Identification and expression analysis of the MSP130-related-2 gene from Hyriopsis cumingii.

MSP130-related-2 is thought to play a role in bio-mineralization as revealed in Crassostrea gigas and sea urchins. In this study, an MSP130-related-2 gene was isolated from Hyriopsis cumingii (HcMSP130-related-2) and characterized for the first time. The HcMSP130-related-2 cDNA was 2307 bp in length and consisted of a 572-bp 5'-untranslated region (5'-UTR), a 1239-bp open reading frame encoding 430-amino acid residues, and a 439-bp 3'-UTR. The molecular weight of the peptide was predicted to be 48551.3 Da, with a theoretical isoelectric point of 4.78 and instability index of 32.74, indicating that the protein is stable. The HcMSP130-related-2 amino acid residues included a signal peptide and several potential N-glycosylation sites. NCBI BLAST analysis indicated that this full-length amino acid sequence showed the highest similarity with HcMSP130-related-2 from C. gigas (45%) and about 38% identity with that from SpMSP130-rel-2 and Strongylocentrotus purpuratus. A phylogenetic tree showed that HcMSP130-rel-2 clustered with MSP130 from C. gigas. HcMSP130-related-2 was expressed in various tissues, including the mantle, blood, gill, foot, liver, kidney, intestine, and muscle, with the highest transcripts found in the mantle. Quantitative real-time polymerase chain reaction was used to analyze the expression of the HcMSP130- related-2 gene in grass carp after inducing shell damage. HcMSP130- related-2 expression was upregulated significantly in the mantle within 7 days (P < 0.05) after damage; however, the expression remained unchanged in the adductor muscle tissues (P > 0.05). These data suggest that HcMSP130-related-2 might be involved in shell formation in H. cumingii.

Molecular characterization and expression pattern of an α-amylase gene (HcAmy) from the freshwater pearl mussel, Hyriopsis cumingii.

The freshwater pearl mussel Hyriopsis cumingii is of commercial importance because it produces the freshwater pearl; however, knowledge about the molecular characterization and regulation mechanisms of α-amylase remains unknown for this species. In this study, the full-length cDNA of the α-amylase gene (HcAmy) was isolated from H. cumingii by the rapid amplification of cDNA ends. Tissue-specific expression analysis showed that HcAmy mRNA was mainly expressed in the hepatopancreas; although, the gene was also expressed in the adductor muscle, intestine, gill, and crystalline style. After 2 weeks starvation, the expression of HcAmy mRNA in the hepatopancreas was upregulated at 24 h after re-feeding or when exposed to algal concentration of 32 µg/L chlorophyll-a, indicating that the HcAmy mRNA expression in H. cumingii is regulated by algal availability. The results of this study confirm that the HcAmy gene is an important component of the carbohydrate metabolism of H. cumingii fed phytoplankton. In addition, this study demonstrates that the modulation of this gene is dependent on environmental food availability, including starvation, re-feeding time following a period of starvation, and algal concentrations during re-feeding.

Two chitin metabolic enzyme genes from Hyriopsis cumingii: cloning, characterization, and potential functions.

Chitin, the second most important natural polymer in the world, and its N-deacetylated derivative chitosan are found in a wide variety of organisms. These versatile biopolymers are associated with a broad range of biological functions. This article is the first to report the potential functions of 2 chitin metabolic enzyme genes from Hyriopsis cumingii. A chitinase-3 gene (Chi-3) and a chitin deacetylase gene (Cda) were cloned from H. cumingii and characterized. Semi-quantitative reverse transcription polymerase chain reaction analysis revealed that the Cda gene was expressed in blood, mantle, liver, stomach, kidney, intestine, gill, and foot, whereas Chi-3 was also expressed in those tissues but not in blood. The tissue-specific expression of H. cumingii Chi-3 indicated that other Chi genes may be involved in the H. cumingii immune system. Real-time quantitative polymerase chain reaction analysis showed that the expression of Chi-3 was significantly (P < 0.05) upregulated 12 h after shell damage, suggesting that Chi-3 might hydrolyze superfluous chitin after shell recovery and play a role in shell formation. Conversely, Cda expression did not change significantly (P > 0.05) to maintain a certain degree of acetylation in chitin/chitosan. This study enriches the basic research on chitin metabolic genes and lays foundations for further research of shell regeneration in mussels.