Nitric oxide regulates proline and polyamine biosynthesis in medicatgo truncatula plants
Date Issued
July 2011
Abstract
Nitric oxide (NO) is a bioactive molecule involved in numerous biological events that has been
reported to act as a signalling molecule regulating a variety of key processes in plants. The present
study attempts to examine the effect of application of low (100~) and high (2.5mM)
concentrations of sodium nitroprusside (SNP), a NO donor, on the biosynthesis of proline and
polyamines, which are known to confer protective characteristics to plants under stress conditions.
Analyses were carried out in two developmental stages of Medicago plants (mature and
senescing). Spectrophotometric and chromatographic approaches revealed that higher
concentrations of SNP induced significant increases in proline and putrescine content following
SNP application in both mature and senescing leaves (further induced in older tissues), although
spermidine and spermine levels remained unaltered. Increases in proline and putrescine content
were supported by increased activities of biosynthetic enzymes P5CS and ADC respectively,
although ODC activity displayed similar patterns to control samples. Quantitative real-time RTPCR
data examining proline and polyamine biosynthetic gene (P5CS, ADC, ODC, SPMS, SPDS,
SAMDC) expression levels suggest that NO plays a key role in the regulation of the relevant
transcriptional pathways. Overall, strong evidence suggests that nitric oxide regulates key
protective metabolite levels in plants via enzymatic and transcriptional modulation of proline and
polyamine biosynthesis pathways, thus potentially improving the plant's capacity to cope with
free oxygen and nitrogen radicals.
reported to act as a signalling molecule regulating a variety of key processes in plants. The present
study attempts to examine the effect of application of low (100~) and high (2.5mM)
concentrations of sodium nitroprusside (SNP), a NO donor, on the biosynthesis of proline and
polyamines, which are known to confer protective characteristics to plants under stress conditions.
Analyses were carried out in two developmental stages of Medicago plants (mature and
senescing). Spectrophotometric and chromatographic approaches revealed that higher
concentrations of SNP induced significant increases in proline and putrescine content following
SNP application in both mature and senescing leaves (further induced in older tissues), although
spermidine and spermine levels remained unaltered. Increases in proline and putrescine content
were supported by increased activities of biosynthetic enzymes P5CS and ADC respectively,
although ODC activity displayed similar patterns to control samples. Quantitative real-time RTPCR
data examining proline and polyamine biosynthetic gene (P5CS, ADC, ODC, SPMS, SPDS,
SAMDC) expression levels suggest that NO plays a key role in the regulation of the relevant
transcriptional pathways. Overall, strong evidence suggests that nitric oxide regulates key
protective metabolite levels in plants via enzymatic and transcriptional modulation of proline and
polyamine biosynthesis pathways, thus potentially improving the plant's capacity to cope with
free oxygen and nitrogen radicals.
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