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 (C2 H4 ) biosynthetic genes allowed us to examine the relationship between O3 -induced C2 H4 emission and foliar injury. •  Thirty-two lines (antisense for ST-ACS4 or ST-ACS5) were screened in the glasshouse for acute O3 -induced C2 H4 and lesions. Stomatal conductance and ACS transcripts were quantified for selected C2 H4 -altered lines. Six lines were field-tested for chronic O3 effects. •  Ten lines produced less, and four lines produced more, acute-O3 -induced C2 H4 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 C2 H4 over-producing lines. In the field, these C2 H4 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 C2 H4 production was strongly suppressed or enhanced, corresponding reductions or increases in lesion severity were observed, suggesting a critical role for C2 H4 in the lesion formation process during O3 stress.