Differential Accumulation of Antioxidant mRNAs in Arabidopsis thaliana Exposed to Ozone

Abstract

Antioxidant isoenzymes function to eliminate free radicals and are localized to severa1 different subcellular compartments within the plant cell. In Arabidopsis thaliana exposed to ozone (O3), we have monitored the accumulation of mRNAs encoding both cytosolic and chloroplastic antioxidant isoenzymes. Two different O, exposure protocols yielded similar results. Upon O, exposure, the steady-state levels of three mRNAs encoding cytosolic antioxidant isoenzymes (ascorbate peroxidase, copper/zinc superoxide dismutase, and glutathione S-transferase) increase. The glutathione Stransferase mRNA responds very quickly to the oxidative stress (2-fold increase in 30 min) and is elevated to very high levels, especially in plants grown with a 16-h photoperiod. In contrast, O, exposure causes a decline in the levels of two chloroplastic antioxidant mRNAs (iron superoxide dismutase and glutathione reductase) and two photosynthetic protein mRNAs (chlorophyll a/b-binding protein and ribulose-l,5-bisphosphate carboxylase/oxygenase small subunit). We show that this decline does not include all mRNAs encoding chloroplast-targeted proteins, since O, causes an elevation of mRNA encoding the chloroplast-localized tryptophan biosynthetic enzyme phosphoribosylanthranilate transferase. Two alternative hypotheses that could explain this differential mRNA accumulation in response to O, are discussed.

Enhanced ozone‐tolerance in wheat grown at an elevated CO2 concentration: ozone exclusion and detoxification

“…Our data do not indicate a significant roJe for enhanced antioxidant status, though we cannot rule out more subtle effects relating to the compartmentation of antioxidant systems, or to changed isoenzyme patterns (Foyer et al, 1994;Conklin & Last, 1995;Broadbent et al, 1995). There is, however, a clear indication that stomatal exclusion plays an important role (Fig.…”

Superoxide Dismutase in Arabidopsis: An Eclectic Enzyme Family with Disparate Regulation and Protein Localization

“…Tissue was collected during the fumigation and recovery periods, and the levels of CSD1, CSD2, CSD3, FSD1, FSD2, and MSD1 mRNAs were assayed by RNA-blot hybridization, with the results shown in Figure 10A. As previously described (Sharma and Davis, 1994;Conklin and Last, 1995), CSD1 mRNA accumulation was induced by ozone fumigation and continued to increase during the beginning of the recovery period (Fig. 10A).…”

“…Plants were fumigated 14 d postimbibition with 330 ppb ozone for 8 h. Unfumigated controls were grown with the fumigated plants except during fumigation, when they were kept in an equivalent chamber (Conklin and Last, 1995). Plants were allowed to recover overnight in charcoal-filtered (ozone-free) air.…”

“…All RNA isolation and blot hybridizations were as described by Conklin and Last (1995). Five micrograms of RNA was used on blots probed with CAB3, CSD1, CSD2, FSD1, and MSD.…”

The physiological, transcriptional and genetic responses of an ozone- sensitive and an ozone tolerant poplar and selected extremes of their F 2 progeny

“…Symptoms range from accelerated senescence (Karnosky et al, 1996) and a decrease in growth rate (Karnosky et al, 1996Wittig et al, 2009), to foliar injury manifested as necrotic lesions analogous to those formed during the hypersensitive response (HR) . Concomitant with these symptoms is an up-regulation of defence and stress related genes and compounds (Conklin and Last, 1995;Lindroth, 2010;Ludwikow et al, 2004), and a down-regulation of photosynthetic components (Conklin and Last, 1995;Glick et al, 1995). Although transcriptional responses to ozone and underlying QTL have been studied in annual model and non-model species (Frei et al, 2008;Li et al, 2006;Overmyer et al, 2008;Puckette et al, 2008), there is currently limited knowledge in perennials, such as trees, which form the keystone species of many terrestrial ecosystems.…”