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 (P AL) form a small gene family similar to that found in many other plant genomes, A partial cDNA clone (cDNA1) was isolated from a cDNA librar y constructed with mRNA from the young stem tissue of P. kitakamiensis . A genomic clone, designated pal gl and corresponding to cDNA1, was i solated from the genomic library and characterized. pal gl consists of two exons separated by one intron and encodes a polypeptide of 714 am ino 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-speci fic 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.