Abstract
Adaptation of insects to different altitudes remain largely unknown, especially those endemic to the Tibetan Plateau (TP). Here, we generated the transcriptomes of Gynaephora menyuanensis and G. alpherakii, inhabiting different high altitudes on the TP, and used these and the previously available transcriptomic and genomic sequences from low-altitude insects to explore potential genetic basis for divergent high-altitude adaptation in Gynaephora. An analysis of 5,869 orthologous genes among Gynaephora and other three low-altitude insects uncovered that fast-evolving genes and positively selected genes (PSGs) in the two Gynaephora species were enriched in energy metabolism and hypoxia response categories (e.g. mitochondrion, oxidation-reduction process, and response to oxidative stress). Particularly, mTOR signaling pathway involving hypoxia was enriched by PSGs, indicating this well-known pathway in mammal hypoxia adaptation may be an important signaling system in Gynaephora. Furthermore, some PSGs were associated with response to hypoxia (e.g. cytochrome proteins), cold (e.g. dehydrogenase) and DNA repair (e.g. DNA repair proteins). Interestingly, several insect-specific genes that were associated with exoskeleton and cuticle development (e.g. chitinase and ecdysteroids) had experienced positive selection, suggesting the specific adaptive mechanisms in insects. This study is favourable for understanding the adaptive evolution of Gynaephora and even TP insects to divergent altitudes.
Highlights
The speciation of animals is closely related to different environmental conditions[1,2], and ecologically divergent selection is an essential evolutionary force in ecological speciation[1,3]
Studies of the mechanisms of divergent altitude adaptation have been conducted in different animals using the RNA sequencing (RNA-seq) technology[28,30]
We explored how Gynaephora commonly adapt to the Tibetan Plateau (TP) environments in the long-term evolutionary process by functional enrichment analysis for fast-evolving genes (FEGs) and positively selected genes (PSGs) sets in the ancestral branch of the two Gynaephora species
Summary
One gene encoded proteins related to single-organism metabolic (cytochrome b5, CYTB5); two genes encoded proteins associated with oxidation-reduction process (gamma-glutamyl phosphate reductase, GPR; probable saccharopine dehydrogenase [NADP(+), L-glutamate-forming], SDH); two genes encoded proteins involved in obsolete ATP catabolic process (protein scarlet, ST; ABC transporter F family member 4, ABCF4); gene encoding 3-hydroxyacyl-CoA dehydrogenase type-2 protein (SCU) participated in many biological function, including acyl-CoA metabolic process, oxidation-reduction process, and fatty acid metabolic process; the remaining two genes encoding DNA repair protein, rad[50] (RAD50) and DNA repair protein xrcc (XRCC) were annotated to DNA repair and response to hypoxia, respectively. Three genes associated with hypoxia, cold and UV radiation were annotated to GO terms involving cellular response to DNA damage stimulus (double-strand break repair protein, MRE11), obsolete ATP catabolic process (protein scarlet, ST), and oxidation-reduction process (gamma-glutamyl phosphate reductase, GPR). Four significantly enriched GO terms (three and one terms belonged to biological process and molecular function, respectively) were obtained, including “metabolic process” and “acid phosphatase activity”
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