Journal Article

Differential Positioning of C<sub>4</sub> Mesophyll and Bundle Sheath Chloroplasts: Recovery of Chloroplast Positioning Requires the Actomyosin System

Hiroaki Kobayashi, Masahiro Yamada, Mitsutaka Taniguchi, Michio Kawasaki, Tatsuo Sugiyama and Hiroshi Miyake

in Plant and Cell Physiology

Published on behalf of Japanese Society of Plant Physiologists

Volume 50, issue 1, pages 129-140
Published in print January 2009 | ISSN: 0032-0781
Published online December 2008 | e-ISSN: 1471-9053 | DOI: http://dx.doi.org/10.1093/pcp/pcn177
Differential Positioning of C4 Mesophyll and Bundle Sheath Chloroplasts: Recovery of Chloroplast Positioning Requires the Actomyosin System

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  • Biochemistry
  • Molecular and Cell Biology
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In C4 plants, bundle sheath (BS) chloroplasts are arranged in the centripetal position or in the centrifugal position, although mesophyll (M) chloroplasts are evenly distributed along cell membranes. To examine the molecular mechanism for the intracellular disposition of these chloroplasts, we observed the distribution of actin filaments in BS and M cells of the C4 plants finger millet (Eleusine coracana) and maize (Zea mays) using immunofluorescence. Fine actin filaments encircled chloroplasts in both cell types, and an actin network was observed adjacent to plasma membranes. The intracellular disposition of both chloroplasts in finger millet was disrupted by centrifugal force but recovered within 2 h in the dark. Actin filaments remained associated with chloroplasts during recovery. We also examined the effects of inhibitors on the rearrangement of chloroplasts. Inhibitors of actin polymerization, myosin-based activities and cytosolic protein synthesis blocked migration of chloroplasts. In contrast, a microtubule-depolymerizing drug had no effect. These results show that C4 plants possess a mechanism for keeping chloroplasts in the home position which is dependent on the actomyosin system and cytosolic protein synthesis but not tubulin or light.

Keywords: Actin filament; C4 photosynthesis; Chloroplast; Eleusine coracana; Zea mays

Journal Article.  6247 words.  Illustrated.

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

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