Actin turnover is required for myosin-dependent mitochondrial movements in Arabidopsis root hairs.
BACKGROUND
Previous studies have shown that plant mitochondrial movements are myosin-based along actin filaments, which undergo continuous turnover by the exchange of actin subunits from existing filaments. Although earlier studies revealed that actin filament dynamics are essential for many functions of the actin cytoskeleton, there are little data connecting actin dynamics and mitochondrial movements.


RESULTS
We addressed the role of actin filament dynamics in the control of mitochondrial movements by treating cells with various pharmaceuticals that affect actin filament assembly and disassembly. Confocal microscopy of Arabidopsis thaliana root hairs expressing GFP-FABD2 as an actin filament reporter showed that mitochondrial distribution was in agreement with the arrangement of actin filaments in root hairs at different developmental stages. Analyses of mitochondrial trajectories and instantaneous velocities immediately following pharmacological perturbation of the cytoskeleton using variable-angle evanescent wave microscopy and/or spinning disk confocal microscopy revealed that mitochondrial velocities were regulated by myosin activity and actin filament dynamics. Furthermore, simultaneous visualization of mitochondria and actin filaments suggested that mitochondrial positioning might involve depolymerization of actin filaments on the surface of mitochondria.


CONCLUSIONS
Base on these results we propose a mechanism for the regulation of mitochondrial speed of movements, positioning, and direction of movements that combines the coordinated activity of myosin and the rate of actin turnover, together with microtubule dynamics, which directs the positioning of actin polymerization events.
Zheng
Maozhong
M
Key Laboratory of Photosynthesis and Molecular Environmental Physiology, Institute of Botany, Chinese Academy of Sciences, Beijing, China.
Beck
Martina
M
Müller
Jens
J
Chen
Tong
T
Wang
Xiaohua
X
Wang
Feng
F
Wang
Qinli
Q
Wang
Yuqing
Y
Baluska
Frantisek
F
Logan
David C
DC
Samaj
Jozef
J
Lin
Jinxing
J
D008841:Actin Cytoskeleton / Q000737:chemistry; D000199:Actins / Q000737:chemistry / Q000378:metabolism*; D017360:Arabidopsis / Q000378:metabolism*; D029681:Arabidopsis Proteins / Q000737:chemistry; D003599:Cytoskeleton / Q000378:metabolism; D049452:Green Fluorescent Proteins / Q000737:chemistry; D018613:Microscopy, Confocal / Q000379:methods; D008870:Microtubules / Q000378:metabolism; D008928:Mitochondria / Q000378:metabolism*; D008954:Models, Biological; D015233:Models, Statistical; D009218:Myosins / Q000378:metabolism*; D018517:Plant Roots / Q000502:physiology*; D010957:Plasmids / Q000378:metabolism
D000199:Actins; D029681:Arabidopsis Proteins; D049452:Green Fluorescent Proteins; D009218:Myosins