Transcription of two members of a gene family encoding phenylalanine ammonia-lyase leads to remarkably different cell specificities and induction patterns.

Phenylalanine ammonia-lyase (PAL) catalyses the first committed step in the biosynthesis of phenylpropanoids, which perform a variety of functions in plant development and in their interactions with the environment. French bean contains a small family of genes encoding PAL and two of these genes, PAL2 and PAL3, have been shown to be differentially expressed at the mRNA level in bean tissues. The transcriptional activities of the PAL2 and PAL3 genes have been investigated by fusing their promoters to the reporter gene beta-glucuronidase (GUS) and transforming these constructs into Arabidopsis, potato and tobacco. The PAL2- and PAL3-GUS constructs exhibited different spatial and temporal patterns of expression during development and in response to environmental stimuli. The consistency of these data with previous mRNA analysis in bean suggests that the differential expression of these two PAL genes is, at least in part, a function of their promoter activities. New patterns of PAL2 and PAL3 promoter activities were also characterized. Some species-specific differences in GUS expression were observed and these may reflect differences in phenylpropanoid metabolism or the signals that modulate PAL gene transcription.