Immunological detection and cellular localization of the phenylalanine ammonia-lyase of a hybrid aspen

The cellular-localization pattern of promoter activities of two phenylalanine ammonia-lyase (PAL; EC 4.3.1.5) genes, palg1 and palg2b, of a hybrid aspen, Populus kitakamiensis, was determined using the GUS reporter system. The strong activities of palg2b promoter were detected in lignified tissues such as xylem and phloem fiber cells of the aspen stem, suggesting the specific function of the PALg2b in lignin biosynthesis. Immunoelectron microscopy and sub-cellular fractionation of xylem cells showed that the PAL activity was detected in both the plastid and cytosol of the xylem ray-parenchyma cells and the cytosol in the developing xylem cells of the aspen mature stem. Our results of the biochemical characterization of xylem PAL protein suggested that the PAL localization was varied during cell differentiation of the aspen xylem to function in lignin biosynthesis.