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OXI1 protein kinase is required for plant immunity against Pseudomonas syringae in Arabidopsis.

Petersen LN, Ingle RA, Knight MR, Denby KJ - J. Exp. Bot. (2009)

Bottom Line: Null oxi1 mutants are more susceptible to both virulent and avirulent strains of the biotrophic bacterial pathogen Pseudomonas syringae compared with the wild type, indicating that OXI1 positively regulates both basal resistance triggered by the recognition of pathogen-associated molecular patterns, as well as effector-triggered immunity.The induction of OXI1 after P. syringae infection spatially and temporally correlates with the oxidative burst.Furthermore, induction is reduced in atrbohD mutants and after application of DPI (an inhibitor of NADPH oxidases) suggesting that reactive oxygen species produced through NADPH oxidases drives OXI1 expression during this plant-pathogen interaction.

View Article: PubMed Central - PubMed

Affiliation: Department of Molecular and Cell Biology, University of Cape Town, Private Bag, Rondebosch 7701, South Africa.

ABSTRACT
Expression of the Arabidopsis Oxidative Signal-Inducible1 (OXI1) serine/threonine protein kinase gene (At3g25250) is induced by oxidative stress. The kinase is required for root hair development and basal defence against the oomycete pathogen Hyaloperonospora parasitica, two separate H(2)O(2)-mediated processes. In this study, the role of OXI1 during pathogenesis was characterized further. Null oxi1 mutants are more susceptible to both virulent and avirulent strains of the biotrophic bacterial pathogen Pseudomonas syringae compared with the wild type, indicating that OXI1 positively regulates both basal resistance triggered by the recognition of pathogen-associated molecular patterns, as well as effector-triggered immunity. The level of OXI1 expression appears to be critical in mounting an appropriate defence response since OXI1 overexpressor lines also display increased susceptibility to biotrophic pathogens. The induction of OXI1 after P. syringae infection spatially and temporally correlates with the oxidative burst. Furthermore, induction is reduced in atrbohD mutants and after application of DPI (an inhibitor of NADPH oxidases) suggesting that reactive oxygen species produced through NADPH oxidases drives OXI1 expression during this plant-pathogen interaction.

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Related in: MedlinePlus

Expression of defence associated genes in the oxi1 mutant. Three-week-old Ws-2 and the oxi1 mutant were pressure-inoculated with either 10 mM MgCl2 alone (–) or 5×105 cfu ml−1 avirulent Pst DC3000 avrB (avrB) or virulent Pst DC3000 (Pst) in a 10 mM MgCl2 suspension. Leaves were harvested before the start of the experiment (0) or at various time points post-infection as indicated. Expression of PR-1 (A) and VSP1 (B) was assessed via Northern analysis. Ethidium bromide- (A) and methylene blue- (B) stained RNA were used as loading controls. Results shown are for one representative experiment of two.
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fig4: Expression of defence associated genes in the oxi1 mutant. Three-week-old Ws-2 and the oxi1 mutant were pressure-inoculated with either 10 mM MgCl2 alone (–) or 5×105 cfu ml−1 avirulent Pst DC3000 avrB (avrB) or virulent Pst DC3000 (Pst) in a 10 mM MgCl2 suspension. Leaves were harvested before the start of the experiment (0) or at various time points post-infection as indicated. Expression of PR-1 (A) and VSP1 (B) was assessed via Northern analysis. Ethidium bromide- (A) and methylene blue- (B) stained RNA were used as loading controls. Results shown are for one representative experiment of two.

Mentions: As OXI1 is required for resistance against at least two biotrophic pathogens, an attempt was made to establish a functional basis for this requirement. However, expression of the classic defence gene PR-1 was not compromised in the oxi1 mutant following infection with avirulent P. syringae (Fig. 4A; see Supplementary Fig. S4A at JXB online). Given that OXI1 is required for full activation of MPK3 amd MPK6 in response to ROS and cellulase treatment (Rentel et al., 2004), it was investigated whether OXI1 regulates the expression of MPK6-dependent Vegetative Storage Protein1 (VSP1) in response to pathogen challenge. VSP1 was induced only 48 h after infection with virulent P. syringae, again this induction was not affected in the oxi1 mutant (Fig. 4B; see Supplementary Fig. S4B at JXB online). As expected, VSP1 was not induced in response to challenge with avirulent P. syringae in either wild-type or oxi1 mutant plants (data not shown).


OXI1 protein kinase is required for plant immunity against Pseudomonas syringae in Arabidopsis.

Petersen LN, Ingle RA, Knight MR, Denby KJ - J. Exp. Bot. (2009)

Expression of defence associated genes in the oxi1 mutant. Three-week-old Ws-2 and the oxi1 mutant were pressure-inoculated with either 10 mM MgCl2 alone (–) or 5×105 cfu ml−1 avirulent Pst DC3000 avrB (avrB) or virulent Pst DC3000 (Pst) in a 10 mM MgCl2 suspension. Leaves were harvested before the start of the experiment (0) or at various time points post-infection as indicated. Expression of PR-1 (A) and VSP1 (B) was assessed via Northern analysis. Ethidium bromide- (A) and methylene blue- (B) stained RNA were used as loading controls. Results shown are for one representative experiment of two.
© Copyright Policy - open-access
Related In: Results  -  Collection

License 1 - License 2
Show All Figures
getmorefigures.php?uid=PMC2736892&req=5

fig4: Expression of defence associated genes in the oxi1 mutant. Three-week-old Ws-2 and the oxi1 mutant were pressure-inoculated with either 10 mM MgCl2 alone (–) or 5×105 cfu ml−1 avirulent Pst DC3000 avrB (avrB) or virulent Pst DC3000 (Pst) in a 10 mM MgCl2 suspension. Leaves were harvested before the start of the experiment (0) or at various time points post-infection as indicated. Expression of PR-1 (A) and VSP1 (B) was assessed via Northern analysis. Ethidium bromide- (A) and methylene blue- (B) stained RNA were used as loading controls. Results shown are for one representative experiment of two.
Mentions: As OXI1 is required for resistance against at least two biotrophic pathogens, an attempt was made to establish a functional basis for this requirement. However, expression of the classic defence gene PR-1 was not compromised in the oxi1 mutant following infection with avirulent P. syringae (Fig. 4A; see Supplementary Fig. S4A at JXB online). Given that OXI1 is required for full activation of MPK3 amd MPK6 in response to ROS and cellulase treatment (Rentel et al., 2004), it was investigated whether OXI1 regulates the expression of MPK6-dependent Vegetative Storage Protein1 (VSP1) in response to pathogen challenge. VSP1 was induced only 48 h after infection with virulent P. syringae, again this induction was not affected in the oxi1 mutant (Fig. 4B; see Supplementary Fig. S4B at JXB online). As expected, VSP1 was not induced in response to challenge with avirulent P. syringae in either wild-type or oxi1 mutant plants (data not shown).

Bottom Line: Null oxi1 mutants are more susceptible to both virulent and avirulent strains of the biotrophic bacterial pathogen Pseudomonas syringae compared with the wild type, indicating that OXI1 positively regulates both basal resistance triggered by the recognition of pathogen-associated molecular patterns, as well as effector-triggered immunity.The induction of OXI1 after P. syringae infection spatially and temporally correlates with the oxidative burst.Furthermore, induction is reduced in atrbohD mutants and after application of DPI (an inhibitor of NADPH oxidases) suggesting that reactive oxygen species produced through NADPH oxidases drives OXI1 expression during this plant-pathogen interaction.

View Article: PubMed Central - PubMed

Affiliation: Department of Molecular and Cell Biology, University of Cape Town, Private Bag, Rondebosch 7701, South Africa.

ABSTRACT
Expression of the Arabidopsis Oxidative Signal-Inducible1 (OXI1) serine/threonine protein kinase gene (At3g25250) is induced by oxidative stress. The kinase is required for root hair development and basal defence against the oomycete pathogen Hyaloperonospora parasitica, two separate H(2)O(2)-mediated processes. In this study, the role of OXI1 during pathogenesis was characterized further. Null oxi1 mutants are more susceptible to both virulent and avirulent strains of the biotrophic bacterial pathogen Pseudomonas syringae compared with the wild type, indicating that OXI1 positively regulates both basal resistance triggered by the recognition of pathogen-associated molecular patterns, as well as effector-triggered immunity. The level of OXI1 expression appears to be critical in mounting an appropriate defence response since OXI1 overexpressor lines also display increased susceptibility to biotrophic pathogens. The induction of OXI1 after P. syringae infection spatially and temporally correlates with the oxidative burst. Furthermore, induction is reduced in atrbohD mutants and after application of DPI (an inhibitor of NADPH oxidases) suggesting that reactive oxygen species produced through NADPH oxidases drives OXI1 expression during this plant-pathogen interaction.

Show MeSH
Related in: MedlinePlus