Regulation of actin-dependent cytoplasmic motility by type II phytochrome occurs within seconds in Vallisneria gigantea epidermal cells.
The effects of light on actin-dependent cytoplasmic motility in epidermal cells of green leaves of the aquatic angiosperm Vallisneria gigantea were investigated quantitatively using a custom-made dynamic image analyzer. Cytoplasmic motility was measured by monitoring changes in the brightness of individual pixels on digitized images taken sequentially under infrared light. Acceleration and deceleration of cytoplasmic motility were regulated photoreversibly by type II phytochrome(s). This phytochrome-dependent induction of cytoplasmic motility did not occur uniformly in cytoplasm but took place as scattered patches in which no particular organelles, including nucleus, existed. The induction became detectable at 2.5 s after the start of irradiation with pulsed red light. In cells exposed to microbeam irradiation, cytoplasmic motility was induced only in sites in the cytoplasm that were irradiated directly, whereas nonirradiated neighboring areas were unaffected. The effect was short-lived, disappearing within a few minutes, and no signal was transmitted from an irradiated cell to its neighbors. Anti-phytochrome antibody-responsive protein(s) was detectable in the leaf extract by immunoblot and zinc blot analyses and in cryosections of the epidermis by immunocytochemistry. Although the phytochrome-dependent cytoplasmic motility was blocked by exogenously applied latrunculin B or cytochalasins, treatment of the dark-adapted cells with Ca(2+)-chelating reagents induced the cytoplasmic motility. We have proposed a model for the phytochrome regulation of cytoplasmic motility as one of the earliest responses to a light stimulus.
Takagi
Shingo
S
Department of Biology, Graduate School of Science, Osaka University, Toyonaka, Osaka 560-0043, Japan. shingot@bio.sci.osaka-u.ac.jp
Kong
Sam-Geun
SG
Mineyuki
Yoshinobu
Y
Furuya
Masaki
M
D008841:Actin Cytoskeleton / Q000502:physiology*; D019086:Bridged Bicyclo Compounds, Heterocyclic / Q000494:pharmacology; D002118:Calcium / Q000378:metabolism; D002614:Chelating Agents / Q000494:pharmacology; D003572:Cytochalasins / Q000494:pharmacology; D003593:Cytoplasm / Q000187:drug effects / Q000502:physiology / Q000528:radiation effects; D003595:Cytoplasmic Streaming / Q000187:drug effects / Q000502:physiology* / Q000528:radiation effects; D003599:Cytoskeleton / Q000187:drug effects / Q000502:physiology / Q000528:radiation effects; D007091:Image Processing, Computer-Assisted; D015151:Immunoblotting; D007150:Immunohistochemistry; D008027:Light; D019684:Magnoliopsida / Q000378:metabolism* / Q000528:radiation effects; D010590:Phalloidine / Q000494:pharmacology; D010834:Phytochrome / Q000378:metabolism*; D019441:Plant Epidermis / Q000378:metabolism* / Q000528:radiation effects; D018515:Plant Leaves / Q000378:metabolism / Q000528:radiation effects; D013844:Thiazoles / Q000494:pharmacology; D053778:Thiazolidines; D013997:Time Factors
D019086:Bridged Bicyclo Compounds, Heterocyclic; D002614:Chelating Agents; D003572:Cytochalasins; D013844:Thiazoles; D053778:Thiazolidines; D010834:Phytochrome; D010590:Phalloidine; C037068:latrunculin B; D002118:Calcium