ATP synthesis inhibitors as well as respiratory inhibitors increase steady-state level of alternative oxidase mRNA in Arabidopsis thaliana

The oxygen uptake in mitochondria can be uncoupled from ATP synthesis by the product of a single gene, the alternative oxidase (AOX) gene, which may be involved in signal transduction from mitochondria to the nucleus. To better understand induction of this gene in higher plants, we investigated the effects of the cytochrome respiratory inhibitors and ATP synthesis inhibitors on the expression of the AOXs of Arabidopsis thaliana. A Northern blot analysis showed the AOXla transcripts were increased by treatment of antimycin A and myxothiazol, which act on complex III of the respiratory chain, and by NAN₃, which acts on complex IV. AOX1a mRNA was also strongly induced by oligomycin (F₁F₀-ATP synthase inhibitor) and weakly induced by 2,4-DNP (ATP synthesis uncoupler) at the maximum dose. These results indicate that not only inhibition of electron transfer but also inhibition of ATP synthesis in mitochondria induces the transcription of AOX1a.