In eukaryotes the presence of the dimeric phospholipid cardiolipin (CL) is limited
to the mitochondrial membranes. It resides predominantly in the inner membrane
where it interacts with components of the mitochondrial electron transfer chain. CL
deficiency has previously been shown to affect abundances of the plant NADHdehydrogenase
complex and its association with dimeric cyctochrome c reductase.
Using an Arabidopsis thaliana knock-out mutant for the final enzyme of CL biosynthesis
we here extend current knowledge on the dependence of plant respiration on CL. By
correlating respiratory enzyme abundances with enzymatic capacities in mitochondria
isolated from wild type, CL deficient and CL complemented heterotrophic cell culture
lines a new picture of the participation of CL in plant respiration is emerging.
Data indicate a loss of a general reduction of respiratory capacity in CL deficient
mitochondria which cannot solely be attributed to decreased abundances or capacities
of mitochondrial electron transfer protein complexes and supercomplexes. Instead,
it most likely is the result of a loss of the mobile electron carrier cytochrome c.
Furthermore, enzymes of the tricarboxylic acid cycle are found to have lower maximum
activities in the mutant, including the succinate dehydrogenase complex. Interestingly,
abundance of the latter is not altered, indicative of a direct impact of CL deficiency on
the enzymatic capacity of this electron transfer chain protein complex