The shell formation mechanism of Turbo argyrostomus based on ultrastructure and transcriptome analysis.

The gold inner shell of Turbo argyrostomus is an important morphological classification characteristic in Gastropoda. However, the gene sets responsible for shell formation in gastropods remain poorly explored. In this study, we investigated the microstructure using scanning electron microscopy (SEM), hematoxylin-eosin (HE) and Alcian blue staining-periodic acid-Schiff (AB-PAS) staining. The SEM results illustrated that the T. argyrostomus shell exhibited a special "sandwich" microstructure. The results of histological observation demonstrated two major cell types: adipocytes and mucin cells. A total of 318 differentially expressed genes were identified between edge mantle and central mantle, among which whey acidic protein, N66, and nacre-like proteins, and Lam G and EGF domains may be related to shell microstructure. 22.39% - 25.20% of the mucin genes had biomineralization related domains, which supported for the relationship between mucins and shell formation. Moreover, this study revealed energy distribution differences between the edge mantle and central mantle. These results provide insights for further understanding of the biomineralization mechanism in Gastropoda.

The mechanisms involved in byssogenesis in Pteria penguin under different temperatures.

Byssus is important for marine bivalves to adhere robustly to diverse substrates and resist environmental impacts. The winged pearl oyster, Pteria penguin, can reattach or not reattach to the same environment, which leaves the development and survival of the oyster population at risk. In this study, diverse methods were employed to evaluate the byssus quality and explore the mechanism of byssus secretion at different temperatures. The results demonstrated that oysters maintained their byssus properties at different temperatures through polyphenol oxidase (PPO) and reactive oxygen species (ROS) variation. They were both higher at 27 °C than at 21 °C. Furthermore, PPO activities of WB27 (31.78 U/g ± 1.50 U/g) were significantly higher than NB27, WB21, and NB21. Sectional observation revealed three types of vesicles, from which a novel vesicle might participate in byssogenesis as a putative metal storage particle. Moreover, cytoskeletal proteins may cooperate with cilia to transport byssal proteins, which then facilitate byssus formation under the regulation of upstream signals. Transcriptome analysis demonstrated that protein quality control, ubiquitin-mediated proteolysis, and cytoskeletal reorganization-related genes contributed to adaptation to temperature changes and byssus fabrication, and protection-related genes play a critical role in byssogenesis, byssus toughness, and durability. These results were utilized to create a byssogenesis mechanism model, to reveal the foot gland and vesicle types of P. penguin and provide new insights into adaptation to temperature changes and byssus fabrication in sessile bivalves.