Exogenous nitric oxide application results in the modification of the antioxidant status of Medicago truncatula plants
Date Issued
2010
Abstract
Nitric oxide (NO) is a bioactive molecule involved in numerous biological events that has
been reported to display both prooxidant and antioxidant properties in plants. Several
reports exist which demonstrate the protective action of sodium nitroprusside (SNP), a
NO donor [1], which acts as a signal molecule in plants responsible for the regulation of
the expression of many antioxidant enzymes. Preliminary analyses were carried out in
order to determine the optimal method of SNP application. This study subsequently
attempted to provide novel insight into the effect of application of low (lOOIlM) and high
(2.5mM) concentrations of SNP on mature (40 day) and senescing (65 day) Medicago
truncatufa plants following a combined physiological, biochemical and molecular
approach. Higher concentrations of SNP resulted in increased cellular damage levels,
reactive oxygen species (ROS) concentration and polyamine content, further induced in
older tissues. Quantitative real-time PCR data examining antioxidant gene expression
levels suggest that low concentration of exogenous NO applied in mature leaves leads to
an overall induction of antioxidant gene expression, while increasing concentration results
in suppression of these genes. Conversely, older plants demonstrate a much more variable
regulation which appears to be time-dependent. Overall, senescing M truncatufa plants
demonstrated greater sensitivity to NO-induced oxidative damage, suggesting a
developmental stage-dependent suppression in the plant's capacity to cope with free
oxygen and nitrogen radicals.
been reported to display both prooxidant and antioxidant properties in plants. Several
reports exist which demonstrate the protective action of sodium nitroprusside (SNP), a
NO donor [1], which acts as a signal molecule in plants responsible for the regulation of
the expression of many antioxidant enzymes. Preliminary analyses were carried out in
order to determine the optimal method of SNP application. This study subsequently
attempted to provide novel insight into the effect of application of low (lOOIlM) and high
(2.5mM) concentrations of SNP on mature (40 day) and senescing (65 day) Medicago
truncatufa plants following a combined physiological, biochemical and molecular
approach. Higher concentrations of SNP resulted in increased cellular damage levels,
reactive oxygen species (ROS) concentration and polyamine content, further induced in
older tissues. Quantitative real-time PCR data examining antioxidant gene expression
levels suggest that low concentration of exogenous NO applied in mature leaves leads to
an overall induction of antioxidant gene expression, while increasing concentration results
in suppression of these genes. Conversely, older plants demonstrate a much more variable
regulation which appears to be time-dependent. Overall, senescing M truncatufa plants
demonstrated greater sensitivity to NO-induced oxidative damage, suggesting a
developmental stage-dependent suppression in the plant's capacity to cope with free
oxygen and nitrogen radicals.
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