Journal
PROCEEDINGS OF THE NATIONAL ACADEMY OF SCIENCES OF THE UNITED STATES OF AMERICA
Volume 107, Issue 19, Pages 8860-8865Publisher
NATL ACAD SCIENCES
DOI: 10.1073/pnas.0912773107
Keywords
cp-actin; blue light; organelle movement; phototropin
Categories
Funding
- Japanese Ministry of Education, Sports, Science, and Technology (MEXT) [13139203, 17084006, 19039027]
- Japan Society of Promotion of Science (JSPS) [13304061, 16107002, 20227001, 19570045, 20870030]
- Grants-in-Aid for Scientific Research [13139203, 19570045, 20870030, 13304061, 16107002, 19039027, 20227001] Funding Source: KAKEN
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Organelle movement is essential for efficient cellular function in eukaryotes. Chloroplast photorelocation movement is important for plant survival as well as for efficient photosynthesis. Chloroplast movement generally is actin dependent and mediated by blue light receptor phototropins. In Arabidopsis thaliana, phototropins mediate chloroplast movement by regulating short actin. laments on chloroplasts (cp-actin filaments), and the chloroplast outer envelope protein CHUP1 is necessary for cp-actin. lament accumulation. However, other factors involved in cp-actin. lament regulation during chloroplast movement remain to be determined. Here, we report that two kinesin-like proteins, KAC1 and KAC2, are essential for chloroplasts to move and anchor to the plasma membrane. A kac1 mutant showed severely impaired chloroplast accumulation and slow avoidance movement. A kac1kac2 double mutant completely lacked chloroplast photorelocation movement and showed detachment of chloroplasts from the plasma membrane. KAC motor domains are similar to those of the kinesin-14 subfamily (such as Ncd and Kar3) but do not have detectable microtubule-binding activity. The C-terminal domain of KAC1 could interact with F-actin in vitro. Instead of regulating microtubules, KAC proteins mediate chloroplast movement via cp-actin. laments. We conclude that plants have evolved a unique mechanism to regulate actin-based organelle movement using kinesin-like proteins.
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