THE APPLICATION OF EXOGENOUS GIBBERELLIC ACID ENHANCES WHEAT SEEDLINGS UV-B TOLERANCE BY AMELIORATING DNA DAMAGE AND MANIPULATING UV-ABSORBING COMPOUND BIOSYNTHESIS IN WHEAT SEEDLING LEAVES

DNA damage is one of the key parameters to detect UV-B tolerance because DNA is one of the primary targets for UV-B light. Here, we evaluated UV-B stress-induced genomic DNA damages and its self-repair ability in wheat seedlings with or without gibberellic acid (GA(3)) treatment. The application of exogenous GA(3) exhibited the better phenotypic development, less inhibition effects in biomass production and a lower accumulation level of cyclobutane pyrimidine dimer (CPD) and (6-4) photoproducts (6-4PPs) in leaves of wheat seedlings under supplementary UV-B stress than those without GA(3) treatment, indicating that GA(3) ameliorated the detrimental effects and DNA damages induced by the enhanced UV-B stress, in which the 150mg L-1 of GA(3) is the most effective treatment. After exogenous GA(3) treatment, the UV-absorbing compounds (UACs) contents and DNA photolyase activity also significantly increased, whereas reactive oxygen species (ROS) production were similar between two groups with or without GA(3) application under UV-B stress. These results have demonstrated that GA(3) enhanced wheat seedlings UV-B tolerance by initiating DNA damage repair pathway in leaves of wheat seedlings exposed to supplementary UV-B stress, which were mainly implemented through activating DNA photorepair capability and elevating UV-B absorbance amounts in vivo in plants.