Molecular cloning, characterization and expression of phenylalanine ammonia-lyase gene from Ginkgo biloba

A full-length cDNA and genomic DNA of phenylalanine ammonia-lyase gene, which catalyzes the first step in the flavonoid biosynthetic pathway, were isolated from Ginkgo biloba for the first time (designated as GbPAL, GenBank Accession No. EU071050). The cDNA and genomic DNA sequences of GbPAL were the same, in other words, this gene is intronless. The coding region of the gene was 2172 bp long, and its deduced protein consists of 724 amino acids with a predicted molecular mass of 79.1 kDa and a pI of 5.96. The deduced GbPAL protein showed high identities to other plant PALs. Southern hybridization analysis of the genomic DNA indicated that GbPAL belonged to a small multi-gene family. Tissue expression analysis by real-time PCR revealed that GbPAL constitutively expressed in all the tested tissues, especially highly in leaf and stem. GbPAL was also observed to be induced by a variety of stresses including UV-B, wounding, cold and salicylic acid. Temporal expression profiling analyses showed that the transcription levels of GbPAL were significantly correlated with flavonoid accumulation, suggesting that GbPAL might play a regulatory role in flavonoid biosynthesis in leaves of G. biloba at the transcriptional level.