Characterization and differential expression analysis of artichoke phenylalanine ammonia-lyase coding sequences

Sequences encoding phenylalanine ammonia-lyase were isolated from artichoke, by using a sequence homology strategy, by screening a genomic library, and by 32RACE technology. These analyses and Southern blots suggested that, in artichoke, PAL is encoded by a small gene family. The sequences isolated from genomic DNA possess two exons and one intron at the conserved position as in most plant pal characterized to date. The 32RACE analysis also indicated that each member of the artichoke pal gene family was present as a pool of transcripts, different in the length of 32UTR. The deduced amino acid sequences were highly similar to those of PAL from lettuce and sunflower. One of the artichoke pal genes was completely sequenced and its 52 upstream region contained TATA, CAAT box and cis regulatory elements identified in other phenylpropanoid pathway genes as playing a role in UV and elicitor induction. The expression of three of the identified artichoke pal sequences was evaluated in different plant parts, developmental stages, and after wounding using gene-specific primers/probe combinations in real time PCR assays. The three putative genes were differentially expressed in the plant parts analysed and were developmentally regulated. Moreover, after leaf mechanical injury all of them were differentially regulated. The possible involvement of the single pal genes in different physiological processes is discussed.