Light irradiation induces fragmentation of the plasmodium, a novel photomorphogenesis in the true slime mold Physarum polycephalum: action spectra and evidence for involvement of the phytochrome.
A new photomorphogenesis was found in the plasmodium of the true slime mold Physarum polycephalum: the plasmodium broke temporarily into equal-sized spherical pieces, each containing about eight nuclei, about 5 h after irradiation with light. Action spectroscopic study showed that UVA, blue and far-red lights were effective, while red light inhibited the far-red-induced fragmentation. Difference absorption spectra of both the living plasmodium and the plasmodial homogenate after alternate irradiation with far-red and red light gave two extremes at 750 and 680 nm, which agreed with those for the induction and inhibition of the fragmentation, respectively. A kinetic model similar to that of phytochrome action explained quantitatively the fluence rate-response curves of the fragmentation. Our results indicate that one of the photoreceptors for the plasmodial fragmentation is a phytochrome.
Kakiuchi
Y
Y
Research Institute for Electronic Science, Hokkaido University, 060-0812 Sapporo, Japan.
Takahashi
T
T
Murakami
A
A
Ueda
T
T
D000818:Animals; D003593:Cytoplasm / Q000528:radiation effects*; D008027:Light; D009024:Morphogenesis; D016839:Physarum polycephalum / Q000254:growth & development / Q000528:radiation effects*; D010834:Phytochrome / Q000502:physiology*
D010834:Phytochrome