TY - JOUR TI - Metabolic co-dependence drives the evolutionarily ancient Hydra–Chlorella symbiosis AU - Hamada, Mayuko AU - Schröder, Katja AU - Bathia, Jay AU - Kürn, Ulrich AU - Fraune, Sebastian AU - Khalturina, Mariia AU - Khalturin, Konstantin AU - Shinzato, Chuya AU - Satoh, Nori AU - Bosch, Thomas CG A2 - Falkowski, Paul G VL - 7 PY - 2018 DA - 2018/05/31 SP - e35122 C1 - eLife 2018;7:e35122 DO - 10.7554/eLife.35122 UR - https://doi.org/10.7554/eLife.35122 AB - 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. KW - Hydra KW - Chlorella KW - symbiosis KW - genome KW - nitrogen metabolism JF - eLife SN - 2050-084X PB - eLife Sciences Publications, Ltd ER -