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. 2012 Apr;35(4):668-81.
doi: 10.1111/j.1365-3040.2011.02443.x. Epub 2011 Nov 15.

Minimal influence of G-protein null mutations on ozone-induced changes in gene expression, foliar injury, gas exchange and peroxidase activity in Arabidopsis thaliana L

Fitzgerald Booker  1 , Kent Burkey, Patrick Morgan, Edwin Fiscus, Alan Jones
Affiliations

Minimal influence of G-protein null mutations on ozone-induced changes in gene expression, foliar injury, gas exchange and peroxidase activity in Arabidopsis thaliana L

Fitzgerald Booker et al. Plant Cell Environ. 2012 Apr.

Abstract

Ozone (O(3)) uptake by plants leads to an increase in reactive oxygen species (ROS) in the intercellular space of leaves and induces signalling processes reported to involve the membrane-bound heterotrimeric G-protein complex. Therefore, potential G-protein-mediated response mechanisms to O(3) were compared between Arabidopsis thaliana L. lines with null mutations in the α- and β-subunits (gpa1-4, agb1-2 and gpa1-4/agb1-2) and Col-0 wild-type plants. Plants were treated with a range of O(3) concentrations (5, 125, 175 and 300 nL L(-1)) for 1 and 2 d in controlled environment chambers. Transcript levels of GPA1, AGB1 and RGS1 transiently increased in Col-0 exposed to 125 nL L(-1) O(3) compared with the 5 nL L(-1) control treatment. However, silencing of α and β G-protein genes resulted in little alteration of many processes associated with O(3) injury, including the induction of ROS-signalling genes, increased leaf tissue ion leakage, decreased net photosynthesis and stomatal conductance, and increased peroxidase activity, especially in the leaf apoplast. These results indicated that many responses to O(3) stress at physiological levels were not detectably influenced by α and β G-proteins.

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Figures

Figure 1
Figure 1
Relative ion leakage from leaves of Col-0, gpa1-4, agb1-2 and gpa1-4/agb1-2 plants following a 7 h exposure to 5, 125, 175 or 300 nL L−1 O3. Statistically significant pairwise comparisons with the respective control treatment (5 nL L−1) are indicated as: ***, P ≤ 0.001. Values are LSMEANS ± SE.
Figure 2
Figure 2
Net photosynthesis (An) (a) and stomatal conductance (gs) (b) of Col-0, gpa1-4, agb1-2 and gpa1-4/agb1-2 following treatment with 5, 125 or 175 nL L−1 O3 for 7 h d−1. Average results after 1 and 2 d of exposures are shown. Statistically significant pairwise comparisons with the respective control treatment (5 nL L−1) are indicated as: *, P ≤ 0.05; **, P ≤ 0.01; ***, P ≤ 0.001. Values are LSMEANS ± SE.
Figure 3
Figure 3
Ascorbate (a,b) and DAF (c,d) peroxidase activity in extracts of leaf tissues from Col-0, gpa1-4, agb1-2 and gpa1-4/agb1-2 plants treated for one (a,c) and two (b,d) 7 h periods with either 5 (control), 125 or 175 nL L−1 O3. Values are LSMEANS ± SE and the statistically significant pairwise comparisons with the respective 5 nL L−1 O3 control treatment are indicated as: *, P ≤ 0.05; **, P ≤ 0.001; ***, P ≤ 0.0001. APX, ascorbate peroxidase; DAF, 2,7-diaminofluorene.
Figure 4
Figure 4
Ascorbate (a,b) and DAF (c,d) peroxidase activity in IWF extracts from Col-0, gpa1-4, agb1-2 and gpa1-4/agb1-2 plants treated for one (a,c) and two (b,d) 7 h periods with either 5 (control), 125 or 175 nL L−1 O3. Values are LSMEANS ± SE and the statistically significant pairwise comparisons with the respective control (5 nL L−1 O3) are indicated as: *, P ≤ 0.05; **, P ≤ 0.01; ***, P ≤ 0.001. APX, ascorbate peroxidase; DAF, 2,7-diaminofluorene; IWF, intercellular washing fluid.
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References

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