Journal
PLANT AND CELL PHYSIOLOGY
Volume 52, Issue 11, Pages 1973-1982Publisher
OXFORD UNIV PRESS
DOI: 10.1093/pcp/pcr130
Keywords
Actin cytoskeleton; Calcium; Calmodulin; Chloroplast; Chloroplast anchoring; Cortical cytoplasm; Plasma membrane ghost
Categories
Funding
- Japanese Ministry of Education, Culture, Sports, Science and Technology [19039020, 20570037]
- Grants-in-Aid for Scientific Research [19039020, 20570037, 23657035] Funding Source: KAKEN
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Chloroplasts are actively anchored at the appropriate intracellular regions to maintain advantageous distribution patterns under specific environmental conditions. Redistribution of chloroplasts is accompanied by their de-anchoring and re-anchoring, respectively, from and to the cortical cytoplasm. In spinach mesophyll cells, high-intensity blue light and Ca2+ treatment induced the disappearance of the meshwork-like array of actin filaments surrounding chloroplasts, which was suppressed by a calmodulin antagonist. Regulatory mechanisms of chloroplast anchoring were investigated using plasma membrane (PM) ghosts, on which the cortical cytoplasm underlying the PM was exposed. Addition of an actin-depolymerizing reagent or > 1 mu M Ca2+ induced detachment of a substantial number of chloroplasts from the PM ghosts concomitant with disordered actin organization. Calmodulin antagonists and anti-calmodulin antibodies negated the effects of Ca2+. In addition, Ca2+-induced detachment of chloroplasts was no longer evident on the calmodulin-depleted PM ghosts. We propose that chloroplasts are anchored onto the cortical cytoplasm through interaction with the actin cytoskeleton, and that Ca2+-calmodulin-sensitized de-anchoring of chloroplasts is a critical early step in chloroplast redistribution induced by environmental stimuli.
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