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Low antioxidant concentrations impact on multiple signalling pathways in Arabidopsis thaliana partly through NPR1.

Brosché M, Kangasjärvi J - J. Exp. Bot. (2012)

Bottom Line: In contrast, low glutathione concentrations in cad2 or pad2 reduced expression of SA-regulated genes.Furthermore, NPR1 was found to be a positive regulator of JA-induced expression of MDHAR3 and TAT3.The vtc1 and npr1 mutants were sensitive to glucose inhibition of seed germination; an opposite response was found in cad2 and pad2.

View Article: PubMed Central - PubMed

Affiliation: Department of Biosciences, University of Helsinki, Helsinki, Finland. mikael.brosche@helsinki.fi

ABSTRACT
Production of reactive oxygen species (ROS) is linked to signalling in both developmental and stress responses. The level of ROS is controlled by both production and removal through various scavengers including ascorbic acid and glutathione. Here, the role of low ascorbic acid or glutathione concentrations was investigated on ozone-induced cell death, defence signalling, and developmental responses. Low ascorbic acid concentrations in vtc1 activated expression of salicylic acid (SA)-regulated genes, a response found to be dependent on the redox-regulated transcriptional co-regulator NPR1. In contrast, low glutathione concentrations in cad2 or pad2 reduced expression of SA-regulated genes. Testing different responses to jasmonic acid (JA) revealed the presence of at least two separate JA signalling pathways. Treatment of the vtc1 mutant with JA led to hyper-induction of MONODEHYDROASCORBATE REDUCTASE3, indicating that low ascorbic acid concentrations prime the response to JA. Furthermore, NPR1 was found to be a positive regulator of JA-induced expression of MDHAR3 and TAT3. The vtc1 and npr1 mutants were sensitive to glucose inhibition of seed germination; an opposite response was found in cad2 and pad2. Overall, low ascorbic acid concentrations mostly led to opposite phenotypes to low glutathione concentrations, and both antioxidants interacted with SA and JA signalling pathways.

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Sugar inhibition of germination. The germination frequency of seeds from antioxidant mutants grown on MS media supplemented with 300 mM glucose (A) or 300 m M mannitol (B) for 7 d. Seeds were scored in three different categories: no germination, white seedlings, and green seedlings. Values are the mean ±SE of three biological repeats. n=150–300.
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fig8: Sugar inhibition of germination. The germination frequency of seeds from antioxidant mutants grown on MS media supplemented with 300 mM glucose (A) or 300 m M mannitol (B) for 7 d. Seeds were scored in three different categories: no germination, white seedlings, and green seedlings. Values are the mean ±SE of three biological repeats. n=150–300.

Mentions: High glucose concentrations reduce germination and growth of Arabidopsis seeds on MS medium. A complex network of signals is involved in this response, including general metabolism and the plant hormones abscisic acid and ethylene (Ramon et al., 2008). After 7 d of growth on 300 mM glucose, three different classes of seedlings were observed: seeds that did not germinate, white seedlings, and green seedlings (Fig. 8A). The growth of npr1, vtc1, and particularly npr1 vtc1 was inhibited by glucose. Interestingly, growth of npr1 cad2 and npr1 pad2 double mutants was not inhibited as in npr1, indicating that all three components ascorbic acid, glutathione, and NPR1 were involved in sugar signalling. No major changes were observed on growth in the osmotic stress control mannitol (Fig. 8B).


Low antioxidant concentrations impact on multiple signalling pathways in Arabidopsis thaliana partly through NPR1.

Brosché M, Kangasjärvi J - J. Exp. Bot. (2012)

Sugar inhibition of germination. The germination frequency of seeds from antioxidant mutants grown on MS media supplemented with 300 mM glucose (A) or 300 m M mannitol (B) for 7 d. Seeds were scored in three different categories: no germination, white seedlings, and green seedlings. Values are the mean ±SE of three biological repeats. n=150–300.
© Copyright Policy - creative-commons
Related In: Results  -  Collection

License 1 - License 2
Show All Figures
getmorefigures.php?uid=PMC3295383&req=5

fig8: Sugar inhibition of germination. The germination frequency of seeds from antioxidant mutants grown on MS media supplemented with 300 mM glucose (A) or 300 m M mannitol (B) for 7 d. Seeds were scored in three different categories: no germination, white seedlings, and green seedlings. Values are the mean ±SE of three biological repeats. n=150–300.
Mentions: High glucose concentrations reduce germination and growth of Arabidopsis seeds on MS medium. A complex network of signals is involved in this response, including general metabolism and the plant hormones abscisic acid and ethylene (Ramon et al., 2008). After 7 d of growth on 300 mM glucose, three different classes of seedlings were observed: seeds that did not germinate, white seedlings, and green seedlings (Fig. 8A). The growth of npr1, vtc1, and particularly npr1 vtc1 was inhibited by glucose. Interestingly, growth of npr1 cad2 and npr1 pad2 double mutants was not inhibited as in npr1, indicating that all three components ascorbic acid, glutathione, and NPR1 were involved in sugar signalling. No major changes were observed on growth in the osmotic stress control mannitol (Fig. 8B).

Bottom Line: In contrast, low glutathione concentrations in cad2 or pad2 reduced expression of SA-regulated genes.Furthermore, NPR1 was found to be a positive regulator of JA-induced expression of MDHAR3 and TAT3.The vtc1 and npr1 mutants were sensitive to glucose inhibition of seed germination; an opposite response was found in cad2 and pad2.

View Article: PubMed Central - PubMed

Affiliation: Department of Biosciences, University of Helsinki, Helsinki, Finland. mikael.brosche@helsinki.fi

ABSTRACT
Production of reactive oxygen species (ROS) is linked to signalling in both developmental and stress responses. The level of ROS is controlled by both production and removal through various scavengers including ascorbic acid and glutathione. Here, the role of low ascorbic acid or glutathione concentrations was investigated on ozone-induced cell death, defence signalling, and developmental responses. Low ascorbic acid concentrations in vtc1 activated expression of salicylic acid (SA)-regulated genes, a response found to be dependent on the redox-regulated transcriptional co-regulator NPR1. In contrast, low glutathione concentrations in cad2 or pad2 reduced expression of SA-regulated genes. Testing different responses to jasmonic acid (JA) revealed the presence of at least two separate JA signalling pathways. Treatment of the vtc1 mutant with JA led to hyper-induction of MONODEHYDROASCORBATE REDUCTASE3, indicating that low ascorbic acid concentrations prime the response to JA. Furthermore, NPR1 was found to be a positive regulator of JA-induced expression of MDHAR3 and TAT3. The vtc1 and npr1 mutants were sensitive to glucose inhibition of seed germination; an opposite response was found in cad2 and pad2. Overall, low ascorbic acid concentrations mostly led to opposite phenotypes to low glutathione concentrations, and both antioxidants interacted with SA and JA signalling pathways.

Show MeSH