生物学教室公開セミナー
日時：2014年7月17日（木）10:00-12:00
場所：早稲田大学50号館
Peculiar photosynthesis of Chromerids
Ondrej Prasil (Institute of Microbiology ASCR, Centrum Algatech, Laboratory of photosynthesis)
Chromerids are new group of algae, closely related to the heterotrophic parasites Apicomplexa (e.g. Plasmodium, Toxoplasma). Since its discovery and initial characterization [1], Chromera velia has achieved interest also for its unusual and unique photosynthetic properties. In my presentation I will summarize results achieved in our laboratory on studies of photosynthesis in Chromera [2,3] and its related, but distinct species Vitrella. Recently we have analysed in depth the response of both strains to different quality of spectral irradiance, showing in detail how Chromera responds to red light by synthesis of a new light harvesting protein (Red-CLH) that increases its fitness in the specific light environment of corals [4,5]. Our data also indicate high mobility of light harvesting antennae in thylakoid membranes of Chromera. This also influences the redistribution (so called spill-over) of absorbed excitation energy among both photosystems. We have also studied the effect of environmental factors on the fatty acid composition in Chromera. Current results on the operation of carbon concentrating mechanism found in chromerids that contain Rubisco - type II will be also briefly discussed. The functional significance of the observed presence of uniquely split proteins for the core of Photosystem I or ATP synthase in Chromera [6] remains still to be understood.
[1] Moore RB, Obornik M, Janouskovec J, Chrudimsky T, Vancova M, Green DH, Wright SW, Davies NW, Bolch CJS, Heimann K, Slapeta J, Hoegh-Guldberg O, Logsdon JM, Carter DA (2008) A photosynthetic alveolate closely related to apicomplexan parasites. Nature 451:959-963.
[2] Kotabova E, Kana R, Jaresova J, Prasil O (2011) Non-photochemical fluorescence quenching in Chromera velia is enabled by fast violaxanthin de-epoxidation. FEBS Letters 585:1941-1945.
[3] Quigg A, Kotabova E, Jaresova J, Kana R, Setlik J, Sediva B, Komarek O, Prasil O (2012) Photosynthesis in Chromera velia Represents a Simple System with High Efficiency. Plos One 7 (10). doi:10.1371/journal.pone.0047036
[4] Kotabova E, Jaresova J, Kana R, Sobotka R, Bina D, Prasil O (2014) Novel type of red-shifted chlorophyll a antenna complex from Chromera velia. I. Physiological relevance and functional connection to photosystems. BBA - Bioenergetics 1837:734-743.
[5] Bina D, Gardian Z, Herbstova M, Kotabova E, Konik P, Litvin R, Prasil O, Tichy J, Vacha F (2014) Novel type of red-shifted chlorophyll a antenna complex from Chromera velia: II. Biochemistry and spectroscopy. BBA - Bioenergetics 1837:802-810.
[6] Janouskovec J, Sobotka R, Lai D-H, Flegontov P, Konik P, Komenda J, Ali S, Prasil O, Pain A, Obornik M, Lukes J, Keeling PJ (2013) Split photosystem protein, linear-mapping topology and growth of structural complexity in the plastid genome of Chromera velia. Mol Biol Evol 30:2447-2462.
プラシル教授を迎えて
プラシル教授とポスドクの増田さんをお迎えしてセミナーを開催しました。聴き手は若い学生がほとんどだったこともあり、丁寧に解説を加えつつ話していただきました。マラリア病原体と近縁な藻類を調べることにより、光合成生物と非光合成生物の間のミッシングリンクが明らかになった感じがします。系Ⅰの反応中心複合体のサブユニットが分断されて転写翻訳されていたり、近赤外光を吸収することができる系２のアンテナが赤外光いよって誘導されたり、「普通の」光合成とは異なるユニークな光合成装置は、モデル生物だけを調べていてはわからない部分でしょう。聴衆は生物学教室から１３名、その他の学内から８名、外部の大学と研究機関から６名でした。