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The Betta fish displays a remarkable variety of phenotypes selected during domestication. However, the genetic basis underlying these traits remains largely unexplored. Here, we report a high-quality genome assembly and resequencing of 727 individuals representing diverse morphotypes of the Betta fish. We show that current breeds have a complex domestication history with extensive introgression with wild species. Using a genome-wide association study, we identify the genetic basis of multiple traits, including coloration patterns, the "Dumbo" phenotype with pectoral fin outgrowth, extraordinary enlargement of body size that we map to a major locus on chromosome 8, the sex determination locus that we map to

The Betta fish displays a remarkable variety of phenotypes selected during domestication. However, the genetic basis underlying these traits remains largely unexplored. Here, we report a high-quality genome assembly and resequencing of 727 individuals representing diverse morphotypes of the Betta fish. We show that current breeds have a complex domestication history with extensive introgression with wild species. Using a genome-wide association study, we identify the genetic basis of multiple traits, including coloration patterns, the “Dumbo” phenotype with pectoral fin outgrowth, extraordinary enlargement of body size that we map to a major locus on chromosome 8, the sex determination locus that we map to dmrt1 , and the long-fin phenotype that maps to the locus containing kcnj15 . We also identify a polygenic signal related to aggression, involving multiple neural system-related genes such as esyt2 , apbb2 , and pank2 . Our study provides a resource for developing the Betta fish as a genetic model for morphological and behavioral research in vertebrates.

To investigate the regulation of metallothionein genes (HsMTs) of Hyriopsis schlegelii, 1,121-bp and 1,270-bp regions of the HsMT1 and HsMT2 promoters were cloned and analyzed, respectively. The two promoters shared partially conserved features and possessed distinct characteristics such as the number or position of metal response elements (MREs). Further analysis of the HsMT1 and HsMT2 promoters was performed by the reporter assay using the luciferase gene. Both promoters were activated by various metals, and presented different levels of metal ions inducibility in human hepatoblastoma cells. Deletion mutant assays demonstrated that both the longest promoter regions achieved the maximum inducibility, and the metal inducibility was dependent on the presence of the MRE in HsMT1 and the distal MRE in HsMT2. In addition, we cloned a putative metal responsive transcription factor (hereby designated as HsMTF-like) and studied its effect on HsMTs expression in human hepatoblastoma cells. An in vivo assay demonstrated that HsMTF-like activates basal HsMTs transcription level, and the MRE in the HsMTs promoter mediates this activation process. Moreover, this basal transcription level can be further boosted by zinc treatment. In conclusion, the regulation mechanism for MT activation in H. schlegelii should be evolutionarily conserved.

Calmodulin (CaM) is a pivotal multifunction regulator of calcium metabolism in nearly all organisms, and earlier studies revealed its underlying involvement of shell or pearl formation in oysters. Culture pearls are formed within complete pearl sacs. However, whether CaM functions in pearl sac formation or not is not reported. In this study, we prepared a polyclonal antibody against the CaM from the freshwater pearl mussel Hyriopsis schlegelii (HsCaM) and then detected the expression and distribution of HsCaM in pearl sac using the method of immunofluorescence in situ hybridization (IISH). Results revealed that strong fluorescent signals were observed in pearl sac as well as epithelial border of mantle. In addition, quantitative analysis results indicated that the mRNA expression level of HsCaM in pearl sac of H. schlegelii was significantly up-regulated during pearl sac formation. The fact that HsCaM highly expressed is present in pearl sac suggested that it might facilitate pearl sac formation in H. schlegelii.