Marine Genomics Unit, Okinawa Institute of Science and Technology Graduate University, Okinawa, Japan; Ushimado Marine Institute, Okayama University, Okayama, Japan
Interdisciplinary Research Center, Kiel Life Science, Kiel University, Kiel, Germany; Zoological Institute, Kiel Life Science, Kiel University, Kiel, Germany
Jay Bathia
Interdisciplinary Research Center, Kiel Life Science, Kiel University, Kiel, Germany; Zoological Institute, Kiel Life Science, Kiel University, Kiel, Germany
Ulrich Kürn
Interdisciplinary Research Center, Kiel Life Science, Kiel University, Kiel, Germany; Zoological Institute, Kiel Life Science, Kiel University, Kiel, Germany
Interdisciplinary Research Center, Kiel Life Science, Kiel University, Kiel, Germany; Zoological Institute, Kiel Life Science, Kiel University, Kiel, Germany
Mariia Khalturina
Marine Genomics Unit, Okinawa Institute of Science and Technology Graduate University, Okinawa, Japan
Marine Genomics Unit, Okinawa Institute of Science and Technology Graduate University, Okinawa, Japan; Atmosphere and Ocean Research Institute, The University of Tokyo, Tokyo, Japan
Interdisciplinary Research Center, Kiel Life Science, Kiel University, Kiel, Germany; Zoological Institute, Kiel Life Science, Kiel University, Kiel, Germany
Many multicellular organisms rely on symbiotic associations for support of metabolic activity, protection, or energy. Understanding the mechanisms involved in controlling such interactions remains a major challenge. In an unbiased approach we identified key players that control the symbiosis between Hydra viridissima and its photosynthetic symbiont Chlorella sp. A99. We discovered significant up-regulation of Hydra genes encoding a phosphate transporter and glutamine synthetase suggesting regulated nutrition supply between host and symbionts. Interestingly, supplementing the medium with glutamine temporarily supports in vitro growth of the otherwise obligate symbiotic Chlorella, indicating loss of autonomy and dependence on the host. Genome sequencing of Chlorella sp. A99 revealed a large number of amino acid transporters and a degenerated nitrate assimilation pathway, presumably as consequence of the adaptation to the host environment. Our observations portray ancient symbiotic interactions as a codependent partnership in which exchange of nutrients appears to be the primary driving force.
