title: Short actin-based mechanism for light-directed chloroplast movement in Arabidopsis.
abstract: Organelle movement is essential for proper function of living cells. In plants, these movements generally depend on actin filaments, but the underlying mechanism is unknown. Here, in Arabidopsis, we identify associations of short actin filaments along the chloroplast periphery on the plasma membrane side associated with chloroplast photorelocation and anchoring to the plasma membrane. We have termed these chloroplast-actin filaments (cp-actin filaments). Cp-actin filaments emerge from the chloroplast edge and exhibit rapid turnover. The presence of cp-actin filaments depends on an actin-binding protein, chloroplast unusual positioning1 (CHUP1), localized on the chloroplast envelope. chup1 mutant lacked cp-actin filaments but showed normal cytoplasmic actin filaments. When irradiated with blue light to induce chloroplast movement, cp-actin filaments relocalize to the leading edge of chloroplasts before and during photorelocation and are regulated by 2 phototropins, phot1 and phot2. Our findings suggest that plants evolved a unique actin-based mechanism for organelle movement.
authors.affiliation: Department of Biological Sciences, Graduate School of Science and Engineering, Tokyo Metropolitan University, Tokyo 192-0397, Japan. kadota@tmu.ac.jp
authors.forename: Akeo
authors.initials: A
authors.lastname: Kadota
authors.forename: Noboru
authors.initials: N
authors.lastname: Yamada
authors.forename: Noriyuki
authors.initials: N
authors.lastname: Suetsugu
authors.forename: Mana
authors.initials: M
authors.lastname: Hirose
authors.forename: Chieko
authors.initials: C
authors.lastname: Saito
authors.forename: Keiko
authors.initials: K
authors.lastname: Shoda
authors.forename: Satoshi
authors.initials: S
authors.lastname: Ichikawa
authors.forename: Takatoshi
authors.initials: T
authors.lastname: Kagawa
authors.forename: Akihiko
authors.initials: A
authors.lastname: Nakano
authors.forename: Masamitsu
authors.initials: M
authors.lastname: Wada
mesh_terms: D000199:Actins / Q000502:physiology*; D017360:Arabidopsis / Q000502:physiology*; D029681:Arabidopsis Proteins / Q000502:physiology; D002462:Cell Membrane / Q000737:chemistry; D060365:Chloroplast Proteins; D002736:Chloroplasts / Q000502:physiology*; D056931:Cryptochromes; D005420:Flavoproteins / Q000502:physiology; D005453:Fluorescence; D049452:Green Fluorescent Proteins; D008027:Light; D008840:Microfilament Proteins / Q000502:physiology; D008870:Microtubules / Q000502:physiology; D009068:Movement
chemical_list: D000199:Actins; D029681:Arabidopsis Proteins; C538962:CRY1 protein, Arabidopsis; D060365:Chloroplast Proteins; D056931:Cryptochromes; D005420:Flavoproteins; D008840:Microfilament Proteins; C483724:chloroplast unusual positioning1 protein, Arabidopsis; D049452:Green Fluorescent Proteins