Augmentation of CPD photolyase activity in japonica and indica rice increases their UVB resistance but still leaves the difference in their sensitivities

Abstract

Rice cultivars vary widely in their sensitivity to ultraviolet B (UVB, 280-320 nm). Specifically, many indica rice cultivars from tropical regions, where UVB radiation is higher, are hypersensitive to UVB. Photoreactivation mediated by the photolyase enzyme is the major pathway for repairing UVB-induced cyclobutane pyrimidine dimers (CPDs) in plants. Still, these UVB-sensitive cultivars are less able to repair CPDs through photoreactivation than UVB-resistant cultivars. Here, we produced CPD photolyase-overexpressing transgenic rice plants with higher CPD photolyase activity using UVB-sensitive rice Norin 1 (japonica) and UVB-hypersensitive rice Surjamkhi (indica) as parental line (PL) plants. The results show that these transgenic rice plants were much more resistant to UVB-induced growth inhibition than were PL cultivars. The present findings strongly indicate that UVB-resistance, caused by an increase in CPD photolyase activity, can be achieved in various rice cultivars. However, there was a difference in the level of reduction of UVB-induced growth inhibition among rice cultivars; the level of reduction of growth inhibition in transgenic rice plants generated from the indica strain was lower than that of transgenic rice plants generated from japonica strains. These results indicate that the growth of the UVB-hypersensitive indica strain was strongly inhibited by other factors in addition to CPD levels.

Light signaling and UV‐B‐mediated plant growth regulation

“…They absorb blue light and catalyze the conversion of dimer to monomer pyrimidines and thus reverting back to normal DNA (Britt 2004). Cyclobutane pyrimidine dimer photolyase is found to be necessary for UV-B resistance in rice and enhancing its expression helps rice plants to withstand UV-B-mediated growth inhibition (Hidema et al 2007;Teranishi et al 2012). Plants are also capable of carrying out excision repair in dark conditions, although to a lesser extent as compared to CPD removal in the presence of light (Liu et al 2000).…”

DNA Damage and Repair in Plants under Ultraviolet and Ionizing Radiations

“…A number of cofactors including the quality, timing, and quantity of photoreactivating light and damage levels largely modulate this repair [ 60 , 65 , 67 ]. Different genotypes exhibiting sensitivity to UV-B were reported to exhibit differential ability to repair UV-B-mediated DNA damage types (such as CPDs), where UV-B = sensitive cultivars were less able to repair CPDs through photoreactivation than UV-B resistant cultivars [ 68 ].…”

“…To date, photoreactivation and photolyases have been extensively reported in several plant species [ 65 – 77 ]. However, credible work has been performed on Oryza sativa cultivars, where photolyase has been evidenced as a major factor modulating O. sativa cultivar capability to repair DNA damage types [ 68 , 76 – 79 ]. Earlier also, the sensitivity of O. sativa to UV-B radiation was reported to vary among cultivars [ 78 ].…”

“…Earlier also, the sensitivity of O. sativa to UV-B radiation was reported to vary among cultivars [ 78 ]. Based on the exhibition of O. sativa cultivars potential for the level of CPD photolyase activity, O. sativa cultivars were clearly classified into three groups, which in turn depended on amino acid residues at positions 126 (UV-B resistant O. sativa , glutamine; UV-B sensitive and UV-B hypersensitive O. sativa , arginine) and 296 (UV-B resistant and UV-B sensitive O. sativa , glutamine; UV-B hypersensitive, histidine) [ 68 ]. It was also postulated that increasing the activity of the photolyase enzyme in O. sativa may increase their resistance to UV-B radiation [ 68 , 77 , 79 ].…”

“…Based on the exhibition of O. sativa cultivars potential for the level of CPD photolyase activity, O. sativa cultivars were clearly classified into three groups, which in turn depended on amino acid residues at positions 126 (UV-B resistant O. sativa , glutamine; UV-B sensitive and UV-B hypersensitive O. sativa , arginine) and 296 (UV-B resistant and UV-B sensitive O. sativa , glutamine; UV-B hypersensitive, histidine) [ 68 ]. It was also postulated that increasing the activity of the photolyase enzyme in O. sativa may increase their resistance to UV-B radiation [ 68 , 77 , 79 ]. In some recent reports, UV-B sensitive O. sativa cultivars were evidenced to exhibit less capability to repair CPDs through photoreactivation than UV-B resistant cultivars, where the authors considered an alteration of CPD photolyase activity resulting from spontaneously occurring mutations in the CPD photolyase gene [ 68 , 76 , 77 , 79 ].…”