A poplar DHDPS cDNA clone has been isolated by functional rescue of the dapA-deficient AT997 mutant of Escherichia coli. By sequence comparison between the poplar and maize DHDPS cDNAs, two oligonucleotides were designed to perform polymerase chain reaction (PCR) on Arabidopsis thaliana genomic DNA. The PCR fragment was subsequently used to isolate an Arabidopsis DHDPS genomic and cDNA clone.