title: The OzT8 locus in rice protects leaf carbon assimilation rate and photosynthetic capacity under ozone stress.
abstract: Tropospheric ozone (O₃) is a phytotoxic air pollutant whose current background concentrations in parts of East Asia have caused estimated rice yield losses of up to 20%; currently, however, little is known about the mechanisms of O₃ tolerance in rice. We previously identified a quantitative trait locus (QTL) in rice called OzT8, which was associated with relative dry weight under ozone stress. The photosynthetic response in SL46, a Nipponbare (NB)-Kasalath chromosome segment substitution line (SL) containing the OzT8 locus, was compared to the parent NB in multiple ozone fumigation experiments (100 ppb, 8 h d⁻¹, 23 d). By day 23, SL46 showed significantly less reduction of photosynthetic capacity compared to NB; the maximum carboxylation rate of ribulose 1·5-bisphosphate carboxylase/oxygenase (Rubisco) decreased by 24% in SL46 compared to 49% in NB, and the maximum electron transport rate decreased by 16 and 39%, respectively. The midday carbon assimilation rates also showed a similar trend, but there was no genotypic difference in stomatal conductance. These results indicate that the OzT8 locus confers ozone tolerance via biochemical acclimation, not avoidance, making it a potentially valuable target for breeding of ozone tolerance into future rice lines. The sequence of photosynthetic response of rice to ozone stress and related tolerance factors are also discussed.
authors.affiliation: Division of Crop Production and Environment, Japan International Research Center for Agricultural Studies, Tsukuba, Ibaraki, Japan.
authors.forename: Charles P
authors.initials: CP
authors.lastname: Chen
authors.forename: Michael
authors.initials: M
authors.lastname: Frei
authors.forename: Matthias
authors.initials: M
authors.lastname: Wissuwa
mesh_terms: D000064:Acclimatization; D018533:Biomass; D002244:Carbon / Q000378:metabolism*; D002245:Carbon Dioxide / Q000378:metabolism; D002734:Chlorophyll / Q000032:analysis; D004579:Electron Transport; D017343:Genes, Plant; D005838:Genotype; D012275:Oryza / Q000235:genetics* / Q000502:physiology; D010126:Ozone / Q000378:metabolism*; D010788:Photosynthesis; D018515:Plant Leaves / Q000378:metabolism*; D054046:Plant Stomata / Q000502:physiology; D040641:Quantitative Trait Loci; D012273:Ribulose-Bisphosphate Carboxylase / Q000378:metabolism; D013312:Stress, Physiological
chemical_list: D002734:Chlorophyll; D002245:Carbon Dioxide; D010126:Ozone; D002244:Carbon; D012273:Ribulose-Bisphosphate Carboxylase