Stress Adaptation Mechanisms Research Articles

Kinetin modulates physiological and biochemical attributes of Vigna radiata L. seedlings exposed to 2-benzoxazolinone stress

Cytokinins are growth regulators concerned with influencing numerous plant metabolic and stress adaptive mechanisms under adversity. The present investigation was conducted to study the role of kinetin (KN) in ameliorating the damaging effects of allelochemical 2-benzoxazolinone (BOA) on Vigna radiata seedlings. The experiment was undertaken in sand culture under glasshouse conditions where plants were exposed to BOA (1 and 1.5 mM) by root and KN (1 mM) foliarly and then sampled for different growth parameters. BOA at both concentrations induced growth retardation which was more pronounced at the higher dose (1.5 mM). BOA toxicity gradually decreased photosynthetic pigment, relative water, protein, anthocyanin content, nitrate reductase activity and antioxidant enzyme activity. On contrary, enhanced electrolyte leakage (EL), lipid peroxidation (LP), hydrogen peroxide (H2O2), proline content and phenylalanine ammonia lyase activity (PAL). The foliar KN supplementation assisted in growth restoration by influencing several physiobiochemical attributes. KN-induced growth amelioration was reflected as reduced generation of reactive oxygen species and membrane stability with reduced LP and EL. The seedlings exposed to combined BOA and KN treatment exhibited higher antioxidant enzyme activity and total phenolic content (TPC) coupled with proline accumulation which play significant role in combating stress efficiently. The results revealed that KN has potential to buttress the defence system of crops grown in soil having higher BOA content. In future, research emphasis should be given on gene regulation mechanisms by allelopathins in plant system.

Less Can Be More: The Hormesis Theory of Stress Adaptation in the Global Biosphere and Its Implications.

A dose-response relationship to stressors, according to the hormesis theory, is characterized by low-dose stimulation and high-dose inhibition. It is non-linear with a low-dose optimum. Stress responses by cells lead to adapted vitality and fitness. Physical stress can be exerted through heat, radiation, or physical exercise. Chemical stressors include reactive species from oxygen (ROS), nitrogen (RNS), and carbon (RCS), carcinogens, elements, such as lithium (Li) and silicon (Si), and metals, such as silver (Ag), cadmium (Cd), and lead (Pb). Anthropogenic chemicals are agrochemicals (phytotoxins, herbicides), industrial chemicals, and pharmaceuticals. Biochemical stress can be exerted through toxins, medical drugs (e.g., cytostatics, psychopharmaceuticals, non-steroidal inhibitors of inflammation), and through fasting (dietary restriction). Key-lock interactions between enzymes and substrates, antigens and antibodies, antigen-presenting cells, and cognate T cells are the basics of biology, biochemistry, and immunology. Their rules do not obey linear dose-response relationships. The review provides examples of biologic stressors: oncolytic viruses (e.g., immuno-virotherapy of cancer) and hormones (e.g., melatonin, stress hormones). Molecular mechanisms of cellular stress adaptation involve the protein quality control system (PQS) and homeostasis of proteasome, endoplasmic reticulum, and mitochondria. Important components are transcription factors (e.g., Nrf2), micro-RNAs, heat shock proteins, ionic calcium, and enzymes (e.g., glutathion redox enzymes, DNA methyltransferases, and DNA repair enzymes). Cellular growth control, intercellular communication, and resistance to stress from microbial infections involve growth factors, cytokines, chemokines, interferons, and their respective receptors. The effects of hormesis during evolution are multifarious: cell protection and survival, evolutionary flexibility, and epigenetic memory. According to the hormesis theory, this is true for the entire biosphere, e.g., archaia, bacteria, fungi, plants, and the animal kingdoms.

Exogenous Melatonin Enhances Cd Tolerance and Phytoremediation Efficiency by Ameliorating Cd-Induced Stress in Oilseed Crops: A Review

Heavy metal pollution is of increasing global concern as it adversely impacts different spheres including pedosphere, hydrosphere, biosphere, and humansphere. Cadmium (Cd) contamination of agriculture soil has become a thoughtful challenge across the globe due to uncontrolled anthropogenic activities, limiting agricultural productivity and disturbing eco-environment sustainability. Sustainable mitigation strategies are, therefore, required for effective Cd decontamination. Biostimulation is a promising method to improve and stimulate life processes of plants in general and oilseed crops in particular, without posing threats to eco-environment sustainability and safer food production. Melatonin (N-acetyl-5-methoxytryptamine), a recognized pleiotropic molecule, has emerged as a research highlight regarding its role as an effective natural plant growth promoter, a broad spectrum antioxidant, and more specifically an efficient biostimulator to improve Cd-induced tolerance of plants for phytoremediation purposes and simultaneous biofuel production. This review provides a novel insight to understand the multifunctional role of melatonin in improving Cd phytoremediation capacity together with reducing phytotoxicity in oilseed crops, which was not previously assessed. Among oilseed crops, Brassicaceae spp. have unique stress adaptive mechanisms with exceptionally high Cd accumulating capabilities, apart from the diverse agri-horticultural importance. Interestingly, the discovery of dynamic approaches regarding melatonin application helped to better understand the basic mechanisms involved in melatonin-mediated responses against Cd stress in oilseed crops. Our review will provide a useful basis for the development of alternative strategies to genetically engineer low-Cd-content oilseed crops, with the aim of improving eco-friendly crop production and ensuring food safety. Furthermore, future researches will be supposed to provide more genetic evidences about Cd-induced melatonin regulation in higher plants.

The biotechnological importance of the plant-specific NAC transcription factor family in crop improvement

Climate change, malnutrition, and food insecurity are the inevitable challenges being faced by the agriculture sector today. Plants are susceptible to extreme temperatures during the crucial phases of flowering and seed development, and elevated carbon levels also lead to yield losses. Productivity is also affected by floods and droughts. Therefore, increasing plant yield and stress tolerance are the priorities to be met through novel biotechnological interventions. The contributions of NAC genes towards enhancing plant survivability under stress is well known. Here we focus on the potential of NAC genes in the regulation of abiotic stress tolerance, secondary cell wall synthesis, lateral root development, yield potential, seed size and biomass, ROS signaling, leaf senescence, and programmed cell death. Once naturally tolerant candidate NAC genes have been identified, and the nature of their association with growth and fitness against multi-environmental stresses has been determined, they can be exploited for building inherent tolerance in future crops via transgenic technologies. An update on the latest developments is provided in this review, which summarizes the current understanding of the roles of NAC in the establishment of various stress-adaptive mechanisms in model and food crop plants.

Characterizing the Leaf Transcriptome of Chrysanthemum rhombifolium (Ling et C. Shih), a Drought Resistant, Endemic Plant From China.

Chrysanthemum rhombifolium (Ling et C. Shih), an endemic plant that is extremely well-adapted to harsh environments. However, little is known about its molecular biology of the plant's resistant traits against stress, or even its molecular biology of overall plant. To investigate the molecular biology of C. rhombifolium and mechanism of stress adaptation, we performed transcriptome sequencing of its leaves using an Illumina platform. A total of 130,891 unigenes were obtained, and 97,496 (~74.5%) unigenes were annotated in the public protein database. The similarity search indicated that 40,878 and 74,084 unigenes showed significant similarities to known proteins from NCBI non-redundant and Swissprot protein databases, respectively. Of these, 56,213 and 42,005 unigenes were assigned to the Gene Ontology (GO) database and Cluster of Orthologous Groups (COG), respectively, and 38,918 unigenes were mapped into five main categories, including 18 KEGG pathways. Metabolism was the largest category (23,128, 59.4%) among the main KEGG categories, suggesting active metabolic processes in C. rhombifolium. About 2,459 unigenes were annotated to have a role in defense mechanism or stress tolerance. Transcriptome analysis of C. rhombifolium revealed the presence of 12,925 microsatellites in 10,524 unigenes and mono, trip, and dinucleotides having higher polymorphism rates. The phylogenetic analysis based on GME gene among related species confirmed the reliability of the transcriptomic data. This work is the first genetic study of C. rhombifolium as a new plant resource of stress-tolerant genes. This large number of transcriptome sequences enabled us to comprehensively understand the basic genetics of C. rhombifolium and discover novel genes that will be helpful in the molecular improvement of chrysanthemums.

Insights in the molecular mechanisms of an azole stress adapted laboratory-generated Aspergillus fumigatus strain.

A pan-azole-resistant strain was generated in vitro, in which drug transporter overexpression was a major trait. Analyses suggested a role of the transporter inhibitor milbemycin oxime in inhibiting drug transporters and potentiating azole activity.

Review on Stress Tolerance in Campylobacter jejuni.

Campylobacter spp. are the leading global cause of bacterial colon infections in humans. Enteropathogens are subjected to several stress conditions in the host colon, food complexes, and the environment. Species of the genus Campylobacter, in collective interactions with certain enteropathogens, can manage and survive such stress conditions. The stress-adaptation mechanisms of Campylobacter spp. diverge from other enteropathogenic bacteria, such as Escherichia coli, Salmonella enterica serovar Typhi, S. enterica ser. Paratyphi, S. enterica ser. Typhimurium, and species of the genera Klebsiella and Shigella. This review summarizes the different mechanisms of various stress-adaptive factors on the basis of species diversity in Campylobacter, including their response to various stress conditions that enhance their ability to survive on different types of food and in adverse environmental conditions. Understanding how these stress adaptation mechanisms in Campylobacter, and other enteric bacteria, are used to overcome various challenging environments facilitates the fight against resistance mechanisms in Campylobacter spp., and aids the development of novel therapeutics to control Campylobacter in both veterinary and human populations.

Understanding heat and drought stress adaptation mechanisms in maize on the molecular level

Despite the importance of maize as a staple crop in Southern Africa, production remains subdued, averaging 1 tha−1 under smallholder farming systems. Although the low yields can be attributed to several biotic (e.g., pests and diseases) and abiotic (e.g., infertile soils) phenomenon, the climate change-induced abiotic stresses (in particular, heat and drought) are regarded as the major constrains threatening maize productivity, globally. Since climatic models are predicting exacerbated incidences of drought and heat stress, societies that depend on maize for survival will also be at risk if plant breeders lose focus in developing varieties productive under these predicted climatic scenarios. In this review, we provide: (1) a summary of the known effects of drought and heat stress on maize production, (2) a summation of the morpho-physiological adaptation mechanisms of maize to heat and drought as well as (3) a summary of strides made on the molecular front in understanding how heat and drought stress tolerance/resistance in maize is genetically controlled. We hypothesize that a better understanding of how heat and drought stress impacts of maize productivity, together with a deeper appreciation of mechanisms employed by maize germplasm tolerant/resistant to the stress conditions, can guide maize breeders in structuring a holistic program for developing maize varieties productive under these abiotic stresses.

TMT-Based Quantitative Proteomics Analysis of the Fish-Borne Spoiler Shewanella putrefaciens Subjected to Cold Stress Using LC-MS/MS

Shewanella putrefaciens is a specific spoilage bacterium for fish during cold storage. To better understand the molecular mechanisms of cold stress adaptation of S. putrefaciens, tandem mass tag- (TMT-) based quantitative proteomic analysis was performed to detect the effects of cold stress on protein expression profiles in S. putrefaciens which had been cultivated at 4°C and 30°C, respectively. A total of 266670 peptide spectrum matching numbers were quantified proteins after data analysis. Of the 2292 proteins quantitatively analyzed, a total of 274 were found to be differentially expressed (DE) under cold stress compared with the nonstress control. By integrating the results of Kyoto Encyclopedia of Genes and Genomes (KEGG) analyses, 9 common KEGG terms were found notable for the cold-responsive proteins. Generally, the DE proteins involved in carbohydrate, amino acid, and fatty acid biosynthesis and metabolism were significantly upregulated, leading to a specific energy conservation survival mode. The DE proteins related to DNA repair, transcription, and translation were upregulated, implicating change of gene expression and more protein biosynthesis needed in response to cold stress.

Identification of Salt Stress-Responsive Proteins in Maize (Zea may) Seedlings Using iTRAQ-Based Proteomic Technique.

Background: Soil salinity is a major abiotic stress that limits plant growth and yield worldwide. Objective: To better understand the mechanism of salt stress adaptation in maize (Zea may), proteomic analysis of maize responses to salt stress were analyzed in seedling.Materials and Methods: Taking maize seedlings untreated and treated with NaCl for 24 h as material, isobaric tags for relative and absolute quantitation (iTRAQ) were used to analyze the protein expression profile of maize seedlings after salt stress.Results: The result showed that 270 differentially expression proteins (DEPs) were identified in maize seedlings after salt stress. The majority proteins had functions related to translation, ribosomal structure and biogenesis (15%), posttranslational modification, protein turnover, chaperones (14%) and others metabolism. Quantitative real-time PCR analysis showed that the EF-Tu, peroxiredoxin, FoF1-type ATP synthase, glutamate dehydrogenase, glyceraldehyde-3-phosphate dehydrogenase, Acetyl-CoA acetyltransferase and nucleoside diphosphate kinase genes were up-regulated in the adaptation of maize to salt stress.Conclusions: The coped with salt stress of maize seedlings might be included nitrogen and glutamate (Glu) metabolism and energy homeostasis, nucleotide transport and metabolism, soluble sugar, fatty acid and nucleoside triphosphates synthesis. Moreover, the enhancement of plant to scavenge ROS, such as peroxiredoxin, might play significant roles in the adaptation of maize to salt stress.Taken together, these proteins might have important roles in defense mechanisms against salt stress in maize.We hope that this study provides valuable information for the further utilization and study on the molecular mechanisms of defense mechanisms in maize.

Systems biology reveals key tissue-specific metabolic and transcriptional signatures involved in the response of Medicago truncatula plant genotypes to salt stress

Salt stress is an important factor limiting plant productivity by affecting plant physiology and metabolism. To explore salt tolerance adaptive mechanisms in the model legume Medicago truncatula, we used three genotypes with differential salt-sensitivity: TN6.18 (highly sensitive), Jemalong A17 (moderately sensitive), and TN1.11 (tolerant). Cellular damage was monitored in roots and leaves 48 h after 200 mM NaCl treatment by measuring lipid peroxidation, nitric oxide, and hydrogen peroxide contents, further supported by leaf stomatal conductance and chlorophyll readings. The salt-tolerant genotype TN1.11 displayed the lowest level of oxidative damage, in contrast to the salt sensitive TN6.18, which showed the highest responses. Metabolite profiling was employed to explore the differential genotype-related responses to stress at the molecular level. The metabolic data in the salt tolerant TN1.11 roots revealed an accumulation of metabolites related to the raffinose pathway. To further investigate the sensitivity to salinity, global transcriptomic profiling using microarray analysis was carried out on the salt-stressed sensitive genotypes. In TN6.18, the transcriptomic analysis identified a lower expression of many genes related to stress signalling, not previously linked to salinity, and corresponding to the TIR-NBS-LRR gene class. Overall, this global approach contributes to gaining significant new insights into the complexity of stress adaptive mechanisms and to the identification of potential targets for crop improvement.

VvBAP1, a Grape C2 Domain Protein, Plays a Positive Regulatory Role Under Heat Stress.

Temperature is considered one of the critical factors directly influencing grapevine during the three primary growth and development stages: sprout, flowering, and fruit-coloring, which is strongly correlated to the yield and quality of the grape. The grapevine is frequently exposed to high-temperature conditions that are detrimental to growth. However, the mechanisms of the heat stress response and adaptation in grapevine are not adequately studied. The Arabidopsis copine gene AtBON1 encodes a highly conserved protein containing two C2 domains at the amino terminus, participation in cell death regulation and defense responses. Previously, we showed that a BON1 association protein from the grapevine, VvBAP1, plays a positive role in cold tolerance. Similarly, the involvement of VvBAP1 in the resistance to heat stress was also found in the present study. The results indicated VvBAP1 was significantly induced by high temperature, and the elevated expression of VvBAP1 was significantly higher in the resistant cultivars than the sensitive cultivars under heat stress. Seed germination and phenotypic analysis results indicated that overexpression of VvBAP1 improved Arabidopsis thermoresistance. Compared with the wild type, the chlorophyll content and net photosynthetic rate in VvBAP1 overexpressing Arabidopsis plants were markedly increased under heat stress. At high temperatures, overexpression of VvBAP1 also enhanced antioxidant enzyme activity as well as their corresponding gene transcription levels, to reduce the accumulation of reactive oxygen species and lipid peroxidation. Besides, the transcriptional activities of HSP70, HSP101, HSFA2, and HSFB1 in VvBAP1 overexpressing Arabidopsis plants were significantly up-regulated compare to the wild type. In summary, we propose that VvBAP1 may play a potential important role in enhanced grapevine thermoresistance, primarily through the enhancement of antioxidant enzyme activity and promoted heat stress response genes expression.

Liver and spleen transcriptome reveals that Oreochromis aureus under long-term salinity stress may cause excessive energy consumption and immune response

To investigate the physiological responses of Oreochromis aureus to salinity fluctuations at the molecular level. We used RNA-seq to explore the differentially expressed genes (DEGs) in the liver and spleen of O. aureus at 0, 3, 7 and 11 ppt (parts per thousand) salinity levels. Herein, De novo assembly generated 71,009 O. aureus unigenes, of which 34,607 were successfully mapped to the four major databases. A total of 120 shared DEGs were identified in liver and spleen transcripts, of which 83 were up-regulated and 37 were down-regulated. GO and KEGG analysis found a total of 26 significant pathways, mainly including energy metabolism, immune response, ion transporters and signal transduction. The trend module category of DEGs showed that the genes (e.g., FASN, ODC1, CD22, MRC, TRAV and SLC7 family) involved in the change-stable-change (1) and the constant-change categories (2) were highly sensitive to salinity fluctuations, which were of great value for further study. Based on these results, it would help provide basic data for fish salinity acclimation, and provide new insights into evolutionary response of fish to various aquatic environments in the long-term stress adaptation mechanism.

The impact of food model system structure on the inactivation of Listeria innocua by cold atmospheric plasma and nisin combined treatments

Novel processing methods such as cold atmospheric plasma (CAP) and natural antimicrobials like nisin, are of interest to replace traditional food decontamination approaches as, due to their mild nature, they can maintain desirable food characteristics, i.e., taste, texture, and nutritional content. However, the microbial growth characteristics (planktonic growth/surface colonies) and/or the food structure itself (liquid/solid surface) can impact the inactivation efficacy of these novel processing methods. More specifically, cells grown as colonies on a solid(like) surface experience a completely different growth environment to cells grown planktonically in liquid, and thus could display a different response to novel processing treatments through stress adaptation and/or cross protection mechanisms. The order in which combined treatments are applied could also impact their efficacy, especially if the mechanisms of action are complementary.This work presents a fundamental study on the efficacy of CAP and nisin, alone and combined, as affected by food system structure. More specifically, Listeria innocua was grown planktonically (liquid broth) or on a viscoelastic Xanthan gum gel system (1.5% w/v) and treated with CAP, nisin, or a combination of the two. Both the inactivation system, i.e., liquid versus solid(like) surface and the growth characteristics, i.e., planktonic versus colony growth, were shown to impact the treatment efficacy. The combination of nisin and CAP was more effective than individual treatments, but only when nisin was applied before the CAP treatment.This study provides insight into the environmental stress response/adaptation of L. innocua grown on structured systems in response to natural antimicrobials and novel processing technologies, and is a step towards the faster delivery of these food decontamination methods from the bench to the food industry.

Heat stress alters muscle protein and amino acid metabolism and accelerates liver gluconeogenesis for energy supply in broilers

Heat stress impairs growth performance and alters body protein and amino acid metabolism. This study was investigated to explore how body protein and amino acid metabolism changed under heat stress (HS) and the stress adaptation mechanism. A total of 144 broilers (28 d old) were divided into 3 treatment groups for 1 wk: HS group (32°C), normal control group (22°C), and pair-feeding group (22°C). We found that HS elevated the feed-to-gain ratio, reduced the ADFI and ADG, decreased breast muscle mass and plasma levels of several amino acids (glycine, lysine, threonine, and tyrosine), and increased serum glutamic oxaloacetic transaminase (GOT) activity and corticosterone (CORT) level and liver GOT and glutamic pyruvic transaminase activities. Heat stress elevated muscle atrophy F-box mRNA expression and reduced mRNA expression of the 70-kD ribosomal protein S6 kinase in the breast muscle of broilers. Broilers in the HS group exhibited striking increases of mRNA expressions of solute carrier family 1 member 1, family 3 member 1, family 7 member 1, and family 7 member-like in the liver and liver gluconeogenesis genes (PCKc, PCKm, PC, and FBP1) in comparison with the other 2 groups. In conclusion, HS increased the circulating CORT level and subsequently caused muscle protein breakdown to provide amino acid substrates to liver gluconeogenesis responsible for energy supply.

The Emerging Roles of Diacylglycerol Kinase (DGK) in Plant Stress Tolerance, Growth, and Development

Diacylglycerol kinase (DGK) is recognized as the key enzyme of the lipid signaling pathway, which involves the transduction of messages from hormones, neurotransmitters, and immunologic and growth factors. Regarding their essential role in animal physiology, many plant biologists have predicted a similar enzymatic influence in plants. However, a small number of recent studies have revealed the complexity of the involvement of DGK genes in the modulation of plant growth, development, and adaptation in both biotic and abiotic stress conditions. Here, we describe recent discoveries on the role of DGK genes in the plants’ responses to biotic or abiotic stressors. Moreover, we discuss how DGK enzymes regulate plant cellular activities during the adaptation of plants to a readily changing environment. DGK is an enzyme that plays a pivotal role in plant lipid signaling, by catalyzing the phosphorylation of the diacylglycerol (DAG) to phosphatidic acid (PA), which is a crucial molecule in a plant’s metabolic network, leading to its response to various external stresses. DGK enzymes are the principal moderators of PA generation in plant cells; this consequently affects its derived products—hence, enabling their activities in lipid signaling networks and cell homeostasis. Thus, understanding the DGK operational mode and interactions between the production and accumulation of PA would constitute a significant advancement in investigating the mechanism of stress adaptation in plants.

Signs of a phyllospheric lifestyle in the genome of the stress-tolerant strain Azospirillum brasilense Az19

Azospirillum brasilense Az19 is a plant-beneficial bacterium capable of protecting plants from the negative effects of drought. The objective of this study was to determine and analyze the genomic sequence of strain Az19 as a means of identifying putative stress-adaptation mechanisms. A high-quality draft genome of ca. 7 Mb with a predicted coding potential of 6710 genes was obtained. Phylogenomic analyses confirmed that Az19 belongs to the brasilense clade and is closely related to strains Az39 and REC3. Functional genomics revealed that the denitrification pathway of Az19 is incomplete, which was in agreement with a reduced growth on nitrate under low O2 concentrations. Putative genes of the general stress response and oxidative stress-tolerance, as well as synthesis of exopolysaccharides, carotenoids, polyamines and several osmolytes, were detected. An additional poly-beta-hydroxybutyrate (PHB) synthase coding gene was found in Az19 genome, but the accumulation of PHB did not increase under salinity. The detection of exclusive genes related to DNA repair led to discover that strain Az19 also has improved UV-tolerance, both in vitro and in planta. Finally, the analysis revealed the presence of multiple kaiC-like genes, which could be involved in stress-tolerance and, possibly, light responsiveness. Although A. brasilense has been a model for the study of beneficial plant-associated rhizobacteria, the evidence collected in this current study suggests, for the first time in this bacterial group, an unexpected possibility of adaptation to the phyllosphere.

MRNA profile provides novel insights into stress adaptation in mud crab megalopa, Scylla paramamosain after salinity stress

BackgroundMud crab, Scylla paramamosain, a euryhaline crustacean species, mainly inhabits the Indo-Western Pacific region. Wild mud crab spawn in high-salt condition and the salinity reduced with the growth of the hatching larvae. When the larvae grow up to megalopa, they migrate back to estuaries and coasts in virtue of the flood tide, settle and recruit adult habitats and metamorphose into the crablet stage. Adult crab can even survive in a wide salinity of 0–35 ppt. To investigate the mRNA profile after salinity stress, S. paramamosain megalopa were exposed to different salinity seawater (low, 14 ppt; control, 25 ppt; high, 39 ppt).ResultsFirstly, from the expression profiles of Na+/K+/2Cl- cotransporter, chloride channel protein 2, and ABC transporter, it turned out that the 24 h might be the most influenced duration in the short-term stress. We collected megalopa under different salinity for 24 h and then submitted to mRNA profiling. Totally, 57.87 Gb Clean Data were obtained. The comparative genomic analysis detected 342 differentially expressed genes (DEGs). The most significantly DEGs include gamma-butyrobetaine dioxygenase-like, facilitated trehalose transporter Tret1, sodium/potassium-transporting ATPase subunit alpha, rhodanese 1-like protein, etc. And the significantly enriched pathways were lysine degradation, choline metabolism in cancer, phospholipase D signaling pathway, Fc gamma R-mediated phagocytosis, and sphingolipid signaling pathway. The results indicate that in the short-term salinity stress, the megalopa might regulate some mechanism such as metabolism, immunity responses, osmoregulation to adapt to the alteration of the environment.ConclusionsThis study represents the first genome-wide transcriptome analysis of S. paramamosain megalopa for studying its stress adaption mechanisms under different salinity. The results reveal numbers of genes modified by salinity stress and some important pathways, which will provide valuable resources for discovering the molecular basis of salinity stress adaptation of S. paramamosain larvae and further boost the understanding of the potential molecular mechanisms of salinity stress adaptation for crustacean species.

Expression and evolution of the phospholipase C gene family in Brachypodium distachyon.

Phospholipase C (PLC) is an enzyme that hydrolyzes phospholipids and plays an important role in plant growth and development. The Brachypodium distachyon is a model plant of Gramineae, but the research on PLC gene family of Brachypodium has not been reported. This study was performed to identify the PLC family gene in Brachypodium and to determine the expression profiles of PLCs under the abiotic stress. Complete genome sequences and transcriptomes of Brachypodium were downloaded from the PLAZA. The hidden Markov model-based profile of the conserved PLC domain was submitted as a query to identify all potential PLC domain sequences with HMMER software. Expression profiles of BdPLCs were obtained based on the qRT-PCR analysis. There were 8 PLC genes in Brachypodium (BdPI-PLCs 1-4 and BdNPCs 1-4). All members of BdPI-PLC had three conserved domains of X, Y, and C2, and no EF-hand was found. All BdNPCs contained a phosphatase domain. BdPI-PLC genes were distributed on Chr1, Chr2 and Chr4, with different types and numbers of cis-regulatory elements in their respective gene promoters. Phylogenetic analysis showed that the genetic relationship between Brachypodium and rice was closer than Arabidopsis. The expression patterns of BdPI-PLC gene under abiotic stresses (drought, low temperature, high temperature and salt stress) were up-regulated, indicated their important roles in response to low temperature, high temperature, drought and salt stresses. This study provides comprehensive information for the study of Brachypodium PLC gene family and lays a foundation for further research on the molecular mechanism of Brachypodium stress adaptation.

Abstract B55: MYCN promotes m6a-dependent translation of eEF2K mRNA during adaptation to ER stress

Abstract MYCN-amplified neuroblastoma is one of the most common and malignant pediatric tumors with low survival rates. Attempts to develop specific inhibitors to target MYCN have not been successful, prioritizing research into MYCN downstream targets. It was previously shown that eukaryotic translation elongation factor 2 (eEF2K) is upregulated in MYCN-amplified neuroblastoma and facilitates its adaptation to the nutrient deprivation (ND). However, the mechanism of eEF2K overexpression and its role in such adaptation is unknown. Using SUnSET assays, we showed that MYCN overexpression increases protein synthesis rates, demonstrating that MYCN-amplified cells depend on protein biosynthesis to cover the needs of fast proliferation. Enhanced protein biosynthesis increases the susceptibility for protein aggregates and subsequent unfolded protein response (UPR) activation and ER stress. ER stress also occurs under ND due to accumulation of unglycosylated proteins in the ER. To check how MYCN-amplified tumors might adapt to ER stress, we performed gene set enrichment analyses (GSEA) of genes that are overexpressed in MYCN amplified neuroblastoma and found “UPR” in the top 10 gene sets. As eEF2K regulates protein synthesis rates by slowing down the elongation step of mRNA translation, we examined whether eEF2K is part of the ER stress adaptation mechanism in MYCN-amplified cells. We found that during ND, eEF2K KO cells are more sensitive to thapsigargin (Tg) and tunicamycin (Tm), ER stress-inducing compounds, and show higher levels of ATF4, a major ER stress marker. Notably, low doses of cycloheximide, which blocks translation elongation, rescued the phenotype in eEF2K KO cells, confirming that the observed effect of eEF2K KO is linked to translation elongation. Finally, GSEA of RNAseq data obtained from TET21N WT vs. eEF2K KO after ND showed upregulation of genes responsible for the UPR and ER stress in eEF2K KO cells. Therefore, eEF2K appears to be linked to ER stress adaptation. To find potential mechanisms of MYCN-dependent regulation of eEF2K expression, we performed bioinformatic analyses of the eEF2K mRNA and found potential binding sites for METTL3, an enzyme that functions in the methylation of adenosine residues in mRNAs, in the eEF2K 3´-UTR. METTL3 knockdown resulted in a marked decrease of eEF2K protein without significant changes at the mRNA level. We applied polysome fractionation to study the effect of m6a modification on eEF2K mRNA translation. We discovered that METTL3 KD brings eEF2K mRNA to lighter polysome fractions compared with WT cells. As YTHDF1 is the only known reader of m6a modification that increases translation, we performed YTHDF1 knockdown and observed a decrease in eEF2K protein levels. Our findings indicate that MYCN amplified neuroblastoma cells increase translation of eEF2K mRNAs via a METTL3-YTHDF1 axis, and that this potentially functions as part of an adaptation mechanism under increased protein synthesis and subsequent ER stress. Citation Format: Andrii Vislovukh, Cristopher Hughes, Michael Lizardo, Poul H. Sorensen. MYCN promotes m6a-dependent translation of eEF2K mRNA during adaptation to ER stress [abstract]. In: Proceedings of the AACR Special Conference on the Advances in Pediatric Cancer Research; 2019 Sep 17-20; Montreal, QC, Canada. Philadelphia (PA): AACR; Cancer Res 2020;80(14 Suppl):Abstract nr B55.