Inhibition of mitochondrial respiration by the flavone aglycone isovitexin causes aberrant petal and leaf morphology in Silene latifolia.

The morphological mutant "isovitexin" in Silene latifolia (the white campion) has small and up-curled petals and leaves. In this mutant the aglycone isovitexin is the only flavone present in the vacuole. In the present study it is shown that isovitexin has a strong toxic effect on mitochondria that is to a large extent abolished by glycosylation. This effect can be used to explain the aberrant morphology. Isovitexin acts at the level of the ubiquinone pool; cytochrome c - cytochrome aa3 oxidase activity was unaffected, and with either reduced nicotinamide adenine dinucleotide or succinate as a respiratory substrate, effects on respiration were found in Silene leaves-, potato (Solanum tuberosum) tuber- and sweet potato (Ipomoea batata L.) tuber mitochondria. Since in sweet potato electron transport via the cyanide insensitive pathway was also inhibited, with the ubiquinone pool as the only component (besides the dehydrogenases) shared by these two pathways, the site of inhibition must be at this level.