Poster Session Theme: Evolution, Biodiversity and Bio-resources

Aki Masunaga, OIST

Genomics and Regulatory Systems Unit

Luscombe Unit

The larvacean Oikopleura dioica is an abundant planktonic tunicate found in all oceans. Together with other larvaceans, O. dioica plays a significant role in vertical carbon flux. Despite its ubiquitous distribution, it is classified as a single species based on simple morphological features. However, high sequence divergence has been observed in three published genomes of O. dioica. We investigated ITS regions in ribosomal DNA genes and found three distinct groups from the North Atlantic, the North Pacific, and the Ryukyu Archipelago. Our mating experiment of two neighboring populations in Japan showed reproductive isolation. Cellular arrangements of species-specific epidermis layer were examined for morphological analysis. In order to better understand the population structures of diecious Oikopleura, the animals were sampled from 10 geographical locations and sequenced using Nanopore MinION platform. Our studies corroborate speciation of the dioecious larvacean model, highlighting their genome plasticity and complexity of population structures. Further investigations are necessary to elucidate larvacean diversity for more species awaiting discovery.

Yuko Makita, RIKEN

Center for Sustainable Resource Science

Synthetic Genomics Research Group

Blue light penetrate deeper into the ocean and blue light sensing is a key to know their environment for organisms. We focused on a blue light photoreceptor of cryptochrome (cry), which is widely distributed in bacteria, fungi, animals and plants, and searched novel cry genes in marine metagenome data. Interestingly, we found a novel chimeric photoreceptor of red-light sensing phytochrome (phy) and cry. To estimate the host organism, we used the Marine Microbial Eukaryote Transcriptome Sequencing Project (MMETSP) dataset and luckily found 100% identity fragment with a marine picoplankton, Pycnococcus provasolii. The photosensing activity was confirmed with UV and visible absorption spectra of phy and cry parts of the chimeric protein. This fused photoreceptor detects light within the orange/far-red and blue spectra and act as a dual photoreceptor and it named as dualchrome (duc). Based on its genome sequence, we predicted five crys, one duc but there is no phy. Transcriptome analysis under monochromatic light condition was also performed.

Yuko Makita1, Shigekatu Suzuki2, Keiji Fushimi3, Setsuko Shimada1, Tomoko Kuriyama1, Yukio Kurihara1, Hidefumi Hamasaki1, Rei Narikawa3, Haruyo Yamaguchi2, Masanobu Kawachi2, Minami Matsui1.

1Synthetic Genomics Research Group, RIKEN Center for Sustainable Resource Science. 2Center for Environmental Biology and Ecosystem Studies, National Institute for Environmental Studies. 3Graduate School of Integrated Science and Technology, Shizuoka University

Maria Alves dos Santos, OIST

Evolution, Cell Biology, and Symbiosis Unit

Husnik Unit

Apicomplexan species cause many diseases such as malaria and toxoplasmosis. Although these parasites evolved from algal ancestors, the transition from the photosynthetic free-living lifestyle to parasitism is poorly understood. Corallicolids are endosymbionts of corals and they are the only apicomplexans that still retain the four plastid genes related to chlorophyll biosynthesis. Unfortunately, there is little information about corallicolid diversity and function. Here, we used Sanger and Illumina sequencing to examine the corallicolid genotypes associated with 12 coral species across Japan, Caribbean, Hawai’i, New Caledonia, Palau, Red Sea, and Taiwan. We then used FISH to confirm the presence of corallicolid cells in coral tissues. Our preliminary results reveal that all corallicolids detected so far from corals in Japan belong to the same lineage. This lineage seems to be a generalist clade associated with different coral hosts and widespread across the globe, while other lineages seem to associate with specific hosts or geographic regions. The results thus provide a baseline for future research on functional genomics of corallicolids.

Maria E. A. Santos1, Kamila K. Kozik1, James D. Reimer2, Filip Husnik1

1Evolution, Cell Biology, and Symbiosis Unit - Okinawa Institute of Science and Technology Graduate University 2Molecular Invertebrate and Systematics Ecology Lab - University of the Ryukyus