Incubation of Petunia hybrida cells with H2O2 leads to an increase in alternative oxidase activity measured after 24 h. This increased activity is accompanied by an increase in alternative oxidase protein. A model is presented for the regulation of alternative oxidase protein synthesis in which active oxygen species and especially H2O2 play a crucial role as second messengers in the signal transducing pathway from the mitochondria to the nucleus. It is proposed that also the induction of the alternative oxidase by salicylic acid is mediated via H2O2.
