Favouring NO over H2O2 production will increase Pb tolerance in Prosopis farcta via altered primary metabolism
Introduction
Lead (Pb), one of the most abundant globally distributed toxic elements, posing a significant risk to the health of humans, animals, and plants. At the whole-plant level, high concentration of Pb causes the disruption of physiological and biochemical processes like a decrease in photosynthesis, altered uptake of essential elements, inhibition of growth, lower biomass and yields (Ali et al., 2014, Arias et al., 2010). At the molecular level, Pb changes cell membrane permeability, reacts with active groups of different enzymes (for example, haem groups), reacts with phosphate groups of ADP or ATP (Pourrut et al., 2011). These results in negative effects are associated with oxidative damage to plant cell due to a compromised antioxidant defense machinery and the production of reactive oxygen species (ROS) (Verma and Dubey, 2003). However, despite their potential for causing harmful oxidations, it is now well established that ROS; and most often H2O2, may also function as signaling molecule (Zafari et al., 2016, Ali et al., 2014).
To cope with oxidative stress, plants have evolved two protective enzymatic and non-enzymatic mechanisms to detoxify ROS species. The former includes catalase (CAT: E.C.1.11.1.6.), ascorbate peroxidase (APX: E.C.1.11.1.11), guaiacol peroxidase (GPX: E.C.1.11.1.7) and the latter involves ascorbate and glutathione (Gill and Tuteja, 2010); which work in concert to detoxify ROS. The low-molecular-weight antioxidant ascorbate functions as redox buffer that reduces ROS. It is the well-known molecule in the detoxification of H2O2, particularly as a substrate of APX, and is fundamental component of the ascorbate-glutathione cycle, which is present in most cellular compartments (Smirnoff and Wheeler, 2000). Crucially, ascorbate can also acts as a metabolic interface to modulate the appropriate induction of acclimation responses (Foyer and Noctor, 2005).
ROS and potentially ascorbate contribute to mechanisms that allow plants to withstand abiotic stresses that could affect their vigour and survival (Mittler, 2017, Huang et al., 2010). In response to metals exposure, plants accumulate different metabolites to concentrations in the millimolar range, particularly phenolic and nitrogenous compounds such as amino acids and polyamines (Sharma and Dietz, 2006). Plant phenolics contribute to ROS quenching and are considered as parts of defensive mechanism (Dǔcić et al., 2008). Crucially phenylalanine ammonia-lyase (PAL) gene expression is inducible by ROS (Lin et al., 2005), and in heavy metal-treated plants leads to phenolic acid accumulation (Kováčik et al., 2009). Also, the accumulation of some amino acids such as proline may help in ameliorating of negative consequences of metal toxicity (Kováčik et al., 2010). These solutes are also sources of carbon and nitrogen during environmental challenges (Dubay and Pessarakli, 1995).
Polyamines including putrescine (Put), spermidine (Spd) and spermine (Spm) influence various processes in controlling plant growth and development. Due to the presence of positively charged groups, the interaction of polyamines with proteins, nucleic acids, membrane phospholipids, and cell wall constituents can activate or stabilize these molecules. As such polyamines contribute significantly in enhancing plant defense strategies in response to abiotic stresses including heavy metal (Groppa and Benavides, 2008).
Along with H2O2, the free radical NO has gained special interest in plant signaling pathways controlling processes that range from biotic and abiotic stress responses to growth and development (Mur et al., 2012). Numerous studies have reported NO and H2O2 induce profound changes in the expression, enzymes activities and metabolite levels in phenylpropanoid and nitrogen pathways employed as tolerance mechanisms (Gao et al., 2009, Iqbal et al., 2014). Similarly, we have recently shown that NO acts as a signal molecule mediating Pb-induced stress tolerance in Prosopis farcta; a perennial trees/shrub species well known for their resistance to heavy metals (Zafari et al., 2016). However, it is likely that the Prosopis response is not triggered by NO alone but is the result of a cross-talk between different signals and metabolic pathways, especially ROS-dependent ones. This current study applied ascorbic acid as a H2O2 scavenger to establish that NO and H2O2 interact to regulate metabolome changes in Prosopis conducting to Pb tolerance strategies.
Section snippets
Plant culture and treatments
Prosopis farcta L. seeds were scarified with 98% sulphuric acid and sterilized in a solution of sodium hypochlorite (2% w/v), and then thoroughly rinsed in distilled water. Seeds were incubated at 25 °C for 3 days to germinate. Germinated seeds were then transferred into plastic containers with 2.5 dm3 of half strength Hoagland nutrient solution (pH 6). Plants were kept at 27 (light) /22 °C (dark) with a 16 h light photoperiod (200 µmol m−2 s−1) and 60–80% air humidity. After 21 days, uniform
Pb and Asc contents and plant growth
To provide further insight into the mechanisms of ROS mediated tolerance against Pb in Prosopis farcta we examined the impact of co-application of the ROS scavenger. Fig. 1a shows how feeding Prospois with 400 µM Pb increased absorbed Pb content (68.5 mg/kg) but the Pb content in the Pb+Asc-treated plants was 32% lower. To confirm the effect of exogenous Asc application its endogenous content in different samples was measured. Results showed that the ascorbate levels in response to Pb application
Discussion
ROS are produced as inevitable by-products of several metabolic pathways. In order to avoid ROS toxicity, plants are provided with a flexible set of enzymes and metabolites involved in ROS catabolism, which frequently acts at ROS generation sites (Mittler et al., 2004). Despite much metabolic energy being consumed on ROS scavenging by plant cells, ROS are also actively generated by cellular metabolic processes linked to optimal growth conditions. This aligns with growing evidence suggests that
Author contribution
This research paper was accomplished with the collaboration of all authors. Somaieh Zafari performed the experiments, analyzed and interpreted data and wrote the manuscript. Mohsen Sharifi designed and supervised the study. Luis A. J. Mur helped to evaluate and edit the manuscript. Najme Ahmadian Chashmi was the study advisor.
Acknowledgments
The authors greatly appreciate Tarbiat Modares University for supporting this research.
References (75)
- et al.
Phenolic composition and biological activities of Salvia halophile and Salvia virgata from Turkey
Food Chem.
(2008) - et al.
Promotive role of 5-aminolevulinic acid on mineral nutrients and antioxidative defense system under lead toxicity in Brassica napus
Ind. Crop Prod.
(2014) - et al.
Effects of Glomus deserticola inoculation on Prosopis: enhancing chromium and lead uptake and translocation as confirmed by X-ray mapping, ICP-OES and TEM techniques
Environ. Exp. Bot.
(2010) - et al.
Exogenously applied ascorbic acid alleviates salt-induced oxidative stress in wheat
Environ. Exp. Bot.
(2008) - et al.
Nitric oxide: a non-traditional regulator of plant growth
Trends Plant Sci.
(2001) A rapid and sensitive method for the quantitation of microgram quantities of protein utilizing the principle of protein-dye binding
Anal. Biochem.
(1976)- et al.
Induction of shikimate dehydrogenase and peroxidase in pepper (Capsicum anuum L.) seedlings in response to copper stress and its relation to lignification
Plant Sci.
(2001) - et al.
Nitric oxide enhances salt tolerance in cucumber seedlings by regulating free polyamine content
Environ. Exp. Bot.
(2013) - et al.
Genetic modification of amino acid metabolism in woody plants
Plant Physiol. Biochem.
(2003) - et al.
Reactive oxygen species and antioxidant machinery in abiotic stress tolerance in crop plants
Plant Physiol. Biochem.
(2010)
Regulation of NAD- and NADP-dependent isocitrate dehydrogenases by reduction levels of pyridine nucleotides in mitochondria and cytosol of pea leaves
Biochim. Et. Biophys. Acta
A new perspective of phytohormones in salinity tolerance: regulation of proline metabolism
Environ. Exp. Bot.
Nitric oxide signals ROS scavenger-mediated enhancement of PAL activity in nitrogen-deficient Matricaria chamomilla roots: side effects of scavengers
Free Radic. Biol. Med.
Effect of copper and salicylic acid on phenolic metabolites and free amino acids in Scenedesmus quadricauda (Chlorophyceae)
Plant Sci.
Doubled CO could improve the drought tolerance better in sensitive cultivars than in tolerant cultivars in spring wheat
Plant Sci.
Hydrogen peroxide mediates defence responses induced by chitosans of different molecular weights in rice
J. Plant Physiol.
Relationship between osmotic stress and the levels of free, conjugated and bound polyamines in leaves of wheat seedlings
Plant Sci.
ROS are good
Trends Plant Sci.
Reactive oxygen gene network of plants
Trends Plant Sci.
Isolation, structure elucidation and antioxidant potential of the major phenolic and flavonoid compounds in brined olive drupes
Food Chem. Toxicol.
Spectrophotometric measurements of the enzymatic formation of fumaric and cis-aconitic acids
Biochim. Et. Biophys. Acta
Effect of chromium accumulation on photosynthetic pigments, oxidative stress defence system, nitrate reduction, proline level and eugenol content of Ocimum tenuiflorum L
Plant Sci.
Modulation of polyamine balance in Lotus glaber by salinity and arbuscular mycorrhiza
Plant Physiol. Biochem.
Regulatory metabolic networks in drought stress responses
Curr. Opin. Plant Biol.
Improved method for polyamine determination in TMV a rod-shaped virus
J. Virol. Methods
Oxidative stress and some antioxidant systems in acid rain-treated bean plants
Plant Sci.
Lead toxicity induces lipid peroxidation and alters the activities of antioxidant enzymes in growing rice plants
Plant Sci.
Modulation of Pb-induced stress in Prosopis shoots through an interconnected network of signaling molecules, phenolic compounds and amino acids
Plant Physiol. Biochem
Roles of hydroxyproline-rich glycoproteins in the pollen tube and style cell growth of tobacco (Nicotiana tabacum L.)
J. Plant Physiol.
Lignan enhancement in hairy root cultures of Linum album using coniferaldehyde and methylenedioxycinnamic acid
Prep. Biochem. Biotechnol.
A review of ascorbic acid potentialities against oxidative stress induced in plants
J. Agrobiol.
Involvement of polyamines in plant response to abiotic stress
Biotechnol. Lett.
Deciphering transcriptional and metabolic networks associated with lysine metabolism during Arabidopsis seed development
Plant Physiol.
Phenolics metabolism and lignin synthesis in root suspension cultures of Panax ginseng in response to copper stress
Plant Sci.
Rapid determination of free proline for water-stress studies
Plant Soil
Simultaneous analysis of the non-canonical amino acids norleucine and norvaline in biopharmaceutical-related fermentation processes by a new ultra-high performance liquid chromatography approach
Amino Acids
Magnesium deficiency and high light intensity enhance activities of superoxide dismutase, ascorbate peroxidase, and glutathione reductase in bean leaves
Plant Physiol.
Cited by (13)
Full-length transcriptome sequencing of the short-rotation woody crop Salix integra reveals a time series response to Pb stress
2023, Industrial Crops and ProductsNitric oxide donor, sodium nitroprusside modulates hydrogen sulfide metabolism and cysteine homeostasis to aid the alleviation of chromium toxicity in maize seedlings (Zea mays L.)
2022, Journal of Hazardous MaterialsCitation Excerpt :Phytoremediation approaches of Cr involve different mechanisms (Sharma et al., 2021). This includes the exogenous supply of NO to mitigate heavy metals-induced phytotoxicity (Corpas and Barroso, 2015; Zafari et al., 2017; Shivaraj et al., 2020). The present study, which fits perfectly with the protection of agronomic plants against the harmful effects of Cr, would provide new data useful to (i) tackle this environmental issue and (ii) deeper characterize NO utilization for heavy metal remediation.
Uptake and phytotoxicity of lead are affected by nitrate nutrition and phenolic metabolism
2020, Environmental and Experimental BotanyCitation Excerpt :However, Pb-stimulated ROS formation may be lower compared to other metals even after higher dose (0.1 mM) when tested in the green microalga (Kováčik et al., 2017). Other ROS such as H2O2 were significantly stimulated only by higher Pb doses such as 4 mM in wheat (Yang et al., 2010) or 0.4 mM in Prosopis (Zafari et al., 2017b), indicating dose-dependent or ROS-specific responses. For this reason, we monitored total ROS formation in the roots (which are in direct contact with the treatment solution) using fluorescence microscopy and data confirmed the highest signal just in Pb treatment (Fig. 1).
Hydrogen sulfide directs metabolic flux towards the lignan biosynthesis in Linum album hairy roots
2019, Plant Physiology and BiochemistryCitation Excerpt :Non-enzymatic antioxidant molecules, such as phenolic compounds, also scavenge ROS and avoid oxidative damage (Zheng and Wang, 2001). The ROS and NO are involved in elicitor-induced primary and secondary metabolite biosynthesis (Zafari et al., 2016, 2017). The NO is a known elicitor of secondary metabolites such as tanshinone (Du et al., 2015), baicalin (Zhang et al., 2014), taxanes (Wang et al., 2006) and artemisinin (Zheng et al., 2008) in plant tissue cultures.
Water stress alleviation by polyamines and phenolic compounds in Scrophularia striata is mediated by NO and H<inf>2</inf>O<inf>2</inf>
2018, Plant Physiology and BiochemistryNitric oxide production shifts metabolic pathways toward lignification to alleviate Pb stress in Prosopis farcta
2017, Environmental and Experimental BotanyCitation Excerpt :These processes ultimately reduce the damage caused by exposure to stress, facilitate the damage repair system and improve innate immunity in plants (Chakraborty et al., 2015). The induction of immunity occurs by the overexpression of defense-related gene products (Pal et al., 2011), along with several other antioxidant enzymes, and by the higher accumulation of total phenolic content (Zafari et al., 2017). NO has emerged as a potent bioactive signal molecule that triggers a transient metabolic reprogramming in short time of stress exposure (León et al., 2016).