[PhD Thesis Presentation_Zoom] - Mr. Kun-Lung Li - "A Study of Horizontally Transferred Glycosyl Hydrolase Family 6 Genes in Tunicate Genomes"


Friday, August 20, 2021 - 14:00 to 15:00


Presenter: Mr. Kun-Lung Li

Supervisor: Prof. Hiroshi Watanabe

Co-supervisor: Prof. Noriyuki Satoh

Unit: Evolutionary Neurobiology Unit


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Title: A Study of Horizontally Transferred Glycosyl Hydrolase Family 6 Genes in Tunicate Genomes



Tunicates are the closest extant relatives of vertebrates. Tunicates produce cellulose-containing tunic and exhibit very different lifestyles among animals. Their unique ability to synthesize cellulose results from a horizontally transferred cellulose synthase gene (CesA). Interestingly, a Glycosyl Hydrolase Family 6 (GH6) hydrolase-like domain exists at the C-terminus of tunicate CesA but not in cellulose synthases of other organisms. This led to the identification of another independent GH6-encoding gene, GH6-1, in tunicate genomes. These GH6-encoding genes exist exclusively in tunicates within the animal kingdom. The existence of GH6-encoding genes and the combination of a GH6 and a cellulose synthase domain in tunicate genomes raised the question of the evolutionary origin and function of GH6s in tunicates. To answer these questions, I first examined the phylogenetic relationship of GH6-encoding genes by comparing their sequence signatures. Secondly, I examined the expression of tunicate CesA and GH6-1 genes in Ciona intestinalis type A, a model ascidian tunicate. The gene expression in embryos at early developmental stages was examined by quantitative reverse transcription PCR and in situ hybridization. The results were also compared with a set of single-cell transcriptome data provided by our collaborators. Finally, I generated GH6-1 knockout larvae of C. intestinalis type A to observe the phenotypes of function-less larvae. This study would help to address how tunicates evolved by obtaining their unique anatomy and ecology.

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