Terrestrial Zen master: Transcriptomics in long-term aestivation and arousal of Mediterranean earthworms

Earthworms have a crucial role in the maintenance of the biotic and abiotic soil properties, which is important for the biodiversity and productivity of terrestrial ecosystems, especially in the current scenario of climate change. Aestivation is a form of dormancy witnessed in organisms living in deserts or semiarid environments such as the ones found in the central part of the Iberian Peninsula. This work employs next-generation sequencing techniques to explore the changes in gene expression of different aestivation times (1 month and 1 year) as well as changes in gene expression upon arousal. Not surprisingly, the more the aestivation persisted the higher levels of gene downregulation were observed. Conversely, upon arousal, a quick recovery of the levels of gene expression were noted, comparable to the control. Transcriptional changes related to immune responses coming predominantly from abiotic stressors in aestivating earthworms and from biotic stressors in aroused earthworms triggered regulation of the cell fate via apoptosis. Long-term aestivation seemed to be enabled by remodeling of the extracellular matrix, activity of DNA repair mechanisms, and inhibitory neurotransmitters, which could also play a role in lifespan increase. Arousal from 1-month aestivation was on the other hand, characterized by regulation of the cell division cycle. Since aestivation is considered as an unfavorable metabolic state, aroused earthworms probably go through a damage removal process and a subsequent reparation process. This study provides the first transcriptomic investigation done on earthworms in such long aestivation times as well as arousal demonstrating the resilience and adaptability of Carpetania matritensis.