IDENTIFICATION OF A METHYL JASMONATE-RESPONSIVE REGION IN THE PROMOTER OF A LIPOXYGENASE-1 GENE EXPRESSED IN BARLEY-GRAIN

A genomic DNA fragment was isolated containing 5' upstream sequences a nd part of the open reading frame corresponding to the lipoxygenase 1 cDNA (LoxA) expressed in barley grains during development and germinat ion. Lox1 transcription was shown to be methyl jasmonate (MeJA)- and w ound-inducible in leaves, but Lox1 transcripts were not detected in mi ldew-infected leaves, although this is a commonly observed response to pathogenic attack in various plants. Transient gene expression assays were used to identify a promoter region involved in MeJA-responsive e xpression. Analysis of 5' and 3' promoter deletions indicated that seq uences between -363 and -294 conferred MeJA-responsive expression. Del etions/replacements covering this part of the promoter further defined a MeJA-responsive region between -331 and -291. Insertion of the regi on -328 to -293 into the constitutive CaMV 35S promoter conferred MeJA -responsive expression. The 36 bp fragment contains the motif TGACG as inverted repeats, which has been previously identified as a binding s ite for bZIP transactivating factors. Site-directed mutagenesis on the se TGACG motifs abolished MeJA-responsive expression, clearly identify ing them as MeJA-responsive elements. Sequence comparisons found no si milar motif in other characterized promoters of MeJA-inducible genes, but suggested a common spatial structure which may serve as a binding site for transacting factors involved in the MeJA signal transduction pathway.