Zhang Yukun, Liu Zhaoqun, Song Xiaorui, Huang Shu, Wang Lingling, Song Linsheng
Liaoning Key Laboratory of Marine Animal Immunology, Dalian Ocean University, Dalian, China.
Liaoning Key Laboratory of Marine Animal Immunology and Disease Control, Dalian Ocean University, Dalian, China.
Front Physiol. 2019 Aug 13;10:1034. doi: 10.3389/fphys.2019.01034. eCollection 2019.
The biosynthesis of a calcified shell is critical for the development of oyster larvae. This process can be severely inhibited by CO-induced ocean acidification, causing mass mortality of oyster larvae. However, the underlying molecular mechanism of such process has not been well explored until now. In the present study, a homolog of chitin synthase (named as chs1) and a homolog of chitinase (named as chit4) were identified from the Pacific oyster . The cDNA sequences of chs1 and chit4 were of 813 bp and 2118 bp, encoding a putative polypeptide of 271 amino acids and 706 amino acids, respectively. There were a Chitin_synth_2 domain and a Glyco_18 domain in the inferred amino acid sequences of chs1 and chit4, respectively. Both chs1 and chit4 shared high sequence identity with their homologs in vertebrates. In addition, when oyster larvae were exposed to acidification treatment (pH 7.4), their shell biosynthesis process was seriously restrained. The expression level of chs1 mRNA was significantly suppressed while that of chit4 was dramatically activated upon acidification treatment. chs1 and chit4 are critical enzymes for chitin metabolism, and such changes in their mRNA expression could result in the decrease of chitin content in oyster larvae's shells, which might lead to the failure of shell formation. Therefore, results in the present study suggested that acidified seawater might inhibit the formation of oyster calcified shell by suppressing the biosynthesis of chitin.
钙化壳的生物合成对于牡蛎幼虫的发育至关重要。这一过程会受到CO诱导的海洋酸化的严重抑制，导致牡蛎幼虫大量死亡。然而，迄今为止，这一过程的潜在分子机制尚未得到充分探索。在本研究中，从太平洋牡蛎中鉴定出一种几丁质合酶的同源物（命名为chs1）和一种几丁质酶的同源物（命名为chit4）。chs1和chit4的cDNA序列分别为813 bp和2118 bp，分别编码一个推定的271个氨基酸和706个氨基酸的多肽。chs1和chit4的推断氨基酸序列中分别有一个Chitin_synth_2结构域和一个Glyco_18结构域。chs1和chit4与它们在脊椎动物中的同源物都具有高度的序列同一性。此外，当牡蛎幼虫暴露于酸化处理（pH 7.4）时，它们的壳生物合成过程受到严重抑制。酸化处理后，chs1 mRNA的表达水平显著受到抑制，而chit4的表达水平则被显著激活。chs1和chit4是几丁质代谢的关键酶，它们mRNA表达的这种变化可能导致牡蛎幼虫壳中几丁质含量的降低，这可能导致壳形成失败。因此，本研究结果表明，酸化海水可能通过抑制几丁质的生物合成来抑制牡蛎钙化壳的形成。
