Cloning, Characterization and Functional Analysis of a Phenylalanine Ammonia-lyase Gene (FtPAL) from Fagopyrum tataricum Gaertn

Fagopyrum tataricum Garetn is a medicinal and nutrient-rich plant due to its high level of flavonoid content. Phenylalanine ammonia-lyase (PAL) is the first key enzyme in the phenylpropanoid biosynthesis pathway leading to the synthesis of flavonoids and other important secondary metabolites in plants. A PAL gene (designated as FtPAL) was cloned and characterized from tartary buckwheat. Southern hybridization analysis suggested that FtPAL belonged to a multigene family. Semiquantitative reverse transcription-PCR (RT-PCR) analysis showed that during the florescence period, FtPAL was most highly expressed in the stem, expressed at a moderate level in immature seeds and expressed to a lesser extent in roots and flower margins. Only weak expression was detected in leaves and mature seeds. The expression of the recombinant FtPAL protein in Escherichia coli BL21(DE3) was about 77 kDa, and it reached maximum yield after 5 h of induction. The enzymatic activity of recombinant FtPAL protein was analyzed, and results showed that it was specific to L-Phe, with an activity up to 35.7 IU/g. Our data suggest that FtPAL expression is tissue-specific, and it is a functional gene in F. tataricum.