Transcriptome Analysis of Pacific White Shrimp (Litopenaeus vannamei) Under Prolonged High-Salinity Stress

The Pacific white shrimp(Litopenaeus vannamei)is a marine species commonly farmed worldwide.In northern China,it has been increasingly cultured in high-salinity waters(>40),but exhibits poor growth performance.In this study,postlarval shrimps were acclimated to salinity 55,cultivated for 3 months at this salinity,and compared with a control group reared at general salinity 25.Subsequently,high-throughput RNA sequencing was applied to compare the transcriptomic responses in the gills and hepatopancreas of the shrimps in the control group and the treatment group,while the weights of the shrimps in these two groups were significantly different.The results revealed that 11834 and 2115 genes were significantly differentially expressed in the gills and hepatopancreas,respectively.Additionally,enrichment analysis of the differentially expressed genes indicated that osmoregula-tion-associated Gene Ontology terms and KEGG pathways were similar between the two subgroups of the shrimp maintained at high salinity,suggesting that the growth rate of shrimp at high salinity is independent of osmoregulation.Furthermore,examination of the shrimp with different growth rates(i.e.,weights)at high salinity revealed molt-associated processes,namely,increased expression of ecdysone response genes and downstream effector genes in the gills and hepatopancreas of slow-growing shrimp,suggesting a role of the molt-associated processes in the regulation of shrimp growth at high salinity.Thus,we not only report adaptive transcriptomic responses of L.vannamei to prolonged high-salinity stress,but also provide new insights into the shrimp growth regulation at high salinity.