Transcriptomic Analysis of the Cold-Pretreated Larimichthys crocea Showing Enhanced Growth Fitness in Cold Water.

The large yellow croaker Larimichthys crocea is an economically important marine fish species endemic to China and East Asia. Ningde area of Fujian Province is a major L. crocea aquaculture and spawning center in China. L. crocea cultivated at the Zhoushan area appears to be popular but suffered high mortality in cold water during winter seasons. To reduce the mortality rate, we pretreated fish with cold shocks prior to shift to cold water. In this study, we show that cold-pretreated L. crocea 12 days after shift to cold water increase the viability by 5.77-fold compared to the unpretreated (live fish 75 versus 13, p value = 1.775e-06, n = 100). The highest loss of 31 out of 100 fish in the unpretreated group occurred in day 3 after temperature shift. To identify the pretreatment-induced transcriptional changes that may be attributed to cold-resistance and survival, we performed RNA-seq analysis of a total of 48 fish that were prior to and 48 h, 54 h, and 72 h after temperature shift in pretreated and unpretreated groups in sextuplicate. Transcriptomic profiling analysis indicates that pretreatment-induced transcriptional alterations of enzymes involved in FASI, β-oxidation, PUFA synthesis, oxidative phosphorylation, and molecular chaperones persisted after temperature shift, suggesting that these metabolic pathways may play a role in L. crocea cold-resistance and survival. Our study provides insights on how the pretreatment enhances the L. crocea growth fitness in cold water.