Abstract
Ammonia nitrogen is a common toxic substance in the aquatic system, which seriously threatens the survival and growth of clams. However, less is known about the ammonia metabolism and detoxification strategy in razor clam. In this study, the polymorphism of the Glutamine synthetase gene from Sinonovacula constricta (Sc-GS) was found to be related to ammonia tolerance. By comparing the coding sequence (CDS) region of Sc-GS from two geographical populations, a total of 14 and 12 single nucleotide polymorphisms (SNPs) were identified, respectively, of which 10 loci were shared between the two populations. Among them, the locus c.1133T > G exhibited an extremely significant and strong association with ammonia tolerance in both populations (P < 0.01), and it was missense mutation, which led to the amino acid change from leucine (Leu) to arginine (Arg). Furthermore, the results about H&E staining and immunohistochemistry of Sc-GS protein in gills and hepatopancreas revealed that it was specifically localized in the lateral cilia of gill filaments and the endothelial cells of hepatocytes. After inhibiting the Sc-GS expression by RNA interference (RNAi) technology, the transcript levels of Sc-GS were extremely significantly downregulated at 24, 48, 72, and 96 h (P < 0.01) in the hepatopancreas. Taken together, these results indicated that the Sc-GS gene may participate in ammonia metabolism. In addition, these results will help to demonstrate the role of Sc-GS in ammonia nitrogen metabolism and provide markers related to ammonia nitrogen tolerance for molecular marker-assisted selection (MAS) of the razor clam.
Highlights
As we all know, the bivalve aquaculture industry is one of the fastest-growing global food sectors, and 89% of bivalves produced all over the world are from aquaculture (FAO, 2020)
The razor clams used in this study were from the Genetic Breeding Research Center of Zhejiang Wanli University, China, and all experimental procedures were approved by the Institutional Animal Care and Use Committee (IACUC) of Zhejiang Wanli University, China
The clams in both populations who survived after 120 h ammonia stress were contemplated as the tolerant group (TG), overall, 130 and 116 surviving clams were collected from ZJ and FJ populations, respectively
Summary
The bivalve aquaculture industry is one of the fastest-growing global food sectors, and 89% of bivalves produced all over the world are from aquaculture (FAO, 2020). Mollusk aquaculture has accounted for 70% (20 million tons) of the total production of aquatic animals (FAO, 2020). Sc-GS Gene Associated With Ammonia-Tolerance ecologically important marine bivalve, with an annual output of 860,265 tons in 2020 (The Ministry of Agriculture and Fishery of the People’s Republic of China, 2021), was mainly polycultured with shrimps, crabs, and fish in Zhejiang and Fujian provinces of China (Li et al, 2015). Under a high-intensive cultivation situation, clams were threatened by various complex contaminants, such as nitrite and ammonia, which were typically important toxicity effectors in aquaculture systems (Cheng et al, 2019). S. constricta, as a benthic bivalve, often lives in mudflats or under 30 ∼ 40 cm of mud in ponds (Frankic and Hershner, 2003), they tend to experience more severe ammonia stress than other aquatic organisms (Zhang et al, 2020). It has been demonstrated that mollusks have a high tolerance to ammonia nitrogen (Widman et al, 2008), there are few reports on their detoxification mechanism of ammonia
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