Evaluation of cold tolerance and gene expression patterns associated with low-temperature stress in giant freshwater prawn Macrobrachium rosenbergii

Abstract

The giant freshwater prawn (GFP) Macrobrachium rosenbergii is a commercially important cultured species that originates from tropical and subtropical regions and has poor cold tolerance. This study investigated the species’ cold tolerance and regulation patterns of the related response genes, using GFP juveniles subjected to extreme low-temperature treatment. The water temperature was decreased from 26 °C at a rate of approximately 1 °C every 4 h until all prawns died. The temperatures resulting in lowest LT50 (lethal temperature at which 50% prawn die) and lowest lethal temperature were approximately 12.5 °C and 11.5 °C, respectively. Phenotypic traits and hardness of the exoskeleton generally had little effect on the cold tolerance of the prawns; however, two body-weight groups showed a highly significant difference (P < 0.01) in cold-tolerance ability, with smaller prawns (≤2 g) more susceptible to low temperatures than larger ones. Furthermore, the cold-tolerant group (last 10% of mortalities) had better cold tolerance than the cold-sensitive group (first 10% of mortalities). Additionally, comparative transcriptomic analysis was performed for the cold-tolerant and cold-sensitive groups under low-temperature stress, and for the control group maintained at ~26 °C. Through the identification of differentially expressed genes (DEGs) and RT-qPCR validation experiments, several key candidate genes were screened out, including acetyl-CoA carboxylase and laccase1-like protein, which may exert considerable influence on the response of GFP to low-temperature stress. More DEGs were found in hepatopancreas than in muscle, and several key pathways were significantly enriched in hepatopancreas, including folate biosynthesis, starch and sucrose metabolism, and pancreatic secretion, indicating the hepatopancreas plays a critical role in cold tolerance. Within the pathway of folate biosynthesis, the key upregulated gene is Alkaline phosphatase, suggesting that this gene is critical in response to low temperatures. The present results contribute to understanding the molecular mechanism of cold tolerance in this species.