Plant mitochondrial dynamics
Peroxisome
Chloroplast
Nucleus
Mitochondria
from Alberts et al. 1994
Living Arabidopsis leaf
10 µm
Logan & Leaver (2000) Journal of Experimental Botany, 51: 865-871
5 µm
S. cerevisiae with GFP-targeted to the mitochondrial matrix
Egner, Jakobs, Hell (2002) Proc Natl Acad Sci USA 99: 3370-3375
Copyright ©2002 by the National Academy of Scieces
The mammalian chondriome is often organised into reticula
Youle & Karbowski (2005) Nature Reviews Molecular Cell Biology 6: 657-663
Movie courtesy of Richard Youle
Dnm1p and Fzo1p act in opposing fission and fusion pathways
to maintain the yeast reticular chondriome
Mozdy, McCaffery, Shaw (2000) Journal of Cell Biology 151: 367-380
© The Rockefeller University Press
Mitochondrial division apparatus in Saccharomyces cerevisiae
Okamoto & Shaw (2005) Annual Review of Genetics 39: 503-536
© 2005 Annual Reviews
Mitochondrial division apparatus in Saccharomyces cerevisiae
DRP3A/B
DRP3A & B
BIGYIN
BIGYIN
?
Chondriome structure in Arabidopsis
Arabidopsis abaxial epidermis
Methodology for mutant screen
Arabidopsis expressing GFP targeted to the
mitochondrion
EMS mutagenesis of seed
Screen M2 generation for mitochondrial mutants
using epifluorescence microscopy
Meet the
mutants
Logan et al. (2003) The Plant Journal 36: 500-509
Logan et al. (2003) The Plant Journal 36: 500-509
Logan et al. (2003) The Plant Journal 36: 500-509
The network mitochondria mutant
wild type
10 µm
NETWORK localises to the outer mitochondrial membrane
mito-mCherry
(matrix)
NMT-GFP
(outer membrane)
NETWORK localises to the outer mitochondrial membrane
Mitochondrial division apparatus in Saccharomyces cerevisiae
DRP3A/B
DRP3A & B
BIGYIN
BIGYIN
NMT?
Okamoto & Shaw (2005) Annual Review of Genetics 39: 503-536
© 2005 Annual Reviews
Mitochondrial division apparatuses
Mitochondrial fusion apparatuses
The friendly mitochondria mutant
Logan et al. (2003) The Plant Journal 36: 500-509
The friendly mitochondria mutant
wt
friendly
10µm
wt
1µm
10µm
friendly
1µm
Logan et al. (2003) The Plant Journal 36: 500-509
FRIENDLY - a conserved CLU-type protein
friendly
wild type
Mitochondria in wild type and in friendly move on actin
friendly
Mitochondria in wild type and in friendly move on actin
+ 2 µM latrunculin B to depolymerise actin
Actin dynamics disrupt clusters in friendly
Watch a
cluster build
until it is
disrupted at
+60s.
Clusters do not move on microtubules
Mitochondria (green)
and microtubules (red)
Treated with oryzalin
to depolymerise
microtubules
clueless, the FRIENDLY orthologue in Drosophila has been genetically
implicated in mitochondrial quality control
Cox RT & Spradling AC (2009) Disease Models and Mechanisms. 2:
490-499
Clusters do not associate with MT plus ends
Mitochondria (green)
and EB1b (red)
FRIENDLY-GFP associates with mitochondria
Mitochondria - cyan; FRIENDLY-GFP - magenta
How do clusters form?
What about fusion?
•
Mitochondria must meet before they can fuse
!
•
Mitochondria meet by moving on actin
!
•
Mitochondrial association time is increased in friendly
Membrane potential pulsing
Membrane potential pulsing is increased in friendly
Hypothesised to be due to formation of a fusion pore
Exchange of matrix content is increased in friendly
But fusion is not panmictic in clusters
Fusion
•
Required for mitochondrial homeostasis
!
•
Complementation.
!
•
Mitochondrial quality control?
Whole organism growth defects
Increased cell death
Increased autophagy
A role in innate immunity?
Conclusions
•
FRIENDLY is required to regulate the length of time
mitochondria interact.
•
The time taken to interact, and/or the ability of mitochondria to
freely interact with each other, is important for mitochondrial, cell
and plant health. •
FRIENDLY is implicated in mitochondrial quality control.
•
Fusion - first gene identified as being involved in plant
mitochondrial fusion.
•
Clear role of mitochondrial dynamics in the maintenance of
mitochondrial, cell and plant health.
Acknowledgements
Amr M. El-Zawily
Department of Biology
University of Saskatchewan
Canada
Markus Schwarzlander
Institute of Crop Science and Resource
Conservation, University of Bonn, 53113 Bonn,
GERMANY