Abstract
Salinity serves as an important environmental factor in ecosystems, driving the evolution of adaptive strategies in euryhaline species. The Pacific white shrimp, Litopenaeus vannamei, is a representative euryhaline species. However, the molecular mechanisms, particularly the roles of cis-regulatory elements, remain elusive in penaeid shrimp. This study tackles this gap by subjecting L. vannamei to a gradual reduction in salinity from 30‱ to 3‱, and then applying ATAC-seq and RNA-seq techniques to dissect the cis-regulation mechanisms underlying low salinity adaptation. A key finding reveals a positive correlation between chromatin accessibility and gene expression, with 36.8% of differentially expressed genes directly associated with changes in chromatin accessibility. The cis-regulation of many osmoregulation-related pathways, such as betaine synthesis and PI3K-Akt signaling pathways, appeared to be a crucial strategy for salinity adaptation in shrimp. By analyzing differentially accessible regions under low salinity stress, we uncovered two known and seven novel candidate transcription factors (TFs) that may play pivotal roles in salinity adaptation. We further conducted a comprehensive analysis of these TFs, including their functions, expression profiles, consensus TFBS motifs, and the functional enrichment and expression profiles of their targeted genes. This study elucidates a complex cis-regulatory network that enables exceptional salinity tolerance in L. vannamei, which provides a foundation for the refinement of genetic breeding programs and desalination aquaculture for penaeid shrimp.