Abstract
The increasing sea temperature caused by global warming has resulted in severe mortalities in maricultural scallops. Therefore, improving thermal tolerance has become an active research area in the scallop farming industry. Bay scallop (Argopecten irradians irradians) was introduced into China in 1982 and has developed into a vast aquaculture industry in northern China. To date, genetic studies on thermal tolerance in bay scallops are limited, and no systematic screening of thermal tolerance-related loci or genes has been conducted in this species. In the present study, we conducted a genome-wide association study (GWAS) for thermal tolerance using the Arrhenius break temperature (ABT) indicators of 435 bay scallops and 38,011 single nucleotide polymorphism (SNP) markers. The GWAS identified 1,906 significant thermal tolerance-associated SNPs located in 16 chromosomes of bay scallop. Gene ontology and Kyoto Encyclopedia of Genes and Genomes pathway analyses showed that 638 genes were enriched in 42 GO terms, while 549 annotated genes were enriched in aggregation pathways. Additionally, the SNP (15-5091-20379557-1) with the lowest P value was located in the transcriptional coactivator p15 (PC4) gene, which is involved in regulating DNA damage repair and stabilizing genome functions. Further analysis in another population identified two new thermal tolerance-associated SNPs in the first coding sequence of PC4 in bay scallops (AiPC4). Moreover, AiPC4 expression levels were significantly correlated (r = 0.675–0.962; P < 0.05) with the ABT values of the examined bay scallops. Our data suggest that AiPC4 might be a positive regulator of thermal tolerance and a potential candidate gene for molecular breeding in bay scallop aiming at thermal tolerance improvement.
Highlights
Aquatic products constitute an important source of food consumed all over the world
Some candidate gene families that are closely associated with thermal tolerance in scallops have been identified by homology alignment in other studies, such as GRP94 (94 kDa glucose-regulated protein) (Wang et al, 2018a), TNFR (Xing et al, 2016b), HSP70 (Yang et al, 2014), and metallothionein 1 (Yang et al, 2013)
Four and six single nucleotide polymorphism (SNP) in the promoter region of HSP70 and HSP90 were identified to be associated with heat tolerance of two bay scallop populations, via elevating transcriptional activities of target genes (Yang et al, 2014, 2015)
Summary
Aquatic products constitute an important source of food consumed all over the world. As of 2019, global aquaculture output was 80.1 million tons (46.8 million tons contributed by China), generating an estimated 238.0 billion dollars (139.1 billion dollars by China) in revenue (FAO, 2019). Many bivalves are economically important aquaculture species that account for approximately 22.8% of the aquatic products market worldwide (Moffitt and Cajas-Cano, 2014). A continuous increase in the production of bivalves has been observed in recent years (Steeves et al, 2018), several obstacles (e.g., environmental stress, biotic and abiotic factors) hamper the development of the industry. Anoxia tolerance (Zwaan et al, 1995; Chen et al, 2007a), salinity tolerance (Chen and Chen, 2000; Roldan-Carrillo et al, 2005), and tolerance to bacterial pathogens (Richards et al, 2015; Rojas et al, 2016) are closely related to mortality in bivalves, which may have adverse effect on global aquaculture production. Researchers gave more attention on the tolerance ability of aquatic commercial bivalves for sustainable development of shellfish industry
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