Cloning of a HcCreb gene and analysis of its effects on nacre color and melanin synthesis in Hyriopsis cumingii.

Mengying Zhang,Jinpan Zhang,Jiale Li,Xiajun Chen,Zhiyi Bai,Alexander Chong Shu-Chien

doi:10.1371/journal.pone.0251452

Abstract

Creb (Cyclic AMP response element binding protein) is a nuclear regulatory factor that regulates transcription through autophosphorylation. In melanocytes, cAMP’s corresponding elements bind to the Creb protein to autophosphorylation and activate MITF (Microphthalmia-associated transcription factor). MITF stimulates Tyrosine(tyr) to induce melanocytes to differentiate into eumelanin and pheomelanin. In this study, a HcCreb gene in Hyriopsis cumingii was cloned and its effects on melanin synthesis and nacre color were studied. HcCreb was expressed in both purple and white mussels, and there was a significant difference in expression between adductor muscle (p<0.01) and mantle tissue (p<0.05). Other tissues did not show significant differences (except for gill tissue), and in general, the level of mRNA expression was higher in purple mussels than in white mussels. In both white and purple mussels expression levels in gill tissue was the highest, followed by the mantle. Strong and specific mRNA signals were detected in the dorsal epithelial cells of the mantle pallial layer, indicating that HcCreb may be involved in nacre formation. After arbutin treatment, the expression of HcCreb decreased significantly. By further testing the changes in mantle melanin content it was found that the melanin content after arbutin treatment decreased significantly compared to the control group (p<0.05). It is speculated that the HcCreb gene plays a role in the process of melanin synthesis and nacre color formation in H. cumingii.

Highlights

Hyriopsis cumingii is a freshwater mussel that can produce high-quality freshwater pearls and is currently accounting for 95% of China’s pearl production [1]
Through the analysis of Except for gill tissue, the level of mRNA expression of the other tissues in purple mussels was higher than that in white mussels it was found that HcCreb is expressed in the mantle, adductor muscle, gills, foot, and hepatopancreas of H.cumingii, and that the expression level is higher in the gill and mantle
Strong and specific positive hybridization signals were detected in the dorsal epithelial cells of the mantle pallial layer, indicating that HcCreb may be involved in nacre formation

Summary

Introduction

Hyriopsis cumingii is a freshwater mussel that can produce high-quality freshwater pearls and is currently accounting for 95% of China’s pearl production [1]. Existing research data do not provide a systematic and clear description of the process regulating nacre color formation, factors such as metal elements, porphyrins, carotenoids, melanin and physical structure may play an important role [5]. Jiang et al [6] compared and analyzed the metal elements present in the mantle and interstitial fluid of H. cumingii of different colors and found that nacre color is correlated with the content of Fe, Mg, Co, and Mn. Zhang et al [7] found that pearl color is mainly determined by porphyrin and metalloporphyrin, while Li et al [8] found that by adding carotenoids, the ability to accumulate carotenoids was higher in purple line mussels than in white line mussels. Shen [9] cloned a Mitf gene in H. cumingii, and found that the cloned gene, HcMitf, plays an important role in melanin synthesis, nacre formation and shell pigmentation

Methods

Results

Conclusion