Differential Wound Activation of Members of the Phenylalanine Ammonia-Lyase and 4-Coumarate: CoA Ligase Gene Families in Various Organs of Parsley Plants

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Abstract
We analyzed the developmental regulation and the activation by wounding of several stressrelated genes in various parsley organs. The genes encode phenylalanine ammonia-lyase (PAL) and 4-coumarate: CoA ligase (4 CL), two enzymes of general phenylpropanoid metabolism; a flavonoid specific enzyme, chalcone synthase (CHS); a furanocoumarin specific enzyme, bergaptol O-methyltransferase (BMT); and a pathogenesis-related protein (PR 1). All genes or gene families exhibited high levels of expression in roots and during certain stages of leaf development. PAL, 4 CL and CHS were preferentially expressed in young leaves, BMT and PR 1 in old leaves. An appreciable increase in CHS mRNA levels was observed in wounded leaves. By contrast, root wounding led to a decrease in the existing CHS m RNA levels. A biphasic response (a decrease followed by an increase) to wounding was seen for BMT and PR 1 m RNA s in roots and for BMT mRNA in attached leaves. Using gene-specific oligonucleotide probes to measure the expression rates of three of the four PAL genes and of the two 4 CL genes separately we observed a differential behavior of the individual family members under many of the conditions tested. While PAL-3 was preferentially activated in wounded leaves and 4CL-1 in wounded roots, PAL-2 and 4C L-2 were primarily responsible for the high constitutive expression levels in roots and flowering stems respectively. Despite the differential expression of their individual members, the PAL and 4 CL gene families displayed very similar changes in the overall patterns of expression, reflecting their closely related functions in phenylpropanoid metabolism.

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