Novel globular C1q domain-containing protein (PmC1qDC-1) participates in shell formation and responses to pathogen-associated molecular patterns stimulation in Pinctada fucata martensii

Xinwei Xiong,Xiaodong Du,Xiaodong Du,Xiaodong Du,Xiaodong Du,Zhe Zheng,Zhe Zheng,Chuyi Li

doi:10.1038/s41598-020-80295-0

Xinwei Xiong, Xiaodong Du + Show 6 more

Open Access

https://doi.org/10.1038/s41598-020-80295-0

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Abstract

The C1q protein, which contains the globular C1q (gC1q) domain, is involved in the innate immune response, and is found abundantly in the shell, and it participates in the shell formation. In this study, a novel gC1q domain-containing gene was identified from Pinctada fucata martensii (P. f. martensii) and designated as PmC1qDC-1. The full-length sequence of PmC1qDC-1 was 902 bp with a 534 bp open reading frame (ORF), encoding a polypeptide of 177 amino acids. Quantitative real-time PCR (qRT-PCR) result showed that PmC1qDC-1 was widely expressed in all tested tissues, including shell formation-associated tissue and immune-related tissue. PmC1qDC-1 expression was significantly high in the blastula and gastrula and especially among the juvenile stage, which is the most important stage of dissoconch shell formation. PmC1qDC-1 expression was located in the outer epithelial cells of mantle pallial and mantle edge and irregular crystal tablets were observed in the nacre upon knockdown of PmC1qDC-1 expression at mantle pallial. Moreover, the recombined protein PmC1qDC-1 increased the rate of calcium carbonate precipitation. Besides, PmC1qDC-1 expression was significantly up-regulated in the mantle pallial at 6 h and was significantly up-regulated in the mantle edge at 12 h and 24 h after shell notching. The expression level of PmC1qDC-1 in mantle edge was significantly up-regulated at 48 h after LPS stimulation and was significantly up-regulated at 12 h, 24 h and 48 h after poly I:C stimulation. Moreover, PmC1qDC-1 expression was significantly up-regulated in hemocytes at 6 h after lipopolysaccharide (LPS) and poly I:C challenge. These findings suggest that PmC1qDC-1 plays a crucial role both in the shell formation and the innate immune response in pearl oysters, providing new clues for understanding the shell formation and defense mechanism in mollusk.

Highlights

C1q protein, a versatile recognition protein, binds to a wide variety of immune and non-immune ligands[1,2] via the C-terminal globular C1q (gC1q) domain
C1q is the key component of complement system containing the typical C-terminal globular C1q domain
We identified a novel gC1q gene from P. f. martensii and designated it as PmC1qDC-1

Summary

Introduction

C1q protein, a versatile recognition protein, binds to a wide variety of immune and non-immune ligands[1,2] via the C-terminal gC1q domain. C1q domain-containing (C1qDC) proteins can be synthesized and secreted locally by various cell types, including macrophages, dendritic cells, fibroblasts, and mast cells that are ubiquitously distributed throughout the body[12], to participate in the immune process They can be synthesized from specific tissues and organs such as microglial cells, glomerular and tubular cells, osteoclasts, and trophoblasts[13] and are involved in the regulation of multiple cellular functions such as cell growth, clearance of the apoptotic cells, and promotion of cell adhesion[14]. In Hyriopsis cumingii, a kunitz proteinase inhibitor participated in antimicrobial process duiring pearl sac formation and induced the overgrowth of calcium carbonate[36] This show that there is no adversative relation in the roles between immune and biomineralization.Views on biochemical d efense[34], gastropod shell has been co-opted as a defense system against parasitic n ematodes[37]. Investigating the biomineralized and immunological function of PmC1qDC-1 in P. f. martensii may provide new insights into the roles of C1qDC proteins in shell formation and defense mechanism of mollusks

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