Modifying alternative respiratory pathway capacity affects chemical induction of resistance to tobacco mosaic virus (TMV) in inoculated leaves. TMV coat protein (CP) accumulation examined 72 hours post-inoculation by immunoblotting using anti-TMV CP serum. Leaves of non-transgenic N. benthamiana plants, plants transformed with an 'empty' transformation vector (Control), or T2 generation transformed plants expressing wild-type AOX (AOX1) or mutant AOX-E (AOX-E3) transgenes were infiltrated with solutions of salicylic acid (SA), antimycin A (AA), or water (W) containing 0.05% (v/v) ethanol (equivalent to the ethanol used to dissolve SA and AA before dilution). Within 10 min of infiltration, leaves were inoculated with TMV (0.05 μg/ml in water). Arrows denote transgenic lines with increased (↑) or decreased (↓) alternative respiratory pathway (AP) capacities. A. Induction of resistance to TMV by AA (2 μM) in directly inoculated leaf tissue was inhibited in plants with increased AP capacity. However, induction of resistance to TMV by SA (2.5 mM) in directly inoculated leaf tissue was not appreciably inhibited in plants with an increased AP capacity. B. A concentration of SA (0.5 mM) that was insufficient to induce resistance in non-transgenic leaves did induce resistance in plants with decreased AP capacity (line AOX-E3). AA at 2 μM was sufficient to induce resistance in non-transgenic leaves and in plants with decreased AP capacity, but insufficient to do so in plants with increased AP capacity. Equal loading of lanes indicated by accumulation of ribulose-1, 5-bisphosphate carboxylase/oxygenase large subunit (LSU) was revealed by Ponceau S staining of immunoblot membranes.