Zx. Xie et Zx. Chen, Salicylic acid induces rapid inhibition of mitochondrial electron transport and oxidative phosphorylation in tobacco cells, PLANT PHYSL, 120(1), 1999, pp. 217-225
Salicylic acid (SA) is known to induce alternative pathway respiration by a
ctivating expression of the alternative oxidase gene. In the present study
we report a rapid mode of action by SA on plant mitochondrial functions. SA
at concentrations as low as 20 mu M induced inhibition of both ATP synthes
is and respiratory O-2 uptake within minutes of incubation in tobacco (Nico
tiana tabacum) cell cultures. Biologically active SA analogs capable of ind
ucing pathogenesis-related genes and enhanced resistance also caused rapid
inhibition of ATP synthesis and respiratory O-2 uptake, whereas biologicall
y inactive analogs did not. Inhibition of ATP synthesis and respiratory O-2
uptake by SA was insensitive to the protein synthesis inhibitor cyclohexim
ide, but was substantially reduced by the antioxidant N-acetylcysteine, sug
gesting a possible role for reactive oxygen species in the inhibition of mi
tochondrial functions. With exogenous NADH as the respiratory substrate, mi
tochondria isolated from SA-treated tobacco cell cultures were found to hav
e normal capacities for both ATP synthesis and respiratory O-2 uptake; dire
ct incubation of isolated mitochondria with SA had no significant effect on
these mitochondrial functions. These results indicate that (a) the respira
tion capacities of isolated mitochondria do not correspond to the in vivo r
espiration activities in SA-treated cell cultures and (b) the SA-induced in
hibition of respiration in tobacco cell cultures may involve other componen
ts that are not present in isolated mitochondria. Given the recently demons
trated roles of mitochondria in plant disease resistance and animal apoptos
is, this rapid inhibition by SA of mitochondrial functions may play a role
in SA-mediated biological processes, including plant defense responses.