investigate this system in more detail. We generated a high-quality genome assembly for M. bellicosus using PacBio HiFi (high fidelity) sequencing. Detailed analyses comparing transcriptomes of heads and fat bodies showed a strong tissue effect of age-related gene- and TE-expression in workers. However, several transcribed genes as well as specific TEs were consistently associated with age in both tissues and across colonies. These TEs can be used as ageing markers in follow-up studies. Furthermore, the generation and analyses of new genome assemblies for three additional termite species showed species- and lineage-specific TE-patterns that reflected the termites’ species phylogeny. Deducing CpG methylation patterns from the kinetics of PacBio sequencing also revealed species- and lineage-specific TE methylation patterns. This together with a negative correlation between the abundance of different TE types and their methylation level suggests that TE methylation suppresses TE activity. This contrasts with results for holometabolous insects, like fruit flies or social Hymenoptera. However, our results are in line with recent evidence that outside holometabolous insects, TE methylation can be common in arthropods. Our results will guide future studies to investigate the interplay between ageing, TE activity and its defence mechanisms.
Publications
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Arms races between selfish genetic elements and their host defence. Cold Spring Harbor Laboratory.
Qiu, Bitao; Elsner, Daniel & Korb, Judith
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Epigenetic regulation and division of labor in social insects. Current Opinion in Insect Science, 58, 101051.
Okwaro, Louis A. & Korb, Judith
