Fig. 2.

The noninvasive detection of ¹O₂ during embryogenesis using the ¹O₂-specific AAA-LUC reporter gene. (A) ¹O₂-induced expression of LUC in plants. Transgenic flu plants grown under continuous light were either shifted to the dark for 8 h and reexposed to light (D/L) or kept under continuous light (LL). The image of the D/L-treated plant was taken after 1 h of reillumination. (B) Luciferase activity at different stages of embryogenesis of transgenic WT plants expressing AAA:LUC. Immature seeds were taken from siliques at 4, 7, 13, and 17 DAA and kept under dim light (LL) or transferred to the dark for 4 h (D). Luciferase activity was detectable in immature “green” seeds at 13 DAA, when they were exposed to dim light but not after they had been kept in the dark. Similar results were obtained with seeds still attached to opened siliques. (C) Luciferase activity at different stages of embryogenesis of transgenic flu plants expressing AAA:LUC. Seeds were taken from siliques at 4, 7, 13, and 17 DAA and kept under dim light (LL), transferred to the dark for 4 h (D), or reexposed to light after 4 h of dark treatment (D/L). In the dark, free Pchlide accumulated that during reillumination acted as a photosensitizer and generated ¹O₂ in immature flu seeds taken from siliques at 4, 7, and 13 DAA.