Nitric oxide in plants: the biosynthesis and cell signalling properties of a fascinating molecule

Cross-talk between calcium-calmodulin and nitric oxide in abscisic acid signaling in leaves of maize plants

“…This enzyme catalyzes the oxygen-and NADPHdependent oxidation of l-arginine to l-citrulline and NO in a complex reaction requiring FAD, FMN, BH 4 , Ca 2+ , and CaM [12,14,17,18]. In plants, pharmacological, biochemical and physicochemical, and immunological evidence indicates the presence of NOS-like activity similar, to a certain extent, to mammalian NOS [12,14,17,18,[22][23][24], although no plant NOS similar to the mammalian one has been characterized [19][20][21]. It has been shown that NOS is localized in the cytoplasm, chloroplasts, mitochondria, peroxisomes, and nucleus in plant cells [14,22,24,44].…”

“…NO has also been shown to induce an increase in the concentration of [Ca 2+ ] i in plant cells. NO may mobilize Ca 2+ from internal stores through the activation of ryanodine receptor (RYR)-like channels [15,17,40,41,[46][47][48] and plasma membrane Ca 2+ -permeable channels [40,41,47]. In the present study, our data showed that NO induced not only an increase in [Ca 2+ ] i in the protoplasts of maize leaves, which was sensitive to the plasma membrane Ca 2+ channel blocker LaCl 3 ( Figure 4A), but also increases in the expression of CaM1 ( Figure 5A) and the content of CaM in leaves of maize plants ( Figure 5B).…”

“…An increasing body of evidence indicates that NO, which was first identified as a unique diffusible molecular messenger in animals, plays important roles in various physiological processes in plants, including defense responses and programmed cell death (PCD), hormone responses, abiotic stress, root and xylem development, germination, iron homeostasis, and flowering [12][13][14][15][16][17][18]. In mammals, NO is formed exclusively by the enzyme nitric oxide synthase (NOS).…”

“…In mammals, NO is formed exclusively by the enzyme nitric oxide synthase (NOS). NOS catalyzes the conversion of l-arginine into lcitrulline and NO in the presence of molecular oxygen [12,14,17,18]. Three isoforms of NOS have been identified in mammalian species: neuronal NOS (nNOS), endothelial [12,15,18].…”

“…In plants, there are several potential sources of NO, including NOS-like enzyme, nitrate reductase (NR), and non-enzymatic sources [12,14,15,17]. Although no plant NOS similar to the mammalian one has been identified [19][20][21], several lines of evidence have demonstrated the presence of NOS-like activity in plant cells [12,14,17,18,[22][23][24]. The NOS activity in pea leaf peroxisomes has been biochemically characterized, which is strictly dependent on l-arginine, NADPH, tetrahydrobiopterin (BH 4 ), and CaM, and requires Ca 2+ [22].…”