STRUCTURE AND TISSUE-SPECIFIC EXPRESSION OF GENES FOR PHENYLALANINE AMMONIA-LYASE FROM A HYBRID ASPEN, POPULUS-KITAKAMIENSIS

In Populus kitakamiensis, the genes for phenylalanine ammonia-lyase (PAL) form a small gene family similar to that found in many other plant genomes, A partial cDNA clone (cDNA1) was isolated from a cDNA library constructed with mRNA from the young stem tissue of P. kitakamiensis. A genomic clone, designated pal gl and corresponding to cDNA1, was isolated from the genomic library and characterized. pal gl consists of two exons separated by one intron and encodes a polypeptide of 714 amino acid residues. Another genomic clone, pal g2a, was also isolated, It has one intron and encodes a polypeptide of 682 amino acid residues, Transcripts of pal gl and pal g2a were detected by use of gene-specific probes, pal gl mRNA was expressed in a tissue-specific manner and was detected at the highest levels in young tissues near the shoot bud, By contrast, pal g2a mRNA was mainly accumulated in mature stems and appeared not to be expressed in young tissues.