Journal Article

Blue Light-Induced Branching in <i>Vaucheria</i>. Requirement of Nuclear Accumulation in the Irradiated Region

Fumio Takahashi, Tasuku Hishinuma and Hironao Kataoka

in Plant and Cell Physiology

Published on behalf of Japanese Society of Plant Physiologists

Volume 42, issue 3, pages 274-285
Published in print March 2001 | ISSN: 0032-0781
Published online March 2001 | e-ISSN: 1471-9053 | DOI: http://dx.doi.org/10.1093/pcp/pce033
Blue Light-Induced Branching in Vaucheria. Requirement of Nuclear Accumulation in the Irradiated Region

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When a narrow region of the fresh water coenocytic alga, Vaucheria terrestris sensu Götz is irradiated with moderately intense blue light, a branch is induced from the center of the irradiated region after 4–5 h. Movement of organelles and microtubule bundles during the photocytomorphogenetic response were investigated. Chloroplasts in the cortical layer immediately started to accumulate in the blue light-irradiated region and their accumulation almost completely finished 30–40 min after the onset of light when the nuclei residing in endoplasm started to accumulate. Accumulation of nuclei was synchronized with disorientation and shortening of microtubule bundles, which originally run parallel to the cell axis. Not only amiprophos-methyl, a potent microtubule-decomposing reagent, but also cytochalasin A strongly inhibited the branch induction. Amiprophos-methyl completely and cytochalasin A mostly destroyed microtubules and completely inhibited nuclear accumulation, but both drugs allowed the accumulation of chloroplasts in the cortical layer of irradiated region. These indicate that the accumulation of nuclei is indispensable for branch induction while the chloroplast accumulation is insufficient by itself for branch induction. The ineffectiveness of cytochalasin A on chloroplast movement brings the conventional view of sliding movement of chloroplast on a long actin cable into question. The morphological and functional relationship between a nucleus and a microtubular bundle are discussed.

Keywords: Key words: Blue light — Branch induction — Coenocytes — Microtubules — Nuclear movement — Vaucheria (Stramenopile).; Abbreviations: APM, amiprophos methyl, N-isopropyl O-methyl O-(2-nitro-p-tolyl) phosphoramidothioate; BL, blue light; BSA, bovine serum albumin; CA, cytochalasin A; DAPI, 4′,6′-diamidino-2-phenylindole dihydrochloride; DMSO, dimethylsulfoxide; FITC, fluorescein isothiocyanate; PBS, phosphate-buffered saline; PIPES, piperazine-1,4-bis(2-ethanesulfonic acid); MT, microtubule.

Journal Article.  8015 words.  Illustrated.

Subjects: Biochemistry ; Molecular and Cell Biology ; Plant Sciences and Forestry

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