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New ABA-hypersensitive Arabidopsis mutants are affected in loci mediating responses to water deficit and Dickeya dadantii infection.

Plessis A, Cournol R, Effroy D, Silva Pérez V, Botran L, Kraepiel Y, Frey A, Sotta B, Cornic G, Leung J, Giraudat J, Marion-Poll A, North HM - PLoS ONE (2011)

Bottom Line: The has2 mutant also exhibited increased germination inhibition by ABA, while ABA-inducible gene expression was not modified on dehydration, indicating the mutated gene affects early ABA-signalling responses that do not modify transcript levels.In contrast, weak ABA-hypersensitivity relative to mutant developmental phenotypes suggests that HAS3 regulates drought responses by both ABA-dependent and independent pathways. has1 mutant phenotypes were only apparent on stress or ABA treatments, and included reduced water loss on rapid dehydration.In contrast to has2, has1 exhibited only minor changes in susceptibility to Dickeya dadantii despite similar ABA-hypersensitivity, indicating that crosstalk between ABA responses to this pathogen and drought stress can occur through more than one point in the signalling pathway.

View Article: PubMed Central - PubMed

Affiliation: Institut Jean-Pierre Bourgin, UMR1318, INRA, AgroParisTech, Versailles, France.

ABSTRACT
On water deficit, abscisic acid (ABA) induces stomata closure to reduce water loss by transpiration. To identify Arabidopsis thaliana mutants which transpire less on drought, infrared thermal imaging of leaf temperature has been used to screen for suppressors of an ABA-deficient mutant (aba3-1) cold-leaf phenotype. Three novel mutants, called hot ABA-deficiency suppressor (has), have been identified with hot-leaf phenotypes in the absence of the aba3 mutation. The defective genes imparted no apparent modification to ABA production on water deficit, were inherited recessively and enhanced ABA responses indicating that the proteins encoded are negative regulators of ABA signalling. All three mutants showed ABA-hypersensitive stomata closure and inhibition of root elongation with little modification of growth and development in non-stressed conditions. The has2 mutant also exhibited increased germination inhibition by ABA, while ABA-inducible gene expression was not modified on dehydration, indicating the mutated gene affects early ABA-signalling responses that do not modify transcript levels. In contrast, weak ABA-hypersensitivity relative to mutant developmental phenotypes suggests that HAS3 regulates drought responses by both ABA-dependent and independent pathways. has1 mutant phenotypes were only apparent on stress or ABA treatments, and included reduced water loss on rapid dehydration. The HAS1 locus thus has the required characteristics for a targeted approach to improving resistance to water deficit. In contrast to has2, has1 exhibited only minor changes in susceptibility to Dickeya dadantii despite similar ABA-hypersensitivity, indicating that crosstalk between ABA responses to this pathogen and drought stress can occur through more than one point in the signalling pathway.

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has mutants show ABA-hypersensitivity compared to wild-type.A, Induction of stomatal closure by ABA in wild-type and has mutants. Stomata aperture ratios (width/length) were measured after a 2 h pre-treatment in the light in stomata opening solution followed by a 3 h incubation with or without ABA at the concentrations indicated. Data are means ± SE of 3 independent experiments with 40 apertures measured per experiment and condition. Significance in Student t-tests comparing samples with and without ABA for the same genotype; **, p<1% or ***, p<0.1% level. B, ABA inhibition of root growth. Primary root length of 13 d old seedlings grown in long day photoperiod ABA was included in the growth media at the concentrations indicated. Error bars represent SE values (n = 24). Results presented are representative of those obtained in 2 independent experiments. C, ABA inhibition of seed germination after 7 d at 25°C. ABA was included in the growth media at the concentrations indicated. Germination was determined from the number of seedlings with green cotyledons compared to the total number of seeds sown. Error bars represent SE values (n = 3). Results presented are representative of those obtained in 2 independent experiments. Significance in Student t-test when comparing mutant and wild-type at a given ABA concentration, p<0.1%, ***. WT, wild-type.
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pone-0020243-g006: has mutants show ABA-hypersensitivity compared to wild-type.A, Induction of stomatal closure by ABA in wild-type and has mutants. Stomata aperture ratios (width/length) were measured after a 2 h pre-treatment in the light in stomata opening solution followed by a 3 h incubation with or without ABA at the concentrations indicated. Data are means ± SE of 3 independent experiments with 40 apertures measured per experiment and condition. Significance in Student t-tests comparing samples with and without ABA for the same genotype; **, p<1% or ***, p<0.1% level. B, ABA inhibition of root growth. Primary root length of 13 d old seedlings grown in long day photoperiod ABA was included in the growth media at the concentrations indicated. Error bars represent SE values (n = 24). Results presented are representative of those obtained in 2 independent experiments. C, ABA inhibition of seed germination after 7 d at 25°C. ABA was included in the growth media at the concentrations indicated. Germination was determined from the number of seedlings with green cotyledons compared to the total number of seeds sown. Error bars represent SE values (n = 3). Results presented are representative of those obtained in 2 independent experiments. Significance in Student t-test when comparing mutant and wild-type at a given ABA concentration, p<0.1%, ***. WT, wild-type.

Mentions: As the increased leaf temperature in the has mutants did not result from either increased ABA accumulation, reduced stomata density or reduced dissipation of heat due to altered photosynthetic capacity, the response of stomata to ABA was examined. After 5 h in the light in stomata opening solution has mutant and wild-type stomata opened to the same extent (Figure 6A; Figure S6). Low ABA concentrations resulted in a limited reduction in stomata aperture for wild-type that was not significantly different from untreated stomata (Figure 6A). In contrast, all three mutants showed a significant reduction in stomata aperture in the presence of ABA, with has1 and has2 being more ABA-hypersensitive. At high ABA concentrations wild-type showed the expected reduction in stomatal aperture, but closure was no longer significantly different in has mutants (Figure S6). An increased response of stomata to low ABA concentrations would be expected to result in elevated leaf temperatures and improved drought resistance on water deficit.


New ABA-hypersensitive Arabidopsis mutants are affected in loci mediating responses to water deficit and Dickeya dadantii infection.

Plessis A, Cournol R, Effroy D, Silva Pérez V, Botran L, Kraepiel Y, Frey A, Sotta B, Cornic G, Leung J, Giraudat J, Marion-Poll A, North HM - PLoS ONE (2011)

has mutants show ABA-hypersensitivity compared to wild-type.A, Induction of stomatal closure by ABA in wild-type and has mutants. Stomata aperture ratios (width/length) were measured after a 2 h pre-treatment in the light in stomata opening solution followed by a 3 h incubation with or without ABA at the concentrations indicated. Data are means ± SE of 3 independent experiments with 40 apertures measured per experiment and condition. Significance in Student t-tests comparing samples with and without ABA for the same genotype; **, p<1% or ***, p<0.1% level. B, ABA inhibition of root growth. Primary root length of 13 d old seedlings grown in long day photoperiod ABA was included in the growth media at the concentrations indicated. Error bars represent SE values (n = 24). Results presented are representative of those obtained in 2 independent experiments. C, ABA inhibition of seed germination after 7 d at 25°C. ABA was included in the growth media at the concentrations indicated. Germination was determined from the number of seedlings with green cotyledons compared to the total number of seeds sown. Error bars represent SE values (n = 3). Results presented are representative of those obtained in 2 independent experiments. Significance in Student t-test when comparing mutant and wild-type at a given ABA concentration, p<0.1%, ***. WT, wild-type.
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Related In: Results  -  Collection

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pone-0020243-g006: has mutants show ABA-hypersensitivity compared to wild-type.A, Induction of stomatal closure by ABA in wild-type and has mutants. Stomata aperture ratios (width/length) were measured after a 2 h pre-treatment in the light in stomata opening solution followed by a 3 h incubation with or without ABA at the concentrations indicated. Data are means ± SE of 3 independent experiments with 40 apertures measured per experiment and condition. Significance in Student t-tests comparing samples with and without ABA for the same genotype; **, p<1% or ***, p<0.1% level. B, ABA inhibition of root growth. Primary root length of 13 d old seedlings grown in long day photoperiod ABA was included in the growth media at the concentrations indicated. Error bars represent SE values (n = 24). Results presented are representative of those obtained in 2 independent experiments. C, ABA inhibition of seed germination after 7 d at 25°C. ABA was included in the growth media at the concentrations indicated. Germination was determined from the number of seedlings with green cotyledons compared to the total number of seeds sown. Error bars represent SE values (n = 3). Results presented are representative of those obtained in 2 independent experiments. Significance in Student t-test when comparing mutant and wild-type at a given ABA concentration, p<0.1%, ***. WT, wild-type.
Mentions: As the increased leaf temperature in the has mutants did not result from either increased ABA accumulation, reduced stomata density or reduced dissipation of heat due to altered photosynthetic capacity, the response of stomata to ABA was examined. After 5 h in the light in stomata opening solution has mutant and wild-type stomata opened to the same extent (Figure 6A; Figure S6). Low ABA concentrations resulted in a limited reduction in stomata aperture for wild-type that was not significantly different from untreated stomata (Figure 6A). In contrast, all three mutants showed a significant reduction in stomata aperture in the presence of ABA, with has1 and has2 being more ABA-hypersensitive. At high ABA concentrations wild-type showed the expected reduction in stomatal aperture, but closure was no longer significantly different in has mutants (Figure S6). An increased response of stomata to low ABA concentrations would be expected to result in elevated leaf temperatures and improved drought resistance on water deficit.

Bottom Line: The has2 mutant also exhibited increased germination inhibition by ABA, while ABA-inducible gene expression was not modified on dehydration, indicating the mutated gene affects early ABA-signalling responses that do not modify transcript levels.In contrast, weak ABA-hypersensitivity relative to mutant developmental phenotypes suggests that HAS3 regulates drought responses by both ABA-dependent and independent pathways. has1 mutant phenotypes were only apparent on stress or ABA treatments, and included reduced water loss on rapid dehydration.In contrast to has2, has1 exhibited only minor changes in susceptibility to Dickeya dadantii despite similar ABA-hypersensitivity, indicating that crosstalk between ABA responses to this pathogen and drought stress can occur through more than one point in the signalling pathway.

View Article: PubMed Central - PubMed

Affiliation: Institut Jean-Pierre Bourgin, UMR1318, INRA, AgroParisTech, Versailles, France.

ABSTRACT
On water deficit, abscisic acid (ABA) induces stomata closure to reduce water loss by transpiration. To identify Arabidopsis thaliana mutants which transpire less on drought, infrared thermal imaging of leaf temperature has been used to screen for suppressors of an ABA-deficient mutant (aba3-1) cold-leaf phenotype. Three novel mutants, called hot ABA-deficiency suppressor (has), have been identified with hot-leaf phenotypes in the absence of the aba3 mutation. The defective genes imparted no apparent modification to ABA production on water deficit, were inherited recessively and enhanced ABA responses indicating that the proteins encoded are negative regulators of ABA signalling. All three mutants showed ABA-hypersensitive stomata closure and inhibition of root elongation with little modification of growth and development in non-stressed conditions. The has2 mutant also exhibited increased germination inhibition by ABA, while ABA-inducible gene expression was not modified on dehydration, indicating the mutated gene affects early ABA-signalling responses that do not modify transcript levels. In contrast, weak ABA-hypersensitivity relative to mutant developmental phenotypes suggests that HAS3 regulates drought responses by both ABA-dependent and independent pathways. has1 mutant phenotypes were only apparent on stress or ABA treatments, and included reduced water loss on rapid dehydration. The HAS1 locus thus has the required characteristics for a targeted approach to improving resistance to water deficit. In contrast to has2, has1 exhibited only minor changes in susceptibility to Dickeya dadantii despite similar ABA-hypersensitivity, indicating that crosstalk between ABA responses to this pathogen and drought stress can occur through more than one point in the signalling pathway.

Show MeSH
Related in: MedlinePlus