Ozone as a tool for studying stress responses in tomato: Signalling and defence in normal and mutant lines

In the present contribution, a first set of results concerning signalling and defence in tomato mutant lines impaired in ethylene perception (Never ripe) or biosynthesis (ripening inhibitor) after exposure to realistically elevated O-3 as a model stressor, are presented. Differences in terms of temporal activation and relative transcripts abundance of the ethylene biosynthetic enzymes 1-aminocyclopropane-1-carboxylic acid (ACC) synthase and ACC oxidase, as well as of the ethylene receptor NR, were observed among the two aforementioned mutants and their common near isogenic wild type. Since the three genotypes compared were equally damaged by the treatment, a sort of isoform "compensation" among ethylene biosynthetic genes could be hypothesised, with the common aim of producing an ethylene burst triggering defence responses. Such a burst was indeed observed and showed similar time patterns in the three genotypes, although the peak ethylene emission levels were different.