Ultraviolet-B-induced DNA damage and ultraviolet-B tolerance mechanisms in species with different functional groups coexisting in subalpine moorlands
High doses of ultraviolet-B (UV-B; 280–315 nm) radiation can have detrimental effects on plants, and especially damage their DNA. Plants have DNA repair and protection mechanisms to prevent UV-B damage. However, it remains unclear how DNA damage and tolerance mechanisms vary among field species. We studied DNA damage and tolerance mechanisms in 26 species with different functional groups coexisting in two moorlands at two elevations. We collected current-year leaves in July and August, and determined accumulation of cyclobutane pyrimidine dimer (CPD) as UV-B damage and photorepair activity (PRA) and concentrations of UV-absorbing compounds (UACs) and carotenoids (CARs) as UV-B tolerance mechanisms. DNA damage was greater in dicot than in monocot species, and higher in herbaceous than in woody species. Evergreen species accumulated more CPDs than deciduous species. PRA was higher in Poaceae than in species of other families. UACs were significantly higher in woody than in herbaceous species. The CPD level was not explained by the mechanisms across species, but was significantly related to PRA and UACs when we ignored species with low CPD, PRA and UACs, implying the presence of another effective tolerance mechanism. UACs were correlated negatively with PRA and positively with CARs. Our results revealed that UV-induced DNA damage significantly varies among native species, and this variation is related to functional groups. DNA repair, rather than UV-B protection, dominates in UV-B tolerance in the field. Our findings also suggest that UV-B tolerance mechanisms vary among species under evolutionary trade-off and synergism.
KeywordsPhotorepair Ultraviolet-B protection Trade-off Interspecific variation Cyclobutane pyrimidine dimer
We thank Drs Riichi Oguchi, Hiroshi Ozaki, Soichiro Nagano, and Michio Oguro for valuable comments. We are also grateful to Dr Mika Teranishi, Hiroko Yamaguchi, Nan Li, and Mami Kanbayashi for field and laboratory support. This study was supported by grants from MEXT, Japan (KAKENHI, nos. 21114009, 25291095, 25660113); the Global Environment Research Fund (F-092/D-0904) of the Ministry of the Environment, Japan; the Global COE Program the Center for Ecosystem Management Adapting to Global Change (J03) of MEXT, Japan; CREST, JST, Japan; and a research grant from the Mitsui Environment Fund.
Author contribution statement
KH and QWW conceived and designed the experiment. QWW, CK, and KH collected samples in the field. QWW and JH performed the biochemical analyses. QWW analyzed the data and wrote the manuscript. KH, CK, and JH provided comments.
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