柯才煥教授課題組近日在Scientific Reports期刊發表題為“Transcriptome analysis of the key role of GAT2 gene in the hyper-accumulation of copper in the oyster Crassostreaangulata”研究論文，研究了影響牡蠣銅累積的關鍵基因并闡述了牡蠣銅富集個體差異的形成機制。
牡蠣對銅、鋅等金屬具有非常強的富集能力，經常被用于指示河口污染情況。隨著工業發展，近岸河口區遭受越來越嚴重的銅污染。因此牡蠣對銅的超富集現象越來越被人們所關注。牡蠣對銅富集存在非常大的個體差異，然而相關的研究卻非常有限，特別是缺少分子機制的解析。
本研究以福建牡蠣(Crassostrea angulata)作為研究對象，選取了兩組存在銅富集差異（3-4倍）福建牡蠣的組織進行基因轉錄水平分析。通過對差異基因的分析，建立了如下科學假設：牡蠣神經遞質轉運體基因的差異表達(GAT2基因)，可以影響牡蠣神經系統調控的生理行為，從而改變銅的富集動力學過程，產生銅富集個體差異現象；銅離子結合、轉運相關的基因(ABCB家族、Laccase家族、載脂蛋白基因)表達量顯著上調，則使銅富集量高的牡蠣個體能夠保證細胞內銅穩態，免受銅的毒害（圖1所示）。
為了驗證這個設想，選取神經遞質轉運體GAT2基因進一步研究。發現在該基因沉默后，牡蠣鰓和外套膜中銅富集量顯著降低，而在GABA受體拮抗劑注射后牡蠣銅富集量顯著升高。GAT2基因的表達差異可能是引起牡蠣銅富集個體差異的關鍵因素，GAT2轉運體可以通過調節牡蠣體內GABA對神經系統的刺激來控制牡蠣的行為，像濾水、排泄等活動，而這些行為都會影響銅吸收或者外排的動力學過程。
本研究首次發現神經遞質轉運體在貝類金屬累積中起到重要作用，豐富了海洋雙殼類金屬富集的分子機制。對牡蠣銅富集個體差異的解析，也為進一步培育銅富集量低的牡蠣品系提供理論基礎。
Citation:Bo Shi, Zekun Huang, Xu Xiang, Miaoqin Huang, Wen-Xiong Wang, and Caihuan Ke*. Transcriptome analysis of the key role of GAT2 gene in the hyper-accumulation of copper in the oyster Crassostrea angulata. Scientific Reports. Doi: 10.1038/srep17751
Abstract：
One paradigm of oysters as the hyper-accumulators of many toxic metals is the inter-individual variation of metals, but the molecular mechanisms remain very elusive. A comprehensive analysis of the transcriptome of Crassostreaangulata was conducted to reveal the relationship between gene expression and differential Cu body burden in oysters. Gene ontology analysis for the differentially expressed genes showed that the neurotransmitter transporter might affect the oyster behavior, which in turn led to difference in Cu accumulation. The ATP-binding cassette transporters superfamily played an important role in the maintenance of cell Cu homeostasis, vitellogenin and apolipophorin transport, and elimination of excess Cu. Gill and mantle Cu concentrations were significantly reduced after silencing the GABA transporter 2 (GAT2) gene, but increased after the injection of GABA receptor antagonists, suggesting that the function of GABA transporter 2 gene was strongly related to Cu accumulation. These findings demonstrated that GABA transporter can control the action of transmitter GABA in the nervous system, thereby affecting the Cu accumulation in the gills and mantles.
Link to full text: http://www.nature.com/articles/srep17751
