Abstract
Taurine has been reported high amounts in marine animals to maintain osmotic balance between osmoformers and sea water. Approximately 80% of the total amino-acid content is taurine in Pacific oyster Crassostrea gigas, an intertidal and euryhaline species. In this study, we cloned the two copies of cysteine sulfinate decarboxylase (CSAD), the key enzyme in taurine biosynthesis pathway, screened in oyster genome data. Sequentially, we compared the expression patterns of CgCSAD1 and CgCSAD2 under low salinity treatment (8‰ and 15‰) using different families from two populations. There was no correlation between the expression of CSAD and the different population. Notably, CgCSAD1 increased significantly in treated groups for 24 h, but CgCSAD2 had no significant differentiation. Moreover, the results of CgCSAD1 interference provided the evidence of the positive correlation between CgCSAD1 expressions and taurine contents. The zinc finger domain showed in multi-alignment results may be the important character of CgCSAD1 as the key enzyme in taurine biosynthesis to regulate taurine pool in response to low salinity. This study provides a new evidence for the important role of taurine in adaptation to low salinity in oyster. In addition, it is a good model to discuss the function and evolution of the duplication in mollusks.
Highlights
Environmental factors, especially salinity, in intertidal zones fluctuated acutely owing to tides, rainfall, surface runoff and so on
Two copies of cysteine sulfinate decarboxylase (CSAD) were cloned in C. gigas and were named as CgCSAD1 and CgCSAD2
The CgCSAD1 cDNA was 2,097 bp in length and contained a 60 bp 5′-untranslated region (UTR), a 369 bp 3′-UTR, and a 1,668 bp open reading frame (ORF). It encodes a predicted polypeptide consisting of 555 amino acid residues and an estimated molecular mass of 63.35 kDa; The CgCSAD2 cDNA was 1,713 bp in length and included a 82 bp 5′-UTR, a 146 bp 3′-UTR, and a 1485 bp ORF
Summary
Environmental factors, especially salinity, in intertidal zones fluctuated acutely owing to tides, rainfall, surface runoff and so on. Osmoconforming marine animals can result in large changes in the osmotic concentration of hemolymph in order to adapt to fluctuations in salinity of ambient seawater[1, 2]. One of the primary strategies of osmoconforming animals to keep the osmotic balance is the manipulation of intracellular levels of organic osmolytes, especially free amino acids[3]. As organic osmolytes, maintain osmotic balance between extracellular and intracellular fluids in marine species[5]. One way includes the oxidation of cysteine to cysteine sulfinic acid (CSA) by cysteine dioxygenase (CDO), and decarboxylation to hypotaurine by cysteine sulfinate decarboxylase (CSAD) In this pathway, CSAD has been characterized as the key enzyme that determines taurine biosynthesis capability[15, 16]. Hypotaurine and taurine are abundant in mollusc, the biosynthesis pathway remains unclear
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