TRANSCRIPTION OF 2 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 i n the biosynthesis of phenylpropanoids, which perform a variety of fun ctions in plant development and in their interactions with the environ ment. French bean contains a small family of genes encoding PAL and tw o of these genes, PAL2 and PAL3, have been shown to be differentially expressed at the mRNA level in bean tissues. The transcriptional activ ities of the PAL2 and PAL3 genes have been investigated by fusing thei r promoters to the reporter gene beta-glucuronidase (GUS) and transfor ming these constructs into Arabidopsis, potato and tobacco. The PAL2- and PAL3-GUS constructs exhibited different spatial and temporal patte rns 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 pat terns of PAL2 and PAL3 promoter activities were also characterized. So me species-specific differences in GUS expression were observed and th ese may reflect differences in phenylpropanoid metabolism or the signa ls that modulate PAL gene transcription.