Comparative transcriptome analyses provide insights into the adaptation mechanisms to acute salt stresses in juvenile Sinonovacula constricta

Sinonovacula constricta is an economically important bivalve species in China, Korea and Japan. It widely resides in estuarine and coastal areas where salinity fluctuates rapidly. However, little is known about its adaptation mechanisms to acute salt stresses. To address this, we establish nine cDNA libraries (triplicate each treatment) from juvenile S. constricta, which were subjected to low salinity (5 psu), optimal salinity (15 psu, the control) and high salinity (25 psu) for 6 h, respectively. Illumina sequencing generated 478,587,310 clean reads totally, which were assembled into 427,057 transcripts of 246,672 unigenes. Compared with the control, 1259 and 2163 differentially expressed genes (DEGs) were identified under acute low and high salt stresses, respectively. GO and KEGG enrichment analyses of DEGs suggested that several key metabolic modulations were mainly responsible for the acute salt stresses. Based on the significantly highlighted KEGG pathways, some key DEGs were identified and discussed in details, including cysteine sulfinic acid decarboxylase, alanine transaminase, glutamine synthetase, glutamate dehydrogenase, nitric-oxide synthase, arginase, betaine-homocysteine S-methyltransferase, serine racemase, L-serine ammonia-lyase, phosphoserine phosphatase, glutamate 5-kinase, glutamate-5-semialdehyde dehydrogenase, ornithine-oxo-acid transaminase, ornithine decarboxylase, stearoyl-CoA desaturase, carnitine O-palmitoyltransferase 1, serine/threonine-protein kinase, NF-kappa-B, NF-kappa-B inhibitor alpha, phosphoenolpyruvate carboxykinase and carbohydrate response element binding protein. Furthermore, some potential osmolytes were speculated. In summary, this study would not only provide insights into the adaptation mechanisms to acute salt stresses in juvenile S. constricta, but also facilitate to better understand the physical and biochemical performances of this bivalve species involved in acute salt stresses. Moreover, the transcriptome data obtained here greatly enriched the genetic information of S. constricta, which would be valuable for promoting its molecular biology researches. Juvenile S. constricta were first subjected to low salinity (5 psu), optimal salinity (15 psu, the control) and high salinity (25 psu) for 6 h respectively. Subsequently, samples in whole organism were used to establish 9 cDNA libraries (triplicate each group) by Illumina sequencing.