Both pET28a(+)-AtGUS and pET28a(+)-AtGUS(-3t) were constructed and transformed into the E. coli BL21 strain, and the recombinant proteins AtGUS-E and AtGUS(-3t)-E were successfully expressed ( Figure 4) . The induction condition for the optimum production of the two recombinant proteins was 20uC with 0.4 mM IPTG. Both AtGUS-E and AtGUS(-3t)-E were purified through Ni-NTA sepharose (Figure 4) . The target protein was eluted with 150 mM imidazole. Furthermore, the concentrations of the soluble purified proteins of AtGUS-E and AtGUS(-3t)-E were determined as ,7 and ,12 mg/L, respectively. Both purified enzymes could hydrolyze GL into GAMG and GA.