DEVELOPMENTAL AND HORMONAL-REGULATION OF THE ARABIDOPSIS CER2 GENE THAT CODES FOR A NUCLEAR-LOCALIZED PROTEIN REQUIRED FOR THE NORMAL ACCUMULATION OF CUTICULAR WAXES

The previously cloned CER2 gene is required for the normal accumulatio n of cuticular waxes and encodes a novel protein. Earlier reports sugg ested that the CER2 protein is either a membrane-bound component of th e fatty acid elongase complex or a regulatory protein. Cell fractionat ion and immunoblot analyses using polyclonal antibodies raised against a chemically synthesized peptide with a sequence based on the predict ed CER2 protein sequence have demonstrated that the 47-kD CER2 protein is soluble and nuclear localized. These results are consistent with C ER2 being a regulatory protein. Detailed studies of plants harboring a CER2 promoter/GUS transgene (CER2-GUS), in combination with immunoblo t analyses, revealed that CER2 is expressed and the CER2 protein accum ulates in a variety of organs and cell types. Expression is highest ea rly in the development of these organs and is epidermis specific in mo st tissues. In agreement with the activity of the CER2 promoter in hyp ocotyls, cuticular wax accumulates on this organ in a CER2-dependent f ashion. In leaves CER2 expression is confined to the guard cells, tric homes, and petioles. However, application of the cytokinin 6-benzylami nopurine induces ectopic expression of CER2-GUS in all cell types of l eaves that emerge following treatment.