Molecular cloning and characterization of Pif gene from pearl mussel, Hyriopsis cumingii, and the gene expression analysis during pearl formation
In the present study, the Pif gene of the freshwater pearl aquaculture mussel, Hyriopsis cumingii (HcPif) was successfully cloned and functionally characterized. The full sequence of HcPif gene consists of 3415 base pairs, which putatively encode two proteins, HcPif90 and HcPif80. A sequence analysis revealed that HcPif contained a von Willebrand factor type A domain and a chitin-binding domain, and shared many functional residues with other Pif homologues. A highly conserved sequence, FKGLDEIELML, at the C-terminus of Pif80s was identified as the key functional site. The corresponding peptide fragment markedly modified the morphology of calcite crystallites in CaCO3 crystallization assay and might play an essential role in the interactive binding between HcPif80 and CaCO3. Moreover, real-time PCR results showed that HcPif gene was dominantly expressed in the pearl secreting tissues and its expression changed in response to the different development status of the pearl sac during pearl aquaculture. The gene expression of HcPif was maximum 7 days after mantle grafting and declined to about the control level on day 30. Our in vitro and in vivo experimental data indicated that HcPif gene possessed the inherent characteristics of a nacre formation gene and its expression might faithfully reflect the pearl secretion status of the pearl mussels examined. Our findings may extend the understanding of the biomineralization mechanism of nacre formation and provide a potential biomarker for pearl farming.
KeywordsPif Hyriopsis cumingii Biomineralization Pearl aquaculture
This study was supported by the Natural Science Foundation of Jiangsu province (Grant no BK20130496), Natural Science Foundation of the Jiangsu Higher Education Institutions of China (Grant no 13KJB240001), Scientific Research Foundation for Returned Scholars, Ministry of Education of China and Startup Foundation for Advanced Talents of Jiangsu University (Grant no 13JDG006). Dr. Rui Zhang was supported by the National Natural Science Foundation of China (Grant no 81300673), Startup Foundation for Advanced Talents of Jiangsu University (Grant no 13JDG004), and Cultivation Project for Young Core Teacher of Jiangsu University.
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Conflict of interest
The authors declare that there is no conflict of interest regarding the publication of this article.
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