Expression of the Arabidopsisabi1–1mutant allele inhibits proteinase inhibitor wound-induction in tomato


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Abscisic acid (ABA) is an essential component in the wound signalling cascade. Increased levels of endogenous ABA were observed after wounding and shown to be a requisite for wound-induced expression of the proteinase inhibitor II genes. We have taken advantage of the dominant character of the Arabidopsisabi1–1mutation, to investigate whether ABI1 has a function in ABA signalling in response to wounding. Transgenic tomato plants carrying copies of either the wild-typeABI1or the mutantabi1–1alleles were obtained and assayed for wound-induction of thepin2orLAPgenes. While normal levels of gene induction were observed in the transgenicABI1plants, theabi1–1transformants displayed a severe wilty phenotype and reduced seed dormancy. Expression of theabi1–1dominant mutation blocked accumulation of the drought-inducedTAS14andLE25mRNAs in response to ABA, as well as ABA- and wound-induced expression of the defense-associatedpin2andLAPtranscripts. MeJA-induction of thepin2andLAPmRNAs, on the contrary, was not affected in theabi1–1transformants. These results indicate thatabi1–1inhibits wound-induced expression of thepin2andLAPtranscripts by blocking ABA-induction of these genes. This implicates ABI1 in wound-signalling and suggests that a common early ABA signalling pathway may function in the responses to wounding and water stress.