Involvement of Reactive Oxygen Species and Mitochondrial Proteins in Biophoton Emission in Roots of Soybean Plants under Flooding Stress

To
understand the mechanism of biophoton emission, ROS and mitochondrial
proteins were analyzed in soybean plants under flooding stress. Enzyme
activity and biophoton emission were increased in the flooding stress
samples when assayed in reaction mixes specific for antioxidant enzymes
and reactive oxygen species; although the level of the hydroxyl radicals
was increased at day 4 (2 days of flooding) compared to nonflooding
at day 4, the emission of biophotons did not change. Mitochondria
were isolated and purified from the roots of soybean plants grown
under flooding stress by using a Percoll gradient, and proteins were
analyzed by a gel-free proteomic technique. Out of the 98 mitochondrial
proteins that significantly changed abundance under flooding stress,
47 increased and 51 decreased at day 4. The mitochondrial enzymes
fumarase, glutathione-S-transferase, and aldehyde dehydrogenase increased
at day 4 in protein abundance and enzyme activity. Enzyme activity
and biophoton emission decreased at day 4 by the assay of lipoxygenase
under stress. Aconitase, acyl CoA oxidase, succinate dehydrogenase,
and NADH ubiquinone dehydrogenase were up-regulated at the transcription
level. These results indicate that oxidation and peroxide scavenging
might lead to biophoton emission and oxidative damage in the roots
of soybean plants under flooding stress.