Proteomic characterisation of byssus components in the pearl oyster, Pinctada maxima

Many bivalve species produce groups of strong proteinaceous byssal threads to rigidly attach to underwater substrates. Fibres like these have potential applications as biomedical materials due to their unique mechanical characteristics. The byssus and byssal thread producing glands of Pinctada maxima have not yet been characterised. RNA was isolated from P. maxima foot and byssal stem region tissues and sequenced using the Illumina platform. A de novo reference transcriptome comprising 34,281 contiguous sequences was assembled, and tissue replicates were mapped against the reference for quantitative analysis. Tryptic digests of byssal threads were analysed by LC-MS/MS. The resultant peptides were matched to 62 protein sequences derived from our reference transcriptome. Components of the byssus were identified for further characterisation, including a highly expressed perlucin-like foot protein (Pmfp1) and a recently identified protein that we refer to herein as glycine-rich thread (GRT) protein. This work provides principal knowledge on the molecular components of the byssus for P. maxima and the foot ultrastructure involved in the creation of byssal threads. This study advances our knowledge of byssus biosynthesis in non-mytilids, providing a platform for the design of new marine biopolymers.

诸多双壳类动物可分泌多组坚固的蛋白质足丝（proteinaceous byssal threads），以此将自身牢固附着于水下基底之上。这类纤维凭借其独特的力学特性，具备用作生物医用材料的应用潜力。目前针对大珠母贝（Pinctada maxima）的足丝及其分泌足丝的腺体，尚未开展系统的表征研究。研究人员从大珠母贝的足及足丝茎部组织中提取RNA，并通过Illumina测序平台（Illumina platform）完成测序。本研究组装得到包含34281条连续序列的从头组装参考转录组（de novo reference transcriptome），并将组织重复样本比对至该参考转录组以开展定量分析。采用液相色谱-串联质谱（LC-MS/MS）对足丝的胰蛋白酶酶解产物进行分析后，最终得到的肽段可匹配到源自本研究参考转录组的62条蛋白质序列。研究鉴定出足丝的多种组分以待进一步表征，其中包括高表达的类珠母素足蛋白（perlucin-like foot protein, Pmfp1）以及本研究中新命名的富甘氨酸丝蛋白（glycine-rich thread protein, GRT）。本研究为阐明大珠母贝足丝的分子组分以及参与足丝形成的足部超微结构提供了核心理论依据，同时深化了我们对非贻贝类生物足丝生物合成机制的认知，为新型海洋生物聚合物的设计研发提供了研究基础。