Nitric Oxide Elicitation Induces the Accumulation of Secondary Metabolites and Antioxidant Defense in Adventitious Roots ofEchinacea purpurea

Abstract

Nitric oxide and reactive oxygen species are important signal molecules that play key roles in plant defense responses. We investigated the involvement of nitric oxide elicitation in the synthesis of secondary metabolites within the adventitious roots of Echinacea purpurea. When roots were treated with 100 I~M sodium nitroprusside (SNP), an exogenous nitric oxide producer, the accumulation of phenolics, flavonoids, and caffeic acid derivatives was enhanced. This level of SNP also induced an antioxidant defense, as indicated by increases in superoxide dismutase, ascorbate peroxidase, and ascorbic acid, along with decreases in hydrogen peroxide, lipid peroxidation, and dehydroascorbate/ascorbic acid. However, a higher concentration (250 ~M SNIP) acted as a pro-oxidant, thereby raising the levels of hydrogen peroxide, lipid peroxidation, and dehydroascorbate/ascorbic acid while diminishing ascorbic acid, ascorbate peroxidase, and the accumulation of secondary metabolites compared with our observations at 100 BM SNR Therefore, we conclude that eliciting E. purpurea adventitious roots with a concentration of 100 ~M SNP is beneficial to their accumulation of secondary metabolites. Keywords: antioxidant defense, bioreactor, Echinacea purpurea, elicitation, nitric oxide, secondary metabolitesThe production of secondary metabolites via plant cell/ organ cultures is an important area of investigation because of their commercial and medicinal importance. However, these compounds exist at only very low concentrations in plants, which limits their yields. Plant cells respond to various biotic and abiotic elicitors by activating a wide array of reactions [viz., ion fluxes across the plasma membrane, synthesis of reactive oxygen species (ROS), and phosphorylation and dephosphorylation of proteins]. These are all putative components of signal transduction pathways that lead to elicitor-induced defense responses, e.g., the activation of defense genes and hypersensitive cell death (Dietrich et al., 1990; N(~rnberger et al., 1994;Baker and Orlandi, 1995). It has been suggested that ROS alone cannot mediate a sufficient disease resistance response in plants, but in combination with nitric oxide (NO) can function synergistically to activate a stronger response (Wang and Wu, 2005). Therefore, NO is a diffusible, bioactive signalling molecule (Beligni and Lamattina, 2000;Neill et al., 2003; RomeroPuertas et al., 2004).The synthesis of secondary metabolites in plants is believed to be part of their defense response against biotic (pathogenic attack) and abiotic stresses. Applying the elicitors obtained from microorganisms (fungi and bacteria) is an effective strategy for improving the productivity of seconclary metabolites in plant cell/organ cultures (Roberts and Shuler, 1997). The generation of NO is a hallmark of such responses to fungal elicitors (Delledonne et al., 1998;Durner et al., 1998). NO has multiple functions, e.g., the stimulation of seed germination (Sarath et al., 2006), formation of adventitious roots (Pagnussat et al....

Effects associated with insertion of cryptogein gene utilizing Ri and Ti plasmids on morphology and secondary metabolites are stable in Bacopa monnieri-transformed plants grown in vitro and ex vitro

“…The crypt gene both under the constitutive promoter (Chaudhuri et al 2009;Majumdar et al 2012) and under the inducible promoter (Vuković et al 2013) was shown to be effective in increasing growth in crypt-transformed cultures. Other chemical inducers of plant defenses have also been reported to stimulate growth (Dörnenburg and Knorr 1995;Walker et al 2002;Wu et al 2007), which might be a generalized response to stress (Chaudhuri et al 2009). Since metabolite production is a function of concentration and biomass accumulation, the stimulatory effect of crypt on growth could result in significant enhancement in production of secondary metabolites in transformed cultures (Chaudhuri et al 2009).…”

Effect of Gibberellic Acid on Production of Biomass, Polyphenolics and Steviol Glycosides in Adventitious Root Cultures of Stevia rebaudiana (Bert.)

“…Currently, about 100,000 compounds have been identified in plants and about 4000 new compounds are discovered each year [19]. A wide variety of chemicals have been obtained from plants, including ginsenosides, paclitaxel, echinacosides, shikonin, berberine and hypericin [20][21][22][23]. These compounds are involved in the elimination of toxic free radicals, enzyme activation, activation of immune system, controlling the expression of genes and cell death initiation [24,25].…”

Protective Effect of Nitric Oxide against Oxidative Damage in Arabidopsis Leaves under Ultraviolet-B Irradiation

“…In the plant kingdom, this important signal can be used instead of red light to induce germination (Beligni and Lamattina 2001), and it can also affect growth and development (Durner and Klessing 1999) and enhance cell senescence . NO can also mediate plant responses to biotic and abiotic stresses, e.g., drought, salt, and heat; diseases; and apoptosis (Leshem et al 1998;Durner and Klessing 1999;Beligni and Lamattina 2001;Mata and Lamattina 2001;Zhao et al 2004;Wu et al 2007). It is synthesized by NO synthase (NOS) in animals and plants.…”