Regulation of the wound-induced myrosinase-associated protein transcript in Brassica napus plants.

Two slightly differing cDNA clones corresponding to the wound-inducible form of a previously characterized seed myrosinase-associated protein (MyAP) have been isolated from Brassica napus L. The transcripts corresponding to the induced MyAP (iMyAP) were found to be developmentally regulated in various vegetative organs. Both young and old leaves exhibited wound-inducible iMyAP expression. Furthermore, in the young plant, wounding resulted in a systemic increase in leaves located both acropetally and basipetally to the wounded leaf. Also, the iMyAP transcripts were induced by methyl jasmonate, jasmonic acid and abscisic acid. The different inductions could be antagonized by salicylic acid. A general responsiveness in methyl-jasmonate-treated leaves was demonstrated by in situ hybridization. No effect on the amount of iMyAP transcript was detected after feeding the plants with the ethylene precursor 1-aminocyclopropane-1-carboxylic acid. The similarity between MyAP and a lipase from Arabidopsis thaliana indicated a possible function in liberating acylated glucosinolates from their acyl group, thereby making them available for hydrolysis by the myrosinase enzymes. We also report on a reduction in the amount of myrosinase transcripts derived from the vegetatively expressed MB-gene family after treatment with exogenously applied salicylic acid or abscisic acid.