Ozone-induced ethylene and foliar injury responses are altered in 1-aminocyclopropane-1-carboxylate synthase antisense potato plants

In potato (Solanum tuberosum), two 1-aminocyclopropane-1-carboxylate synthase (ACS) genes are induced by ozone (O₃). Antisense inhibition of these ethylene (C₂H₄) biosynthetic genes allowed us to examine the relationship between O₃-induced C₂H ₄ emission and foliar injury. • Thirty-two lines (antisense for ST-ACS4 or ST-ACS5) were screened in the glasshouse for acute O ₃-induced C₂H₄ and lesions. Stomatal conductance and ACS transcripts were quantified for selected C₂H ₄-altered lines. Six lines were field-tested for chronic O ₃ effects. • Ten lines produced less, and four lines produced more, acute-O₃-induced C₂H₄ than nontransformed (NT) plants. Ethylene levels did not appear to be correlated with stomatal conductance. ST-ACS4 and -5 transcript were reduced in transgenic plants, except in two C₂H₄ over-producing lines. In the field, these C₂H₄ over-producing lines displayed stunting and leaf rolling in charcoal-filtered (CF) air and chronic O₃, and they sustained the most severe O₃ injury. • When C₂H ₄ production was strongly suppressed or enhanced, corresponding reductions or increases in lesion severity were observed, suggesting a critical role for C₂H₄ in the lesion formation process during O₃ stress.