Fresh onion bulbs were cut into 0.25-cm
2
pieces and pre-cultured in MSB
medium in
the dark for 24 h; the onion pieces were then immersed in a solution containing Agrobacterium
EHA105 and a plasmid (pCAMBIA1301-xylA-Chi-P to pCAMBIA1301-xylA-Chi-P
for 15 min, then
cultured in the dark for 3 days. Transformed onion epidermal cells and control cells were treated
with 5.0 mM SA or distilled water for 84 h and then stained for GUS activity by incubating overnight
5
)
5in X-gluc, 0.1 mM phosphate buffer, pH 7.0, 1 mM EDTA, 5 mM potassium ferrocyanide, Triton
X-100, and N,N-dimethylformamide at 37°C, followed by decolorizing in 70% ethanol. GUS enzyme
activity in transformed onion epidermal cells was detected as previously described (Ma et al. 2010).