Jasmonate signalling can be uncoupled from abscisic acid signalling in barley: identification of jasmonate-regulated transcripts which are not induced by abscisic acid.

Jasmonate and abscisic acid induce several identical mRNAs and proteins in barley. In order to study whether both hormones act through the same signalling pathway, we identified four transcripts induced by jasmonic acid methylester (JM) in leaf segments of barley (Hordeum vulgare L. cv. Salome). These newly identified transcripts were not induced by abscisic acid within the tested times of 2-72 h. This finding supports the conclusion that jasmonate signalling in barley is independent of abscisic acid, in contrast to the wound-induction signal cascade of proteinase-inhibitor II in tomato and potato. Of the four isolated cDNAs, the putative translation frame of one was homologous to caffeic acid methyltransferase, another was homologous to chalcone synthase, and the C-terminus of the third showed homology to two proteins from rice (a salt-induced protein and a root-specific protein); the last cDNA was not homologous to any sequences in the databases. The new cDNAs will be valuable tools for studying jasmonate signal transduction in barley.