Effect of LED Light Radiation on Antioxidant Activity and Agrobacterium-mediate Transformation of Azuki Bean Epicotyls

Influence of LED (light-emitting diode) light on antioxidant activity of etiolated azuki bean seedlings was studied. Free radical scavenging activity was measured with the standard DPPH (1, 1-diphenyl-2-picryl hydrazyl) method. Red (625-630 nm) light radiated seedlings expressed significantly higher scavenging activity than other treatments, such as blue (465-470 nm) and white light. In order to testing the possible influence of LED radiation to azuki bean epicotyls on Agrobacterium-mediated gene transfer efficiency, LED light (red, blue, or white) was applied simultaneously to plant segments with Agrobacterium tumefaciens strain EHA105 in which contains the binary plasmid pCAMBIA1201. Evidences of Agrobacterium- induced necrosis in target plant tissues and its link to reactive oxygen species (ROS) were investigated. The degrees of hypersensitive necrotic reaction in plant cells were affected by LED treatments. Irradiation with blue light resulted in increasing GUS gene expression in azuki bean explants and the increase in gene expression is possibly correlated with moderates DPPH-radical scavenging activity and low H2O2 accumulation in blue light-treated plant segments. Our data revealed that blue or red LED light treatment promotes Agrobacterium infection and blue light treatment improves transformation efficiency with higher cell viability. A possible application of our findings to the Agrobacterium-mediated azuki bean transformation was presented in the discussion.