The desired DNA product of dsr1 and dsr2 was amplified from the total DNA of the L0309 screened in this lab by PCR with two pairs of gene specific primers.The segment of dsr1 and dsr2 was inserted into pUC19 vector and integrated into the entire gene of dsrx.The result of restriction endonuclease mapping and sequencing shows that 4566 bp of dsrx covers the entire open reading frame,encoding 1522 amino acid residues.There is an identity of 99% between the gene of U81374 and dsrx about their nuclear acid sequences.The homology of the deduced amino acid level amount to 98.49% with that of U81374.