Our study on the origin and evolution of molluscan red-bloodedness was published in MBE

On February 2, 2021, we published the latest research "Genomic insights into the origin and evolution of molluscan red-bloodedness in the blood clam Tegillarca granosa" in Molecular Biology and Evolution. Many thanks to our collaborators of Lin's team from Zhejiang Wanli University. This study is an important achievement supported by the strategic cooperation between Ocean University of China and Zhejiang Wanli University.

Blood clams differ from their molluscan kins by exhibiting a unique red-blood (RB) phenotype; however, the genetic basis and biochemical machinery subserving this evolutionary innovation remain unclear. As a fundamental step toward resolving this mystery, we presented 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. We identified blood clam-specific and expanded gene families, as well as gene pathways that are of RB relevant. Clam-specific RB-related hemoglobins (Hbs) showed close phylogenetic relationships with myoglobins (Mbs) of blood clam and other molluscs without the RB phenotype, indicating that clam-specific Hbs were likely evolutionarily derived from the Mb lineage. Strikingly, similar to vertebrate Hbs, blood clam Hbs were present in a form of gene cluster. 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. A full suite of enzyme-encoding genes for heme synthesis was 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. RNA interference experiments confirmed 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.

Prof. Shi Wang of Ocean University of China and Researcher Zhihua Lin of Zhejiang Wanli University are the co-corresponding authors of this paper. The research is supported by the National Science Foundation of China and the National Key Research and Development Program of China.

(A) Global genome landscape of T. granosa; (B) Classification and distribution of globin family in molluscs; (C) Micro-synteny of conserved Hb cluster flanking genes among blood clam, chicken, and human

Link to the paper:

https://academic.oup.com/mbe/advance-article-abstract/doi/10.1093/molbev/msab030/6126415