Primary stages in photosignal transduction leading to step-up photophobic response in the unicellular eukaryote Blepharisma japonicum.
In order to elucidate the primary stage in the blepharismin phototransduction pathway, changes in the molecular structure of light-exposed blepharismins and oxyblepharismins, were examined. When exposed to light, blepharismins (pink form) were converted into oxyblepharismins (blue form) or dissociated into stentorins/p-hydroxybenzaldehyde with an O2-requiring process, whereas light-exposed oxyblepharismins were not dissociated into stentorins/p-hydroxybenzaldehyde. Since both blepharismins and oxyblepharismins can activate the phototransduction chain leading to the step-up photophobic response presumably through the same pathway, dissociation of p-hydroxybenzaldehyde may not be involved in signal transduction. The fact that the step-up photophobic response requires O2, and both blepharismins and oxyblepharismins produce hydroxyl (OH) radicals probably derived from O2 implies that OH radicals may activate the photosignalling pathway. The step-up photophobic response was not suppressed by a spin trapping reagent for hydroxyl radicals. Other possible primary responses leading to the step-up photophobic response are discussed.
Kida
A
A
Department of Biology, Kochi University, Japan.
Takada
Y
Y
Kotsuki
H
H
Tokumori
D
D
Checcucci
G
G
Matsuoka
T
T
D000818:Animals; D001547:Benzaldehydes / Q000737:chemistry; D016798:Ciliophora / Q000737:chemistry / Q000528:radiation effects*; D008027:Light; D008968:Molecular Conformation; D010100:Oxygen; D010569:Perylene / Q000031:analogs & derivatives* / Q000737:chemistry; D010860:Pigments, Biological / Q000737:chemistry; D015398:Signal Transduction
D001547:Benzaldehydes; D010860:Pigments, Biological; C092293:blepharismin; D010569:Perylene; C011483:4-hydroxybenzaldehyde; D010100:Oxygen