The Symbiodinium kawagutii genome illuminates dinoflagellate gene expression and coral symbiosis

Publish Date:2016-08-30Scan Num:58

Prof. Senjie Lin from college of Ocean and Earth Sciences,Xiamen Univeristy has published the paper “The Symbiodinium kawagutii genome illuminates dinoflagellate gene expression and coral symbiosis” in Science June,2015 as corresponding author.The main content of the article are as follows:

Many corals have formed mutualistic associations with dinoflagellate symbionts, which are thought to provide nutrients and other benefits. To examine the underlying genetics of this association, S. Lin et al. sequenced the genome of the endosymbiont dinoflagellate Symbiodinium kawagutii. The genome includes gene number expansions and encodes microRNAs that show complementarity to genes within the coral genome. Such microRNAs may be involved in regulating coral genes. Furthermore, coral and S. kawagutii appear to share homologs of genes encoding specific nutrient transporters. The findings shed light on how symbiosis is established and maintained between dinoflagellates and corals.

Dinoflagellates are important components of marine ecosystems and essential coral symbionts, yet little is known about their genomes. They report here on the analysis of a high-quality assembly from the 1180-megabase genome of Symbiodinium kawagutii. They annotated protein-coding genes and identified Symbiodinium-specific gene families. No whole-genome duplication was observed, but instead we found active (retro)transposition and gene family expansion, especially in processes important for successful symbiosis with corals. They also documented genes potentially governing sexual reproduction and cyst formation, novel promoter elements, and a microRNA system potentially regulating gene expression in both symbiont and coral. We found biochemical complementarity between genomes of S. kawagutii and the anthozoan Acropora, indicative of host-symbiont coevolution, providing a resource for studying the molecular basis and evolution of coral symbiosis.

Globally, analysis revealed extensive genomic innovation in dinoflagellates. A total of 25,112 gene families were clustered from the genomes ofS. kawagutiiand eight other species representing higher plants, chlorophytes, rhodophytes, diatoms, phaeophytes, alveolates, and cnidarians.S. kawagutiihas 12,516 gene families, of which 7663 were gained in the ancestor ofSymbiodinium(Fig. 1Aand table S9). These genes were enriched in 62 metabolic gene ontologies (table S10). When the gene families were normalized tozscores to balance the effect of different total gene numbers, 96 gene families had shrunk (table S11) and 265 gene families had expanded in Symbiodinium(table S12). The LINE-1 reverse transcriptase (a retroelement) is the most highly expanded family.