PR1 is a pathogenesis‐related protein encoded in the parsley genome by a family of three genes (PR1–1, PR1–2 and PR1–3). Loss‐ and gain‐of‐function experiments in a transient expression system demonstrated the presence of two fungal elicitor responsive elements in each of the PR1–1 and PR1–2 promoters. These elements, W1, W2 and W3, contain the sequence (T)TGAC(C) and mutations that disrupt this sequence abolish function. Gel shift experiments demonstrated that W1, W2 and W3 are bound specifically by similar nuclear proteins. Three cDNA clones encoding sequence‐specific DNA‐binding proteins were isolated by South‐Western screening and these proteins, designated WRKY1, 2 and 3, also bind specifically to W1, W2 and W3. WRKY1, 2 and 3 are members of the family of sequence‐specific DNA‐binding proteins, which we call the WRKY family. Treatment of parsley cells with the specific oligopeptide elicitor Pep25 induced a transient and extremely rapid increase in mRNA levels of WRKY1 and 3. WRKY2 mRNA levels in contrast showed a concomitant transient decrease. These rapid changes in WRKY mRNA levels in response to a defined signal molecule suggest that WRKY1, 2 and 3 play a key role in a signal transduction pathway that leads from elicitor perception to PR1 gene activation.

We expressed a cDNA encoding the Arabidopsis thaliana defense-related protein ELI3-2 in Escherichia coli to determine its biochemical function. . Studies on the substrate specificity now revealed that ELI3-2 is an aromatic alcohol: NADP ؉ oxidoreductase (benzyl alcohol dehydrogenase). The enzyme showed a strong preference for various aromatic aldehydes as opposed to the corresponding alcohols. Highest substrate affinities were observed for 2-methoxybenzaldehyde, 3-methoxybenzaldehyde, salicylaldehyde, and benzaldehyde, in this order, whereas mannitol dehydrogenase activity could not be detected. These and previous results support the notion that ELI3-2 has an important role in resistance-related aromatic acid-derived metabolism.

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