Transcriptome analyses provide the first insight into the molecular basis of cold tolerance in Larimichthys polyactis.

Larimichthys polyactis is one of the most economically important marine fish species that have become newly cultured in China in recent years. The gene expression changes that L. polyactis experiences in cold toleranceis still unknown, limiting the expansion of its cultivation, fast growth, and high yield. To investigate the molecular mechanism behind L. polyactis's cold tolerance and to provide a resource for conducting genetic research on L. polyactis, transcriptome sequencing using RNA-seq was performed on individuals that survived cold stress at 4 °C (cold tolerant, CT), and individuals that barely survived 4 °C (cold sensitive, CS), which was considered as the control. A number of 387,607,550 clean reads were obtained from the transcriptomes, and comparative transcriptomic analysis identified 141 differently expressed genes (DEGs), of which 67 were up-regulated and 74 were down-regulated in CT compared to CS under cold stress. Furthermore, ten differently expressed genes were selected from the RNA-Seq analysis to be further validated by real-time PCR. Functional network analysis indicated that L. polyactis adapted to cold stress by employing a series of mechanisms to minimize damages caused by exposure to cold temperatures. The molecular mechanisms identified through RNA-Seq included Extracellular matrix (ECM) receptor interaction, glycerolipid metabolism, regulation of autophagy and focal adhesion pathway as playing vital roles in cold tolerance in L. polyactis. This study may help elucidate how L. polyactis tolerates cold, which is of value for breeding cold-tolerant L. polyactis stocks for cultivation.