PLANT PHYSIOLOGY , Vol 113, Issue 3 677-683, Copyright © 1997 by American Society of Plant Biologists
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DEVELOPMENT AND GROWTH REGULATION |
Control of Mitosis by Phytochrome and a Blue-Light Receptor in Fern Spores
M. Furuya, M. Kanno, H. Okamoto, S. Fukuda and M. Wada
Hitachi Advanced Research Laboratory, Hatoyama, Saitama 350-03, Japan (M.F.)
The first mitosis in spores of the fern A. capillus-veneris was observed
under a microscope equipped with Nomarski optics with irradiation from a
safelight at 900 nm, and under a fluorescent microscope after staining with
4[prime],6-diamidino-2-phenylindole. During imbibition the nucleus remained
near one corner of each tetrahedron-shaped dormant spore, and asymmetric
cell division occurred upon brief irradiation with red light. This red
light-induced mitosis was photoreversibly prevented by subsequent brief
exposure to far-red light and was photo-irreversibly prevented by brief
irradiation with blue light. However, neither far-red nor blue light
affected the germination rate when spores were irradiated after the first
mitosis. Therefore, the first mitosis in the spores appears to be the
crucial step for photoinduction of spore germination. Furthermore,
experiments using a microbeam of red or blue light demonstrated that blue
light was effective only when exposed to the nucleus, and no specific
intracellular photoreceptive site for red light was found in the spores.
Therefore, phytochrome in the far-red absorbing form induces the first
mitosis in germinating spores but prevents the subsequent mitosis in
protonemata, whereas a blue-light receptor prevents the former but induces
the latter.
