title: A methyl viologen-resistant mutant of Arabidopsis, which is allelic to ozone-sensitive rcd1, is tolerant to supplemental ultraviolet-B irradiation.
abstract: To better understand the role of active oxygen species (AOS) in acquired resistance to increased levels of ultraviolet (UV)-B irradiation in plants, we isolated an Arabidopsis mutant that is resistant to methyl viologen, and its sensitivity to UV-B was investigated. A complementation test revealed that the obtained mutant was allelic to the ozone-sensitive radical-induced cell death1-1 (rcd1-1). Therefore, this mutant was named rcd1-2. rcd1-2 was recessive and nearly 4-fold more resistant to methyl viologen than wild type. It exhibited a higher tolerance to short-term UV-B supplementation treatments than the wild type: UV-B-induced formation of cyclobutane pyrimidine dimers was reduced by one-half after 24 h of exposure; the decrease in quantum yield of photosystem II was also diminished by 40% after 12 h of treatment. Furthermore, rcd1-2 was tolerant to freezing. Steady-state mRNA levels of plastidic Cu/Zn superoxide dismutase and stromal ascorbate peroxidase were higher in rcd1-2 than in wild type, and the mRNA level of the latter enzyme was enhanced by UV-B exposure more effectively in rcd1-2. UV-B-absorbing compounds were more accumulated in rcd1-2 than in wild type after UV-B exposure for 24 h. These findings suggest that rcd1-2 methyl viologen resistance is due to the enhanced activities of the AOS-scavenging enzymes in chloroplasts and that the acquired tolerance to the short-term UV-B exposure results from a higher accumulation of sunscreen pigments. rcd1 appears to be a mutant that constitutively shows stress responses, leading to accumulation of more pigments and AOS-scavenging enzymes without any stresses.
authors.affiliation: Division of Biological Sciences, Graduate School of Environmental Earth Science, Hokkaido University, Sapporo, 060-0810 Japan.
authors.forename: Takahiro
authors.initials: T
authors.lastname: Fujibe
authors.forename: Hikaru
authors.initials: H
authors.lastname: Saji
authors.forename: Keita
authors.initials: K
authors.lastname: Arakawa
authors.forename: Naoto
authors.initials: N
authors.lastname: Yabe
authors.forename: Yuichi
authors.initials: Y
authors.lastname: Takeuchi
authors.forename: Kotaro T
authors.initials: KT
authors.lastname: Yamamoto
mesh_terms: D000483:Alleles; D017360:Arabidopsis / Q000187:drug effects / Q000235:genetics* / Q000378:metabolism / Q000528:radiation effects; D001483:Base Sequence; D004249:DNA Damage; D018744:DNA, Plant / Q000235:genetics / Q000528:radiation effects; D004351:Drug Resistance / Q000235:genetics; D016166:Free Radical Scavengers / Q000378:metabolism; D005615:Freezing; D015870:Gene Expression; D017343:Genes, Plant; D018869:Heat-Shock Response; D006861:Hydrogen Peroxide / Q000378:metabolism; D009154:Mutation; D010126:Ozone / Q000494:pharmacology; D010269:Paraquat / Q000494:pharmacology; D010788:Photosynthesis / Q000528:radiation effects; D012333:RNA, Messenger / Q000235:genetics / Q000378:metabolism; D018749:RNA, Plant / Q000235:genetics / Q000378:metabolism; D011836:Radiation Tolerance / Q000235:genetics; D014466:Ultraviolet Rays
chemical_list: D018744:DNA, Plant; D016166:Free Radical Scavengers; D012333:RNA, Messenger; D018749:RNA, Plant; D010126:Ozone; D006861:Hydrogen Peroxide; D010269:Paraquat