Fatty acid omega3 desaturases act on membrane lipids to catalyse the formation of trienoic fatty acids, the most abundant in plant tissues being alpha-linolenic acid. This fatty acid is a precursor of jasmonic acid, a plant growth regulator involved in the control of wound-induced gene activation in plants and in the induction of tuberization in potato. We isolated a potato omega3 desaturase cDNA, possibly encoding a plastidial isoform, and used it to investigate its expression pattern throughout plant development and in response to wounding. Plastidial omega3 desaturase gene transcripts accumulate rapidly upon wounding, preceding the jasmonate-dependent induction of the wound-responsive proteinase inhibitor II gene. We generated transgenic potato plants constitutively expressing an antisense RNA to this plastidial omega3 desaturase. Selected transgenic lines in which the cognate omega3 desaturase mRNA is largely depleted show a marked reduction, of up to 60%, in trienoic acids in leaves and tubers. In these lines, a corresponding reduction in jasmonate content and proteinase inhibitor II expression is observed upon wounding. Our results indicate that a reduction in omega3 desaturase mRNA levels compromises the wound-induced activation of proteinase inhibitor II, suggesting that wound-induced synthesis of linolenic acid is required for jasmonic acid production. The antisense-mediated depletion of fatty acid omega3 desaturases is a viable alternative for reducing trienoic fatty acid content in plant species in which a mutant screening approach is not applicable.