IMMUNOLOCALIZATION OF CINNAMYL ALCOHOL-DEHYDROGENASE-2 (CAD-2) INDICATES A GOOD CORRELATION WITH CELL-SPECIFIC ACTIVITY OF CAD-2 PROMOTER IN TRANSGENIC POPLAR SHOOTS

Cinnamyl alcohol dehydrogenase 2 (CAD 2) localization and the cell-spe cific activity of the eucalyptus CAD 2 promoter were investigated by C AD 2 immunogold localization and promoter beta-glucuronidase (GUS) his tochemistry in apical and mature parts of stable transformed poplar (P opulus tremula x P. alba) stems. Both CAD 2 protein and GUS activity w ere found to be confined in the same types of cells in the shoot apice s, particularly in the determined meristematic cells in leaf axils and shell zones, procambium and developing tracheids. Within mature stems , CAD 2 and GUS were also identified in cambium and in fully or partia lly lignified cells derived from it (young xylem, developing phloem fi bres, chambered parenchyma cells around phloem). Additionally, GUS act ivity was found in the scale leaves of apical shoot buds and in the ro ots (namely in the procambium, cambium, phellogen, young xylem, pericy cle) of transformed plants. By employing immunogold cytochemistry, CAD 2 was shown to be localized in the cytoplasm within cambial, ray and young xylem cells in stems, the gold particles being randomly attached to endoplasmic reticulum and Golgi-derived vesicles. These results su pport a crucial role for CAD 2 in lignification and indicate a new rol e for this enzyme in branching events within the shoot apex and during lateral root formation.