Integrated Analyses of mRNA and microRNA Regulatory Networks at Different Soil Moisture in Tropical Earthworm Eudrilus eugeniae.

Earthworms play crucial roles in soil fertility and are vital to sustainable agriculture and environmental stability. Synchronously, they are highly sensitive to their environment, which limits their abundance and activities. Existing research primarily focuses on their protein-coding gene responses at different chemicals and/or temperature stresses. This study utilized the tropical earthworm Eudrilus eugeniae as a model to investigate how the expression of protein-coding genes and microRNAs are influenced in the anterior tissues at different moisture conditions (30%, 80%, and 100% water-holding capacity). We revealed that molecular chaperones sHsp20, Hsp70, a CHORD-containing protein, and HspBP1-like genes were differentially regulated, and Hsp70 family genes served as hub genes in this process. In addition, a novel lineage-specific microRNA, with an opposite expression trend, was predicted to target three chaperone genes (CHORD-containing protein, Hsp90-like, and Hsp40). Pull-down and dual-luciferase assays further verified their potential interactions. This study suggests holistic cooperation between transcriptional and post-transcriptional mechanisms in the anterior tissues of earthworms facing soil moisture variation and provides new insights into the effect of moisture on the adaptation of biological molecules in earthworms.