Over-expression of the CHS gene enhances resistance of Arabidopsis leaves to high light

Previous studies have suggested that high light (HL) stress causes photoinhibition in plants, while anthocyanins could protect the photosynthetic apparatus against photoinhibition. However, the photoprotection mechanism of anthocyanins is still ambiguous. We studied physiological responses and molecular changes for CHS-overexpression lines (CHS1, CHS2, CHS3), Arabidopsis thaliana ecotype Columbia (Col), and T-DNA insertion lines of CHS (tt4) under HL (200 μmol m⁻² s⁻¹) to explore the photoprotection mechanism of anthocyanins. The results showed that HL induced anthocyanin synthesis and accumulation. The leaves of CHS-overexpression lines turned reddest and the genes, including CHS, DFR, ANS, were expressed at highest levels. Thus, the CHS-overexpression lines maintained the highest photosynthetic capacity and suffered the least damage from HL of the three phenotypes. However, the CHS enzyme and anthocyanins were undetectable in tt4 during the experiment. Correspondingly, chlorophyll fluorescence parameters of tt4 declined greatly. The photosynthetic apparatus and cell membranes were also impaired dramatically. The physiological characteristics of Col were compared between CHS-overexpression lines and tt4. Together, the results suggest that over-expression of CHS gene enhances HL resistance by synthesizing more anthocyanins, that anthocyanins enhance the adaptability of plants to HL and that they maintain photosynthetic capacity via both antioxidation and attenuation of light.