including MYB family transcription factors and protein kinases are regulated through
S-nitrosylation. It can also trigger several redox-based signaling while altering expression of several genes involved in plant defense. NO upregulated the activity and
transcription of APX and GR, the two key enzymes in the ascorbic acid-glutathione
(AsA-GSH) cycle in Nicotiana tabacum and Cucumis sativus leaves, and conferred
resistance to abiotic stress [93].
It has been reported that even mild water deficit also leads to the accumulation
of NO in cucumber roots [2]. Moreover, accumulation of NO as a result of application of exogenous donors in many reported studies also correlated well with the
amelioration of drought stress, while the use of NO scavengers/inhibitors reversed
this effect [68]. Exogenous NO improved drought tolerance by reducing stomatal
opening, membrane damage, and lipid peroxidation in water-stressed plants [2].
Application of SNP enhanced plant tolerance to drought by inducing stomatal
closure, reducing transpiration rate, thereby lowering water loss in leaves and protein
synthesis, enhancing photosynthesis rate, and increasing the activities of ROSscavenging enzymes [69].A good number of studies confirmed the generation of
NO in guard cells in response to drought and ABA by using a NO-sensitive
fluorescent dye DAF-2DA [70]. The increase in NO production under drought stress
has been correlated significantly to the decrease in stomatal conductance in Vitis
vinifera. Additionally, NO decreased drought-induced reduction in photochemical
quenching during adventitious rooting in explants of Tagetes erecta [71]. Similarly,
NO-treated Dendrobium huoshanense plants maintained high levels of antioxidant
enzyme activities and less lipid peroxidation under drought stress [2]. Not only that,
NO also help in maintaining high vacuolar concentrations of osmotically active
solutes and amino acids under drought. NO promoted drought-induced free proline
accumulation in Oryza sativa, Ginkgo biloba, and Triticum aestivum [72]. Similarly,
accumulation of glycine betaine was also promoted by NO-mediated stimulation
of betaine aldehyde dehydrogenase activity in the leaves of drought-stressed Zea
mays [72]. Moreover, transgenic plants overexpressing the rat neural nitric oxide
synthase gene in A. thaliana and O. sativa exhibit enhanced drought tolerance than
their respective untransformed controls [2, 20].
More than 45 million hectares of cultivated land globally has been contaminated
with high salinity limiting the plant water and mineral uptake. Previous research
suggested that exogenous application of NO donors could enhance salinity tolerance
in a number of plant species including Phragmites communis, Lupinus luteus,
tobacco, sunflower, cucumber, wheat, and rice [73, 74, 76, 77]. In most cases, an
enhancement of endogenous NO levels is followed by Na
+ exclusion and improved
K
+
/Na
+ ratios. On the other hand, Arabidopsis noa1 mutant with lower NO level was
more sensitive to NaCl further supporting the need of NO in salinity tolerance.
Further SNP-induced antioxidant enzymes provided resistance to salt stress by
alleviating the oxidative damage in many plant species including rice seedlings,
cucumber, maize, etc. [73, 74, 76]. Besides, NO participates in enhancement of
photosynthesis by inducing the photosynthetic pigments and adenosine triphosphate
synthesis, by quenching excess energy, and by increasing in quantum yield of PSII
by using exogenous NO in Solanum melongena seedlings under salt stress [75, 77].
606
P. Santisree et al.
S-nitrosylation. It can also trigger several redox-based signaling while altering expression of several genes involved in plant defense. NO upregulated the activity and
transcription of APX and GR, the two key enzymes in the ascorbic acid-glutathione
(AsA-GSH) cycle in Nicotiana tabacum and Cucumis sativus leaves, and conferred
resistance to abiotic stress [93].
It has been reported that even mild water deficit also leads to the accumulation
of NO in cucumber roots [2]. Moreover, accumulation of NO as a result of application of exogenous donors in many reported studies also correlated well with the
amelioration of drought stress, while the use of NO scavengers/inhibitors reversed
this effect [68]. Exogenous NO improved drought tolerance by reducing stomatal
opening, membrane damage, and lipid peroxidation in water-stressed plants [2].
Application of SNP enhanced plant tolerance to drought by inducing stomatal
closure, reducing transpiration rate, thereby lowering water loss in leaves and protein
synthesis, enhancing photosynthesis rate, and increasing the activities of ROSscavenging enzymes [69].A good number of studies confirmed the generation of
NO in guard cells in response to drought and ABA by using a NO-sensitive
fluorescent dye DAF-2DA [70]. The increase in NO production under drought stress
has been correlated significantly to the decrease in stomatal conductance in Vitis
vinifera. Additionally, NO decreased drought-induced reduction in photochemical
quenching during adventitious rooting in explants of Tagetes erecta [71]. Similarly,
NO-treated Dendrobium huoshanense plants maintained high levels of antioxidant
enzyme activities and less lipid peroxidation under drought stress [2]. Not only that,
NO also help in maintaining high vacuolar concentrations of osmotically active
solutes and amino acids under drought. NO promoted drought-induced free proline
accumulation in Oryza sativa, Ginkgo biloba, and Triticum aestivum [72]. Similarly,
accumulation of glycine betaine was also promoted by NO-mediated stimulation
of betaine aldehyde dehydrogenase activity in the leaves of drought-stressed Zea
mays [72]. Moreover, transgenic plants overexpressing the rat neural nitric oxide
synthase gene in A. thaliana and O. sativa exhibit enhanced drought tolerance than
their respective untransformed controls [2, 20].
More than 45 million hectares of cultivated land globally has been contaminated
with high salinity limiting the plant water and mineral uptake. Previous research
suggested that exogenous application of NO donors could enhance salinity tolerance
in a number of plant species including Phragmites communis, Lupinus luteus,
tobacco, sunflower, cucumber, wheat, and rice [73, 74, 76, 77]. In most cases, an
enhancement of endogenous NO levels is followed by Na
+ exclusion and improved
K
+
/Na
+ ratios. On the other hand, Arabidopsis noa1 mutant with lower NO level was
more sensitive to NaCl further supporting the need of NO in salinity tolerance.
Further SNP-induced antioxidant enzymes provided resistance to salt stress by
alleviating the oxidative damage in many plant species including rice seedlings,
cucumber, maize, etc. [73, 74, 76]. Besides, NO participates in enhancement of
photosynthesis by inducing the photosynthetic pigments and adenosine triphosphate
synthesis, by quenching excess energy, and by increasing in quantum yield of PSII
by using exogenous NO in Solanum melongena seedlings under salt stress [75, 77].
606
P. Santisree et al.