In order to study the enzymatic activity of Arabidopsis poly(ADP-ribose) polymerase 1(PARP1),the cDNA fragment of PARP1 was amplified using Reverse-Transcription PCR method from Arabidopsis seedlings treated by bleomycin.The cDNA sequence was cloned into prokaryotic expression vector pET32 and the resultant pET32a-PARP1 plasmid was transformed into Escherichia coli host strain Origami(DE3).IPTG was added into the culture to a final concentration of 0.3 mmol/L to induce expression at 16 ℃ for 20 h.The recombinant protein TRX-PARP1 was purified and then assayed for enzymatic activity with the substrate NAD⁺ and broken DNA in the reaction buffer.TRX-PARP1 protein band shifted upwardly in a time course on SDS-PAGE gel.Western blotting using anti-PARP1 antibody further confirmed that the molecular mass of TRX-PARP1 increased gradually,due to the linkage of ADP ribose molecules onto the protein.In contrast,the fusion tag protein Thioredoxin(TRX) did not show any change in mobility.These data demonstrated that Arabidopsis PARP1 produced in E.coli has auto-modification activity,which facilitates the functional study of PARP1 in Arabidopsis.