海洋酸化会导致贝壳严重溶解,威胁海洋软体动物的生存。软体动物的骨膜由蛋白质和多糖等大分子组成,并保护内壳层免受溶解和微生物侵蚀。此外,它作为壳沉积的主要模板。然而,骨膜的化学成分和形成机制尚不清楚。在这项研究中,我们应用了转录组学,蛋白质组学,物理,和化学分析来解开绿色贻贝PernaviridisLinnaeus中骨膜形成的奥秘。FTIR分析表明,骨膜层为以多糖为主的有机膜,脂质,和蛋白质,类似于外壳矩阵。有趣的是,蛋白质组学研究确定了富含酪氨酸和一些在酪氨酸氧化中进化的酶的成分,表明酪氨酸氧化可能在骨膜形成中起重要作用。此外,比较转录组学表明,富含酪氨酸的蛋白质在骨膜沟中大量合成。分泌后,骨膜蛋白在海水中被氧化逐渐晒黑,ATR-FTIR显示交联水平显著增加。我们的研究揭示了双壳软体动物骨膜层的化学成分和推定的鞣制机理。意义:骨膜层,在壳生物矿化的启动中起着至关重要的作用,在不断变化的全球气候中,保护矿物免受软体动物的溶解,尤其是海洋酸化条件。然而,骨膜形成的分子机制尚不完全清楚。在这项研究中,我们发现,酪氨酸酶对富含酪氨酸的蛋白质的氧化和交联参与了绿色贻贝Pernaviridis中骨膜的形成。这项研究为贻贝壳形成的第一步以及绿藻对不同栖息地的强大适应提供了一些见解。这些发现还有助于揭示双壳类动物对预计酸化海水的潜在适应。
Ocean acidification causes severe shell dissolution and threats the survival of marine molluscs. The periostracum in molluscs consists of macromolecules such as proteins and polysaccharides, and protects the inner shell layers from dissolution and microbial erosion. Moreover, it serves as the primary template for shell deposition. However, the chemical composition and formation mechanism of the periostracum is largely unknown. In this study, we applied transcriptomic, proteomics, physical, and chemical analysis to unravel the mysteries of the periostracum formation in the green mussel
Perna viridis Linnaeus. FTIR analysis showed that the periostracum layer was an organic membrane mainly composed of polysaccharides, lipids, and proteins, similar to that of the shell matrix. Interestingly, the proteomic study identified components enriched in tyrosine and some enzymes that evolved in tyrosine oxidation, indicating that tyrosine oxidation might play an essential role in the periostracum formation. Moreover, comparative transcriptomics suggested that tyrosine-rich proteins were intensively synthesized in the periostracum groove. After being secreted, the periostracum proteins were gradually tanned by oxidation in the seawater, and the level of crosslink increased significantly as revealed by the ATR-FTIR. Our present study sheds light on the chemical composition and putative tanning mechanism of the periostracum layer in bivalve molluscs. SIGNIFICANCE: The periostracum layer, plays an essential role in the initiation of shell biomineralization, the protection of minerals from dissolution for molluscs and especially ocean acidification conditions in the changing global climate. However, the molecular mechanism underlying the periostracum formation is not fully understood. In this study, we revealed that the oxidation and cross-link of tyrosine-rich proteins by tyrosinase are involved in periostracum formation in the green mussel
Perna viridis. This study provides some insights into the first step of mussel shell formation and the robust adaptation of P. viridis to diverse habitats. These findings also help to reveal the potential acclimation of bivalves to the projected acidifying seawater.