Enhanced Photosynthesis and Carbon Metabolism Favor Arsenic Tolerance in Artemisia annua, a Medicinal Plant as Revealed by Homology-Based Proteomics

Arsenic-Induced Oxidative Stress and Antioxidant Defense in Plants

The non-essential metalloid arsenic (As) is widely distributed in soil and underground water of many countries. Arsenic contamination is a concern because it creates threat to food security in terms of crop productivity and food safety. Plants exposed to As show morpho-physiological, growth and developmental disorder which altogether result in loss of productivity. At physiological level, As-induced altered biochemistry in chloroplast, mitochondria, peroxisome, endoplasmic reticulum, cell wall, plasma membrane causes reactive oxygen species (ROS) overgeneration which damage cell through disintegrating the structure of lipids, proteins, and DNA. Therefore, plants tolerance to ROS-induced oxidative stress is a vital strategy for enhancing As tolerance in plants. Plants having enhanced antioxidant defense system show greater tolerance to As toxicity. Depending upon plant diversity (As hyperaccumulator/non-hyperaccumulator or As tolerant/susceptible) the mechanisms of As accumulation, absorption or toxicity response may differ. There can be various crop management practices such as exogenous application of nutrients, hormones, antioxidants, osmolytes, signaling molecules, different chelating agents, microbial inoculants, organic amendments etc. can be effective against As toxicity in plants. There is information gap in understanding the mechanism of As-induced response (damage or tolerance response) in plants. This review presents the mechanism of As uptake and accumulation in plants, physiological responses under As stress, As-induced ROS generation and antioxidant defense system response, various approaches for enhancing As tolerance in plants from the available literatures which will make understanding the to date knowledge, knowledge gap and future guideline to be worked out for the development of As tolerant plant cultivars.

Carrageenan oligomers and salicylic acid act in tandem to escalate artemisinin production by suppressing arsenic uptake and oxidative stress in Artemisia annua (sweet wormwood) cultivated in high arsenic soil

The present study is aimed to elucidate the effects of concomitant application of irradiated carrageenan (IC) oligomers and salicylic acid (SA) on Artemisia annua L. varieties, viz. "CIM-Arogya" (tolerant) and "Jeevan Raksha" (sensitive) exposed to arsenic (As) stress. Artemisia annua has been known for its sesqui-terpene molecule artemisinin, which is useful in curing malaria. The two compounds, IC and SA, have been established as effective plant growth-promoting molecules for several agricultural and horticultural crops. To test the stress tolerance providing efficacy of IC and SA, the characterization of various physiological and biochemical parameters, growth as well as yield attributes was done in the present experiment. A. annua plants were given various treatments viz. (i) Control (0) (ii) 45 mg As kg^-1 of soil (iii) 80 mg L^-1 IC+45 mg As kg^-1 of soil (iv) 10^-6 M SA+45 mg As kg^-1 of soil (vi) 45 mg As kg^-1 soil+80 mg L^-1 IC+10^-6 M SA. Plants of A. annua suffered from prominent injuries due to oxidative stress generated by As. At 90 and 120 days after planting (DAP), As toxicity was manifested in reduction of most of the studied growth parameters. However, antioxidant activities such as catalase (CAT), peroxidase (POX), superoxide dismutase (SOD), and ascorbate peroxidase (APX) were enhanced in As-stressed conditions and their activities were further enhanced in IC+SA-treated plants. Application of As significantly produced the highest artemisinin content and yield in "CIM-Arogya" over "Jeevan Raksha." Noticeably, the selected plant growth regulators (PGRs) (IC and SA) applied individually through foliage were found efficient, though, the concomitant effect of PGRs was much pronounced compared to their alone application in countering the toxicity of As. The interactive action of PGRs escalated the overall production (yield) of artemisinin (58.7% and 53.8%) in tolerant and sensitive varieties of A. annua in the presence of soil As. Conclusively, the concomitant application of IC and SA proved much effective and successful over their individual use in exploring the overall development of A. annua subjected to As stress.

Heterologous expression of cyanobacterial PCS confers augmented arsenic and cadmium stress tolerance and higher artemisinin in Artemisia annua hairy roots

The present study provides the first report of heterologous expression of phytochelatin synthase from Anabaena PCC 7120 (anaPCS) into the hairy roots of Artemisia annua. Transformed hairy roots of A. annua expressing anaPCS gene showed better tolerance to heavy metals, viz., arsenic (As) and cadmium (Cd) owing to 143 and 191% more As- and Cd-accumulation, respectively, as compared to normal roots with a bioconcentration factor (BCF) of 9.7 and 21.1 for As and Cd, respectively. Under As and Cd stresses, transformed hairy roots possessed significantly higher amounts of phytochelatins and thiols probably due to the presence of both AaPCS (Artemisia annua PCS) and anaPCS. In addition, artemisinin synthesis was also induced in transformed hairy roots under heavy metals stresses. In-silico analysis revealed the presence of conserved motifs in both AaPCS and anaPCS sequences as well as structural modelling of PCS functional domain was conducted. Interaction of AaPCS and anaPCS proteins with CdCl₂ and sodium arsenate gene ontology analysis gave insights to anaPCS functioning in transformed hairy roots of A. annua. The study provides transformed hairy roots of A. annua as an efficient tool for effective phytoremediation with added advantages of artemisinin extraction from hairy roots used for phytoremediation.

SUPPLEMENTARY INFORMATION

The online version contains supplementary material available at 10.1007/s11816-021-00682-5.

Arbuscular Mycorrhiza Improves Photosynthesis and Restores Alteration in Sugar Metabolism in Triticum aestivum L. Grown in Arsenic Contaminated Soil

Contamination of agricultural soil by arsenic (As) is a serious menace to environmental safety and global food security. Symbiotic plant-microbe interaction, such as arbuscular mycorrhiza (AM), is a promising approach to minimize hazards of As contamination in agricultural soil. Even though the potential of AM fungi (AMF) in redeeming As tolerance and improving growth is well recognized, the detailed metabolic and physiological mechanisms behind such beneficial effects are far from being completely unraveled. The present study investigated the ability of an AM fungus, Rhizophagus intraradices, in mitigating As-mediated negative effects on photosynthesis and sugar metabolism in wheat (Triticum aestivum) subjected to three levels of As, viz., 0, 25, and 50 mg As kg-1 of soil, supplied as sodium arsenate. As exposure caused significant decrease in photosynthetic pigments, Hill reaction activity, and gas exchange parameters such as net photosynthetic rate, stomatal conductance, transpiration rate, and intercellular CO2 concentration. In addition, As exposure also altered the activities of starch-hydrolyzing, sucrose-synthesizing, and sucrose-degrading enzymes in leaves. Colonization by R. intraradices not only promoted plant growth but also restored As-mediated impairments in plant physiology. The symbiosis augmented the concentration of photosynthetic pigments, enhanced Hill reaction activity, and improved leaf gas exchange parameters and water use efficiency of T. aestivum even at high dose of 50 mg As kg-1 of soil. Furthermore, inoculation with R. intraradices also restored As-mediated alteration in sugar metabolism by modulating the activities of starch phosphorylase, α-amylase, β-amylase, acid invertase, sucrose synthase, and sucrose-phosphate synthase in leaves. This ensured improved sugar and starch levels in mycorrhizal plants. Overall, the study advocates the potential of R. intraradices in bio-amelioration of As-induced physiological disturbances in wheat plant.

Oligomers of carrageenan regulate functional activities and artemisinin production in Artemisia annua L. exposed to arsenic stress

Recently, a promising technique has come forward in field of radiation-agriculture in which the natural polysaccharides are modified into useful oligomers after depolymerization. Ionizing radiation technology is a simple, pioneering, eco-friendly, and single step degradation process which is used in exploiting the efficiency of the natural polysaccharides as plant growth promoters. Arsenic (As) is a noxious and toxic to growth and development of medicinal plants. Artemisinin is obtained from the leaves of Artemisia annua L., which is effective in the treatment of malaria. The present study was undertaken to find out possible role of oligomers of irradiated carrageenan (IC) on two varieties viz. 'CIM-Arogya' (As-tolerant) and 'Jeevan Raksha' (As-sensitive) of A. annua exposed to As. The treatments applied were 0 (control), 40 IC (40 mg L^-1 IC), 80 IC (80 mg L^-1 IC), 45 As (45 mg kg^-1 soil As), 40 IC + 45 As (40 mg L^-1 IC + 45 mg kg^-1 soil As), and 80 IC + 45 As (80 mg L^-1 IC + 45 mg kg^-1 soil As). The present study was based on various parameters namely plant fresh weight (FW), dry weight (DW), leaf area index (LAI), leaf yield (LY), chlorophyll and carotenoid content, net photosynthetic rate (P_N), stomatal conductance (G_s), carbonic anhydrase activity (CA), proline content (PRO), lipid peroxidation (TBARS), endogenous ROS production (H₂O₂ content), catalase activity (CAT), peroxidase activity (POX), superoxide dismutase activity (SOD), ascorbate peroxidase activity (APX), As content, and artemisinin content in leaves. Plant growth and other physiological and biochemical parameters including enzymatic activities, photosynthetic activity, and its related pigments were negatively affected under As stress. Leaf-applied IC overcame oxidative stress generated due to As in plants by activating antioxidant machinery. Interestingly, leaf-applied IC enhanced the production (content and yield) of artemisinin under high As stress regardless of varieties. The oligomers of IC and As were found to be responsible for the production of endogenous H₂O₂ which has a pivotal role in the biosynthesis of artemisinin in A. annua.

Targeting Acr3 from Ensifer medicae to the plasma membrane or to the tonoplast of tobacco hairy roots allows arsenic extrusion or improved accumulation. Effect of acr3 expression on the root transcriptome

Transgenic tobacco hairy roots expressing the bacterial arsenite efflux pump Acr3 from Ensifer medicae were generated. The gene product was targeted either to the plasma membrane (ACR3 lines) or to the tonoplast by fusing the ACR3 protein to the tonoplast integral protein TIP1.1 (TIP-ACR3 lines). Roots expressing Acr3 at the tonoplast showed greater biomass than those expressing Acr3 at the plasma membrane. Furthermore, higher contents of malondialdehyde (MDA) and RNA degradation in ACR3 lines were indicative of higher oxidative stress. The determination of ROS-scavenging enzymes depicted the transient role of peroxidases in ROS detoxification, followed by the action of superoxide dismutase during both short- and medium-term exposure periods. Regarding As accumulation, ACR3 lines accumulated up to 20-30% less As, whereas TIP-ACR3 achieved a 2-fold increase in As accumulation in comparison to control hairy roots. Strategies that presumably induce As uptake, such as phosphate deprivation or dehydration followed by rehydration in the presence of As, fostered As accumulation up to 10 800 μg g-1. Finally, the effects of the heterologous expression of acr3 on the root transcriptome were assessed. Expression at the plasma membrane induced drastic changes in gene expression, with outstanding overexpression of genes related to electron transport, ATP synthesis and ATPases, suggesting that As efflux is the main detoxification mechanism in these lines. In addition, genes encoding heat shock proteins and those related to proline synthesis and drought tolerance were activated. On the other hand, TIP-ACR3 lines showed a similar gene expression profile to that of control roots, with overexpression of the glutathione and phytochelatin synthesis pathways, together with secondary metabolism pathways as the most important resistance mechanisms in TIP-ACR3, for which As allocation into the vacuole allowed better growth and stress management. Our results suggest that modulation of As accumulation can be achieved by subcellular targeting of Acr3: expression at the tonoplast enhances As accumulation in roots, whereas expression at the plasma membrane could promote As efflux. Thus, both approaches open the possibilities for developing safer crops when grown on As-polluted paddy soils, but expression at the tonoplast leads to better growth and less stressed roots, since the high energy cost of As efflux likely compromises growth in ACR3 lines.

Strong antioxidant capacity of horseradish hairy root cultures under arsenic stress indicates the possible use of Armoracia rusticana plants for phytoremediation

The potential contamination of the food chain is the most important aspect of arsenic (As) pollution, since it is highly toxic to all organisms. Thus, the search for As hyperaccumulators suitable to remove As from contaminated soils appears to be a vital task. Horseradish (Armoracia rusticana), a crop plant with a high potential to accumulate heavy metals, can also serve to study the physiological processes that accompany arsenic stress. The significant adverse effect caused by arsenic exposure is an oxidative stress. Plants have developed a highly organized system to quench free radicals, which includes the action of both enzymatic and non-enzymatic quenching. Saccharides are proposed to possess outstanding antioxidant activity in vitro, and thus, they are likely to effectively quench free radicals also in plant tissues. In this study, root cultures (hairy root type) of horseradish were grown in vitro on media with different concentrations of arsenic (5-60 µg l^-1). Arsenic slowed down the growth, nevertheless up to three-fold biomass increase was achieved at the highest dose. Moreover, root tissues were able to remove as much as 75% of arsenic from the cultivation medium within 7 days. We also evaluated diverse oxidative-stress-related features: contents of reactive oxygen species, the activities of key antioxidant enzymes, and the contents of important antioxidant molecules, such as glutathione, proline, phenolic compounds and non-structural carbohydrates. At all arsenic treatments, we observed a significant proline content increase and enhanced antioxidant enzymes (peroxidase, catalase and glutathione-S-transpherase) activities peaking, however, at different doses. Soluble carbohydrates contents also significantly increased after 7-day treatment a then decreased nearly to the original levels. This study points to efficient antioxidant system of horseradish hairy roots enabling good growth and substantial As accumulation even under high As exposure. Providing that horseradish shares these important features with this model system, we could propose that horseradish is a promising candidate to exploit in arsenic phytoremediation.

Deciphering the non-coding RNA-level response to arsenic stress in rice (Oryza sativa)

Arsenic (As) contamination in subsoil and groundwater is a big problem, especially in many South-East Asian countries. As a staple crop growing under flooded condition in these areas, rice (Oryza sativa L.) becomes a big threat to human health through the food chain since As is highly accumulated in grains. Thus, reducing As accumulation in rice through molecular breeding and identification of rice varieties with low As content are the pressing issues. However, the current understanding on the molecular mechanism of As stress response is still limited for rice. In this study, we performed a comprehensive search for the As-responsive small RNAs (sRNAs) of rice. Briefly, 4,762 and 18,152 sRNAs were identified to be highly activated under As stress in roots and shoots respectively, while 14,603 and 8,308 sRNAs were intensively repressed by As treatment in roots and shoots, respectively. A number of the As-responsive sRNAs found their loci on tRNAs, rRNAs or long non-coding RNAs (lncRNAs). Interestingly, these loci preferentially distributed on the 5' halves of the tRNA, rRNA or lncRNA precursors. Among the above-identified As-responsive sRNAs, 252 Argonaute 1 (AGO1)-enriched sRNAs were extracted for target identification, resulting in 200 pairs of sRNA-protein-coding target interactions. Many targets are functionally involved in the development, stress response, reproduction, or lipid metabolism. Additionally, 56 lncRNAs were discovered to be targeted by nine AGO1-enriched sRNAs, indicating the potential involvement of these lncRNAs in As signaling. Taken together, our results could expand the understanding on the non-coding RNA-mediated As stress response in rice.

Expression of OsTPX Gene Improves Cellular Redox Homeostasis and Photosynthesis Efficiency in Synechococcus elongatus PCC 7942

Cyanobacterial 2-Cys peroxiredoxin (thioredoxin peroxidase, TPX) comprises a family of thiol antioxidant enzymes critically involved in cell survival under oxidative stress. In our previous study, a putative TPX was identified using a proteomics analysis of rice (Oryza sativa L. japonica, OsTPX) seedlings exposed to oxidative stress. This OsTPX gene is structurally similar to the Synechococcus elongatus TPX gene in the highly conserved redox-active disulfide bridge (Cys114, Cys236) and other highly conserved regions. In the present study, the OsTPX gene was cloned into rice plants and S. elongatus PCC 7942 strain to study hydrogen peroxide (H₂O₂) stress responses. The OsTPX gene expression was confirmed using semi-quantitative RT-PCR and western blot analysis. The OsTPX gene expression increased growth under oxidative stress by decreasing reactive oxygen species and malondialdehyde level. Additionally, the OsTPX gene expression in S. elongatus PCC 7942 (OT) strain exhibited a reduced loss of chlorophyll and enhanced photosynthesis efficiency under H₂O₂ stress, thereby increasing biomass yields twofold compared with that of the control wild type (WT) strain. Furthermore, redox balance, ion homeostasis, molecular chaperone, and photosynthetic systems showed upregulation of some genes in the OT strain than in the WT strain by RNA-Seq analysis. Thus, OsTPX gene expression enhances oxidative stress tolerance by increasing cell defense regulatory networks through the cellular redox homeostasis in the rice plants and S. elongatus PCC 7942.

Enhanced arsenic tolerance and secondary metabolism by modulation of gene expression and proteome profile in Artemisia annua L. after application of exogenous salicylic acid

This study was designed to investigate the effect of exogenous application of salicylic acid (SA) on proteins pattern and secondary metabolites in arsenic (As) stressed Artemisia annua. A. annua was treated by As 100 μM, SA 100 μM and combined treatment of SA 100 μM + As 100 μM upto 3 days. Significant accumulation of As was observed in roots than shoots at As 100 μM treatment. Under As treatment, oxidative stress was induced as indicated by increased TBARS content. Biomass, carotenoid, flavonoids were enhanced whereas total chlorophyll pigment was reduced under As treatment. Combined treatment of SA 100 μM + As 100 μM was more effective for increment of biomass, total chlorophyll content, and flavonoids as compared to As 100 μM treatment. Protein profiling revealed 20 differentially abundant proteins by 2-DE PAGE and MALDI-TOF-MS analysis. Identified proteins were related to photosynthesis, energy metabolism, transcriptional regulators, secondary metabolism, lipid metabolism, transport proteins and unknown/hypothetical proteins. All identified proteins were significantly increased in abundance under combined treatments of SA 100 μM + As 100 μM. The expression analysis of key genes involved in biosynthesis of lipid metabolism, signal molecule, transcriptional regulators, artemisinin biosynthetic genes, isoprenoids pathway, terpenes and flavonoids pathway were significantly upregulated under combined treatments of SA 100 μM + As 100 μM, suggesting a fine linkage in regulation of primary and secondary metabolism to modulate tolerance capacity and to improve phytoremediation property of A. annua against arsenic toxicity.

A Proteomic Analysis Provides Novel Insights into the Stress Responses of Caenorhabditis elegans towards Nematicidal Cry6A Toxin from Bacillus thuringiensis

Cry6A represents a novel family of nematicidal crystal proteins from Bacillus thuringiensis. It has distinctive architecture as well as mechanism of action from Cry5B, a highly focused family of nematicidal crystal proteins, and even from other insecticidal crystal proteins containing the conserved three-domain. However, how nematode defends against Cry6A toxin remains obscure. In this study, the global defense pattern of Caenorhabditis elegans against Cry6Aa2 toxin was investigated by proteomic analysis. In response to Cry6Aa2, 12 proteins with significantly altered abundances were observed from worms, participating in innate immune defense, insulin-like receptor (ILR) signaling pathway, energy metabolism, and muscle assembly. The differentially expressed proteins (DEPs) functioning in diverse biological processes suggest that a variety of defense responses participate in the stress responses of C. elegans to Cry6Aa2. The functional verifications of DEPs suggest that ILR signaling pathway, DIM-1, galectin LEC-6 all are the factors of defense responses to Cry6Aa2. Moreover, Cry6Aa2 also involves in accelerating the metabolic energy production which fulfills the energy demand for the immune responses. In brief, our findings illustrate the global pattern of defense responses of nematode against Cry6A for the first time, and provide a novel insight into the mechanism through which worms respond to Cry6A.

Role of fusaric acid in the development of 'Fusarium wilt' symptoms in tomato: Physiological, biochemical and proteomic perspectives

Fusarium wilt is one of the most prevalent and damaging diseases of tomato. Among various toxins secreted by the Fusarium oxysporum f. sp. lycopersici (causal agent of Fusarium wilt of tomato), fusaric acid (FA) is suspected to be a potent pathogenicity factor in tomato wilt disease development. With this rationale the present study was carried out with physiological, biochemical and proteomic perspectives. Treatment of FA was given to the leaves of tomato directly through infiltration to show the characteristic features of Fusarium wilt of tomato. The phytotoxic effect of FA was assessed in the form of cell death in tomato leaves which was observed by increased uptake of Evans blue stain. The measurement of electrolyte leakage was used as an indicator of the extent of cell death. The influence of FA on the leaf photosynthesis of tomato plant was investigated and it was found that FA strongly reduced the photosynthetic pigment contents of tomato leaves resulting to heavy suppression of leaf photosynthesis processes, which therefore affected leaf physiology finally leading to leaf wilting and necrosis. This cell death inducer (FA) produced an enormous oxidative burst during which large quantities of reactive oxygen species (ROS) like H₂O₂ was generated in the treated leaf tissues of tomato plants which was evident from enhancement in lipid peroxidation. To assess the involvement of proteolysis in the cell death cascade induced by FA treatment, total protease activity was measured in the leaf tissues and it was found that the total protease activity increased with the treatment and leading to cell death. Furthermore, proteomic study was used as a powerful tool to understand the alterations in cellular protein expression in response to FA exposure. Differential expression in several proteins was observed in the present study. Proteomic analyses, thus, clearly indicate that proteins belonging to different functional classes are significantly affected in the plant leaf tissues after FA exposure leading to deterioration of structure and metabolism of cells. Thus, it is concluded that FA plays an important role in fungal pathogenicity by decreasing cell viability.

Toxicity of heavy metals and metal-containing nanoparticles on plants

Plants are under the continual threat of changing climatic conditions that are associated with various types of abiotic stresses. In particular, heavy metal contamination is a major environmental concern that restricts plant growth. Plants absorb heavy metals along with essential elements from the soil and have evolved different strategies to cope with the accumulation of heavy metals. The use of proteomic techniques is an effective approach to investigate and identify the biological mechanisms and pathways affected by heavy metals and metal-containing nanoparticles. The present review focuses on recent advances and summarizes the results from proteomic studies aimed at understanding the response mechanisms of plants under heavy metal and metal-containing nanoparticle stress. Transport of heavy metal ions is regulated through the cell wall and plasma membrane and then sequestered in the vacuole. In addition, the role of different metal chelators involved in the detoxification and sequestration of heavy metals is critically reviewed, and changes in protein profiles of plants exposed to metal-containing nanoparticles are discussed in detail. Finally, strategies for gaining new insights into plant tolerance mechanisms to heavy metal and metal-containing nanoparticle stress are presented. This article is part of a Special Issue entitled: Plant Proteomics--a bridge between fundamental processes and crop production, edited by Dr. Hans-Peter Mock.

Birth of plant proteomics in India: a new horizon

In the post-genomic era, proteomics is acknowledged as the next frontier for biological research. Although India has a long and distinguished tradition in protein research, the initiation of proteomics studies was a new horizon. Protein research witnessed enormous progress in protein separation, high-resolution refinements, biochemical identification of the proteins, protein-protein interaction, and structure-function analysis. Plant proteomics research, in India, began its journey on investigation of the proteome profiling, complexity analysis, protein trafficking, and biochemical modeling. The research article by Bhushan et al. in 2006 marked the birth of the plant proteomics research in India. Since then plant proteomics studies expanded progressively and are now being carried out in various institutions spread across the country. The compilation presented here seeks to trace the history of development in the area during the past decade based on publications till date. In this review, we emphasize on outcomes of the field providing prospects on proteomic pathway analyses. Finally, we discuss the connotation of strategies and the potential that would provide the framework of plant proteome research.

BIOLOGICAL SIGNIFICANCE

The past decades have seen rapidly growing number of sequenced plant genomes and associated genomic resources. To keep pace with this increasing body of data, India is in the provisional phase of proteomics research to develop a comparative hub for plant proteomes and protein families, but it requires a strong impetus from intellectuals, entrepreneurs, and government agencies. Here, we aim to provide an overview of past, present and future of Indian plant proteomics, which would serve as an evaluation platform for those seeking to incorporate proteomics into their research programs. This article is part of a Special Issue entitled: Proteomics in India.

The Energy Metabolism in Caenorhabditis elegans under The Extremely Low-Frequency Electromagnetic Field Exposure

A literal mountain of documentation generated in the past five decades showing unmistakable health hazards associated with extremely low-frequency electromagnetic fields (ELF-EMFs) exposure. However, the relation between energy mechanism and ELF-EMF exposure is poorly understood. In this study, Caenorhabditis elegans was exposed to 50 Hz ELF-EMF at intensities of 0.5, 1, 2, and 3 mT, respectively. Their metabolite variations were analyzed by GC-TOF/MS-based metabolomics. Although minimal metabolic variations and no regular pattern were observed, the contents of energy metabolism-related metabolites such as pyruvic acid, fumaric acid, and L-malic acid were elevated in all the treatments. The expressions of nineteen related genes that encode glycolytic enzymes were analyzed by using quantitative real-time PCR. Only genes encoding GAPDH were significantly upregulated (P < 0.01), and this result was further confirmed by western blot analysis. The enzyme activity of GAPDH was increased (P < 0.01), whereas the total intracellular ATP level was decreased. While no significant difference in lifespan, hatching rate and reproduction, worms exposed to ELF-EMF exhibited less food consumption compared with that of the control (P < 0.01). In conclusion, C. elegans exposed to ELF-EMF have enhanced energy metabolism and restricted dietary, which might contribute to the resistance against exogenous ELF-EMF stress.