GENERAL ROLES OF ABSCISIC AND JASMONIC ACIDS IN GENE ACTIVATION AS A RESULT OF MECHANICAL WOUNDING

Exogenous application of abscisic acid (ABA) has been shown to induce a systemic pattern of proteinase inhibitor II (pin2) MRNA accumulation identical to that induced by mechanical wounding. Evidence is presented that the ABA-specific response is not restricted to pin2 genes but appears to be part of a genera reaction to wound stress. Four other wound-induced, ABA-responsive genes that encode two additional proteinase inhibitors, the proteolytic enzyme leucine aminopeptidase, and the biosynthetic enzyme threonine deaminase were isolated from potato plants. Wounding or treatment with ABA resulted in a pattern of accumulation of these mRNAs very similar to that of pin2. ABA-deficient plants did not accumulate any of the mRNAs upon wounding, although they showed normal levels of expression upon ABA treatment. Also, application of methyl jasmonate (MeJA) induced a strong accumulation of these transcripts, both in wild-type and in ABA-deficient plants, thus supporting a role for jasmonic acid as an intermediate in the signaling pathway that leads from ABA accumulation in response to wounding to the transcriptional activation of the genes.