Molecular cloning and characterization of Pif gene from pearl mussel, Hyriopsis cumingii, and the gene expression analysis during pearl formation

Abstract

In the present study, the Pif gene of the freshwater pearl aquaculture mussel, (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 CaCO crystallization assay and might play an essential role in the interactive binding between HcPif80 and CaCO. 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.

More than 90% of nacre matrix proteins are composed of silk-like proteins

“…Chitin-binding domains were found in six proteins in the nacre proteome, hichin, hc-pif2, hic124, hic92, hic54, and chitinase-4 (table 2). hc-pif2 had eight amino acids mutation with pif previously reported in H. cumingii 39 , and a "DIYKRKDRDYQS" amino acids sequence was missing in hc-pif2 (Figure S12).…”

The Application of Pearls in Traditional Medicine of China and Their Chemical Constituents, Pharmacology, Toxicology, and Clinical Research

“…One is the irregular CaCO 3 deposition on the bare nucleus; the second is that the deposition of CaCO 3 becomes more and more regular until a mature nacre is formed on the nucleus, similar to the regeneration of shells ( Sato and Komaru, 2019 ). Pearl formation takes about 2–3 years and is related to the expression and release of a variety of genes and proteins, such as the Hic14 gene ( Jin et al, 2019 ), Hic19 gene ( Jin et al, 2019 ), Pif80 gene ( Zhang et al, 2018 ), Pmarg-Pearlin matrix protein ( Bourrat et al, 2012 ), and pearl shell matrix protein gene ( Cartwright et al, 2013 ). These genes and proteins jointly regulate the formation of pearls, such as their growth, shape, and size.…”