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Date:2021-02-08Read:10

Giant Breakthrough Accomplished in the Study of Molluscan Red-bloodedness in the Blood Clam Tegillarca Granosa

A recent news reports a giant breakthrough in the study of the blood clam Tegillarca granosa made by the team of professor Lin Zhihua and Bao Yongbo of Zhejiang Wanli University and Academician Bao Zhenmin’s team of Chinese Ocean University. The result of their scientific study, a paper named “Genomic insights into the origin and evolution of molluscan red-bloodedness in the blood clam Tegillarca granosa”, was published in the top magazine of the field—Molecular Biology and Evolution on February 2nd.

The study first presents the first chromosome-level genome and comprehensive transcriptomes of the blood clam Tegillarca granosa for an integrated genomic, evolutionary and functional analyses of clam RB phenotype. Then it identifies blood clam-specific and expanded gene families, as well as gene pathways that are of RB relevant. According to the study, Clam-specific RB-related hemoglobins (Hbs) show close phylogenetic relationships with myoglobins (Mbs) of blood clam and other molluscs without the RB phenotype, indicating that clam-specific Hbs are likely evolutionarily derived from the Mb lineage. An important finding of the study is that similar to vertebrate Hbs, blood clam Hbs are present in a form of gene cluster. It shows the fact that despite the convergent evolution of Hb clusters in blood clam and vertebrates, their Hb clusters may have originated from a single ancestral Mb-like gene as evidenced by gene phylogeny and synteny analysis. Therefore, a full suite of enzyme-encoding genes for heme synthesis can be identified in blood clam, with prominent expression in hemolymph and resembling those in vertebrates, suggesting a convergence of both RB-related Hb and heme functions in vertebrates and blood clam. RNAi experiments confirm the functional roles of Hbs and key enzyme of heme synthesis in the maintenance of clam RB phenotype. The high-quality genome assembly and comprehensive transcriptomes presented herein serve new genomic resources for the super-diverse phylum Mollusca, and provide deep insights into the origin and evolution of invertebrate RB.

With Professor Bao Yongbo and Associate Professor Zeng Qifan as the first authors of the paper and Professor Lin Zhihua and Professor Wang Shi as corresponding authors, this scientific research is a significant fruit of strategic collaboration between Zhejiang Wanli University and Ocean University of China. Funded by the National Shellfish Technology System, this project has also been confirmed as program of National Natural Science Foundation, key program of Provincial Natural Science Foundation, and China’s key program of research and development.