Function and evolutionary origin of unicellular camera-type eye structure.
The ocelloid is an extraordinary eyespot organelle found only in the dinoflagellate family Warnowiaceae. It contains retina- and lens-like structures called the retinal body and the hyalosome. The ocelloid has been an evolutionary enigma because of its remarkable resemblance to the multicellular camera-type eye. To determine if the ocelloid is functionally photoreceptive, we investigated the warnowiid dinoflagellate Erythropsidinium. Here, we show that the morphology of the retinal body changed depending on different illumination conditions and the hyalosome manifests the refractile nature. Identifying a rhodopsin gene fragment in Erythropsidinium ESTs that is expressed in the retinal body by in situ hybridization, we also show that ocelloids are actually light sensitive photoreceptors. The rhodopsin gene identified is most closely related to bacterial rhodopsins. Taken together, we suggest that the ocelloid is an intracellular camera-type eye, which might be originated from endosymbiotic origin.
CIB-DDBJ, National Institute of Genetics, Mishima, Japan.
Shiho
S
Hayakawa
CIB-DDBJ, National Institute of Genetics, Mishima, Japan.
Yasuharu
Y
Takaku
CIB-DDBJ, National Institute of Genetics, Mishima, Japan.
Jung Shan
JS
Hwang
Department of Natural History Sciences, Faculty of Science, Hokkaido University, Sapporo, Japan.
Takeo
T
Horiguchi
Department of Cell Biology Biozentrum, University of Basel, Basel, Switzerland.
Hiroshi
H
Suga
Department of Cell Biology Biozentrum, University of Basel, Basel, Switzerland.
Walter
W
Gehring
CIB-DDBJ, National Institute of Genetics, Mishima, Japan.
Kazuho
K
Ikeo
CIB-DDBJ, National Institute of Genetics, Mishima, Japan; Department of Life Sciences, National Cheng Kung University, Tainan, Taiwan; CBRC/BESE, KAUST, Thuwal, 23955-6900, Kingdom of Saudi Arabia.
Takashi
T
Gojobori
D000825:Animal Structures / Q000502:physiology* / Q000528:radiation effects / Q000648:ultrastructure; D000818:Animals; D005075:Biological Evolution; D004141:Dinoflagellida / Q000145:classification / Q000502:physiology* / Q000528:radiation effects / Q000648:ultrastructure; D015870:Gene Expression; D017403:In Situ Hybridization; D007908:Lens, Crystalline / Q000502:physiology* / Q000528:radiation effects / Q000648:ultrastructure; D008027:Light; D010775:Photic Stimulation; D010786:Photoreceptor Cells / Q000502:physiology* / Q000528:radiation effects / Q000648:ultrastructure; D010802:Phylogeny; D015800:Protozoan Proteins / Q000235:genetics / Q000378:metabolism*; D012243:Rhodopsin / Q000235:genetics / Q000378:metabolism*; D025604:Rhodopsins, Microbial / Q000235:genetics / Q000378:metabolism; D017386:Sequence Homology, Amino Acid; D013559:Symbiosis / Q000502:physiology
D015800:Protozoan Proteins; D025604:Rhodopsins, Microbial; D012243:Rhodopsin