UVB-induced DNA damage and photoenzymatic repair in two-spotted spider mite, Tetranychus urticae

Abstract: Ambient solar ultraviolet-B radiation (UVB) has lethal effects for the two-spotted spider mite, Tetranychus urticae. Recent studies revealed the significance of photoreactivation for the survival of spider mites under ambient UVB radiation. However, physiological mechanisms of photoreactivation are poorly understood, and thus, not validated in spider mites. Generally, the most abundant DNA lesion induced by UVB is cyclobutane-pyrimidine dimer (CPD). Photoenzymatic repair (PER) is one of the main repair mechanisms to counteract this lesion. PER is the mechanism that UV-induced DNA lesions are directly normalized by photolyase enzyme reaction using absorbed light energy and considered to cause the photoreactivation phenomenon in general. We verified the UVB-induced CPD in the genomic DNA of spider mites and photolyase gene expression with substantial effects on their survival. The survival of larvae by 30 min UVB exposure was 0% while the survival of larvae kept under dark conditions was 100%. After UVB irradiation, survival rate was recovered by 30 min exposure to VIS light (98.6%) but not when kept under dark conditions (0%). About UV-induced DNA damage, CPD increased with cumulative UVB dose and decreased by VIS exposure than when kept under dark conditions, suggesting that CPD absolutely affects the survival and that photoreactivation is induced by the CPD repair activity of the photo-enzymatic repair. However, the expression level of CPD photolyase gene did not vary in each irradiation treatment. We consider the possibility of other expression mechanisms. In conclusion, we identified the UVB-induced DNA damage, photoreactivation repair, and CPD photolyase expression in T. urticae larvae. Our data highlight the possibility of applying UVB irradiation for the integrated pest management.Extended abstract