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 (O-3). Antisense inhibition of these ethylene (C2H4) biosynthetic genes allowed us to examine the relationship between O-3-induced C2H4 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 C2H4-altered lines. Six lines were field-tested for chronic O-3 effects. Ten lines produced less, and four lines produced more, acute-O-3-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 O-3, and they sustained the most severe O-3 injury. When C2H4 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 O-3 stress.