Molecular cloning and characterization of the CER2 gene of Arabidopsis thaliana

Plants with defects in the synthesis of their epicuticular wax layer, eceriferum mutants (cer), are readily detected by the naked eye as bright green glossy plants when compared with the more glaucous normal plants. In a previous report, evidence was presented for the isolation of three lines from the Arabidopsis thaliana transformant collection (BRL5, BRL7 and BRL9) which failed to complement the cer2 mutant isolated previously. The analysis of the chemical composition of the epicuticular wax of these mutants suggests that the cer2 mutant of Arabidopsis is defective in very long chain fatty acid elongation. This paper reports the molecular cloning of the CER2 gene of Arabidopsis through the isolation of plant DNA flanking the site of T-DNA insertion as well as the characterization of the two independent T-DNA insertion mutant alleles, BRL5 and BRL9, of this gene. In the mutant line BRL5, T-DNA was found to be inserted in the second exon of the CER2 gene whereas in BRL9, T-DNA is inserted in the only intron of this gene. Nucleotide sequence analysis suggests that the ORF encodes a 47.3 kDa polypeptide. High levels of CER2 transcripts were detected in stems and flowers. The predicted amino acid sequence of the CER2 gene product reveals little homology with known protein sequences. In accordance with structural characterization of the T-DNA insertion mutants, no evidence of transcripts derived from the CER2 gene was found in either BRL5 or BRL9.