Light-Induced Movements of Chloroplasts and Nuclei Are Regulated in Both Cp-Actin-Filament-Dependent and -Independent Manners in Arabidopsis thaliana.
Light-induced chloroplast movement and attachment to the plasma membrane are dependent on actin filaments. In Arabidopsis thaliana, the short actin filaments on the chloroplast envelope, cp-actin filaments, are essential for chloroplast movement and positioning. Furthermore, cp-actin-filament-mediated chloroplast movement is necessary for the strong-light-induced nuclear avoidance response. The proteins CHLOROPLAST UNUSUAL POSITIONING 1 (CHUP1), KINESIN-LIKE PROTEIN FOR ACTIN-BASED CHLOROPLAST MOVEMENT 1 (KAC1) and KAC2 are required for the generation and/or maintenance of cp-actin filaments in Arabidopsis. In land plants, CHUP1 and KAC family proteins play pivotal roles in the proper movement of chloroplasts and their attachment to the plasma membrane. Here, we report similar but distinct phenotypes in chloroplast and nuclear photorelocation movements between chup1 and kac1kac2 mutants. Measurement of chloroplast photorelocation movement indicated that kac1kac2, but not chup1, exhibited a clear strong-light-induced increase in leaf transmittance changes. The chloroplast movement in kac1kac2 depended on phototropin 2, CHUP1 and two other regulators for cp-actin filaments, PLASTID MOVEMENT IMPAIRED 1 and THRUMIN 1. Furthermore, kac1kac2 retained a weak but significant nuclear avoidance response although chup1 displayed a severe defect in the nuclear avoidance response. The kac1kac2chup1 triple mutant was completely defective in both chloroplast and nuclear avoidance responses. These results indicate that CHUP1 and the KACs function somewhat independently, but interdependently mediate both chloroplast and nuclear photorelocation movements.
Department of Biology, Faculty of Sciences, Kyushu University, Fukuoka, Japan.
Noriyuki
N
Suetsugu
Department of Biology, Faculty of Sciences, Kyushu University, Fukuoka, Japan.
Takeshi
T
Higa
Department of Agriculture, Kyushu University, Fukuoka, Japan.
Eiji
E
Gotoh
Department of Biology, Faculty of Sciences, Kyushu University, Fukuoka, Japan.
Masamitsu
http://orcid.org/0000-0001-6672-7411
M
Wada
D008841:Actin Cytoskeleton / Q000378:metabolism / Q000528:radiation effects / Q000648:ultrastructure; D017360:Arabidopsis / Q000235:genetics / Q000378:metabolism / Q000528:radiation effects* / Q000648:ultrastructure; D029681:Arabidopsis Proteins / Q000235:genetics* / Q000378:metabolism; D002462:Cell Membrane / Q000378:metabolism / Q000528:radiation effects / Q000648:ultrastructure; D002467:Cell Nucleus / Q000378:metabolism / Q000528:radiation effects* / Q000648:ultrastructure; D060365:Chloroplast Proteins / Q000235:genetics* / Q000378:metabolism; D002736:Chloroplasts / Q000378:metabolism / Q000528:radiation effects* / Q000648:ultrastructure; D018506:Gene Expression Regulation, Plant; D047908:Intracellular Signaling Peptides and Proteins / Q000235:genetics / Q000378:metabolism; D016547:Kinesins / Q000235:genetics* / Q000378:metabolism; D008027:Light; D008840:Microfilament Proteins / Q000235:genetics* / Q000378:metabolism; D009068:Movement; D056949:Phototropins / Q000235:genetics / Q000378:metabolism; D059828:Plant Cells / Q000378:metabolism / Q000528:radiation effects / Q000648:ultrastructure; D018515:Plant Leaves / Q000235:genetics / Q000378:metabolism / Q000528:radiation effects / Q000648:ultrastructure
D029681:Arabidopsis Proteins; D060365:Chloroplast Proteins; D047908:Intracellular Signaling Peptides and Proteins; D008840:Microfilament Proteins; D056949:Phototropins; C507141:Pmi1 protein, Arabidopsis; C558162:THRUMIN1 protein, Arabidopsis; C483724:chloroplast unusual positioning1 protein, Arabidopsis; C549626:KAC1 protein, Arabidopsis; C549627:KAC2 protein, Arabidopsis; D016547:Kinesins