Expression Of Stress-responsive Genes Research Articles

Screening of mungbean for drought tolerance and transcriptome profiling between drought-tolerant and susceptible genotype in response to drought stress

Mungbean, is a widely cultivated pulse crop in India, experiences severe drought stress during the cultivation period. The mechanism of drought tolerance in mungbean is not well understood. In this presents study we screened 7 widely cultivated mungbean genotypes towards their drought sensitivity at seedling stage and transcriptome sequencing of drought-tolerant and susceptible genotype to understand the drought tolerance mechanism. Our physiological data such as increase in root length, shoot length, fresh weight, dry weight, relative water content (RWC), proline content, MDA content and molecular data in terms of quantitative expression of drought stress responsive genes under 3-d drought stress in mungbean suggests that, K851 seems to be most drought tolerant and PDM-139 as drought susceptible genotype. The transcriptomic study between K-851 and PDM-139 revealed 22,882 differentially expressed genes (DEGs) which were identified under drought stress, and they were mainly mapped to phytohormone signal transduction, carbon metabolism and flavonoid biosynthesis. Out of these, 10,235 genes were up-regulated and 12,647 genes were down-regulated. Furthermore, we found that, the DEGs related to, phytohormone signal transduction, carbon metabolism and flavonoid biosynthesis and they were more induced in K-851. Our data suggested that, the drought tolerant genotype K-851, scavenges the damage of drought stress by producing more amount of osmolytes, ROS scavengers and sugar biosynthesis.

Drought-hardening improves drought tolerance in Nicotiana tabacum at physiological, biochemical, and molecular levels

BackgroundDrought stress is the most harmful one among other abiotic stresses with negative impacts on crop growth and development. Drought-hardening is a feasible and widely used method in tobacco seedlings cultivation. It has gained extensive interests due to its role in improving drought tolerance. This research aimed to investigate the role of drought-hardening and to unravel the multiple mechanisms underlying tobacco drought tolerance and adaptation.ResultsThis study was designed in which various drought-hardening treatments (CK (no drought-hardening), T1 (drought-hardening for 24 h), T2 (drought-hardening for 48 h), and T3 (drought-hardening for 72 h)) were applied to two tobacco varieties namely HongHuaDaJinYuan (H) and Yun Yan-100 (Y). The findings presented a complete framework of drought-hardening effect at physiological, biochemical, and gene expression levels of the two tobacco varieties under drought stress. The results showed that T2 and T3 significantly reduced the growth of the two varieties under drought stress. Similarly, among the various drought-hardening treatments, T3 improved both the enzymatic (POD, CAT, APX) and non-enzymatic (AsA) defense systems along with the elevated levels of proline and soluble sugar to mitigate the negative effects of oxidative damage and bringing osmoregulation in tobacco plants. Finally, the various drought-hardening treatments (T1, T2, and T3) showed differential regulation of genes expressed in the two varieties, while, particularly T3 drought-hardening treatment-induced drought tolerance via the expression of various stress-responsive genes by triggering the biosynthesis pathways of proline (P5CS1), polyamines (ADC2), ABA-dependent (SnRK2, AREB1), and independent pathways (DREB2B), and antioxidant defense-related genes (CAT, APX1, GR2) in response to drought stress.ConclusionsDrought-hardening made significant contributions to drought tolerance and adaptation in two tobacco variety seedlings by reducing its growth and, on the other hand, by activating various defense mechanisms at biochemical and molecular levels. The findings of the study pointed out that drought-hardening is a fruitful strategy for conferring drought tolerance and adaptations in tobacco. It will be served as a useful method in the future to understand the drought tolerance and adaptation mechanisms of other plant species.Graphical abstractDrought-hardening improved drought tolerance and adaptation of the two tobacco varieties. T1 indicates drought-hardening for 24 h, T2 indicates drought-hardening for 48 h, T3 indicates drought-hardening for 72 h

The Central Negative Regulator of Flooding Tolerance, the PROTEOLYSIS 6 Branch of the N-degron Pathway, Adversely Modulates Salinity Tolerance in Arabidopsis.

Seawater intrusion in coastal regions and waterlogging in salinized lands are serious constraints that reduce crop productivity under changing climate scenarios. Under these conditions, plants encounter flooding and salinity concurrently or sequentially. Identification and characterization of genes and pathways associated with both flooding and salinity adaptation are critical steps for the simultaneous improvement of plant tolerance to these stresses. The PROTEOLYSIS 6 (PRT6) branch of the N-degron pathway is a well-characterized process that negatively regulates flooding tolerance in plants. Here, we determined the role of the PRT6/N-degron pathway in salinity tolerance in Arabidopsis. This study demonstrates that the prt6 mutation enhances salinity tolerance at the germination, seedling, and adult plant stages. Maintenance of chlorophyll content and root growth under high salt in the prt6 mutant was linked with the restricted accumulation of sodium ions (Na+) in shoots and roots of the mutant genotype. The prt6 mutation also stimulated mRNA accumulation of key transcription factors in ABA-dependent and independent pathways of osmotic/salinity tolerance, accompanied by the prominent expression of their downstream genes. Furthermore, the prt6 mutant displayed increased sensitivity to ethylene and brassinosteroids, which can suppress Na+ uptake and promote the expression of stress-responsive genes. This study provides genetic evidence that both salinity and flooding tolerance is coordinated through a common regulatory pathway in Arabidopsis.

Abscisic acid-mimicking ligand AMF4 induced cold tolerance in wheat by altering the activities of key carbohydrate metabolism enzymes

AMF4, a recently synthetic ABA-mimicking ligand, has been reported to have long-lasting effects in inducing the expression of stress-responsive genes, hence conferring abiotic tolerance in plants. To test the effect of AMF4 on cold tolerance induction, the wheat plants were firstly foliar sprayed with AMF4 (10 μM), then the AMF4 treated and the control plants were exposed to a 24-h low temperature treatment (2/0 °C). Under low temperature stress, the AMF plants possessed significantly higher relative water content, membrane stability index and ATP concentration in leaf, while lower leaf H2O2 concentration, compared with the control plants. The AMF4 treatment significantly increased the activities of APX, Ca2+-ATPase in the chloroplasts, while decreased SOD activity under low temperature, in relation to the control plants. In addition, the AMF plants showed significantly higher activities of key carbohydrate metabolism enzymes, such as UDP-glucose pyrophorylase, hexokinase, fructokinase, ADP-Glucose pyrophosphorylase, phosphoglucomutase, glucose-6-phosphate dehydrogenase and phosphoglucoisomerase, in relation to the control plants under low temperature. These results demonstrate that AMF4 could be used to induce cold tolerance in wheat, and provide novel insights into the potential ways to enhance abiotic stress tolerance using the synthetic ABA-mimicking ligands.

Molecular evaluation of quorum quenching potential of vanillic acid against Yersinia enterocolitica through transcriptomic and in silico analysis.

Introduction. Yersinia enterocolitica is one of the leading food-borne entero-pathogens causing various illnesses ranging from gastroenteritis to systemic infections. Quorum sensing (QS) is one of the prime mechanisms that control the virulence in Y. enterocolitica.Hypothesis/Gap Statement. Vanillic acid inhibits the quorum sensing and other virulence factors related to Y. enterocolitica. It has been evaluated by transcriptomic and Insilico analysis. Therefore, it can be a prospective agent to develop a therapeutic combination against Y. enterocolitica.Aim. The present study is focused on screening natural anti-quorum-sensing agents against Y. enterocolitica. The effect of selected active principle on various virulence factors was evaluated.Methodology. In total, 12 phytochemicals were screened by swarming assay. MATH assay, EPS and surfactant production assay, SEM analysis, antibiotic and blood sensitivity assay were performed to demonstrate the anti-virulence activity. Further, RNA sequencing and molecular docking studies were carried out to substantiate the anti-QS activity.Results. Vanillic acid (VA) has exhibited significant motility inhibition, thus indicating the anti-QS activity with MQIC of 400 µg ml-1 without altering the cell viability. It has also inhibited the violacein production in Chromobacterium violaceum ATCC 12472, which further confirms the anti-QS activity. VA has inhibited 16 % of cell-surface hydrophobicity (CSH), 52 % of EPS production and 60 % of surfactant production. Moreover, it has increased the sensitivity of Y. enterocolitica towards antibiotics. It has also made the cells upto 91 % more vulnerable towards human immune cells. The transcriptomic analysis by RNA sequencing revealed the down regulation of genes related to motility, virulence, chemotaxis, siderophores and drug resistance. VA treatment has also positively regulated the expression of several stress response genes. In furtherance, the anti-QS potential of VA has been validated with QS regulatory protein YenR by in silico molecular simulation and docking study.Conclusion. The present study is possibly the first attempt to demonstrate the anti-QS and anti-pathogenic potential of VA against Y. enterocolitica by transcriptomic and in silico analysis. It also deciphers that VA can be a promising lead to develop biopreservative and therapeutic regimens to treat Y. enterocolitica infections.

An OsNAM gene plays important role in root rhizobacteria interaction in transgenic Arabidopsis through abiotic stress and phytohormone crosstalk.

Overexpression of Bacillus amyloliquefaciens SN13-responsive OsNAM gene in Arabidopsis reveals its important role in beneficial plant and plant growth promoting rhizobacteria interaction by conferring stress tolerance and phytohormone modulation. Salinity is one of the major constraints that affect crop development and yield. Plants respond and adapt to salt stress via complex mechanisms that involve morpho-physiological, biochemical, and molecular changes. The expression of numerous genes is known to alter during various abiotic stresses and impart stress tolerance. Recently, some known rhizospheric microbes have also been used to mitigate the effects of abiotic stresses; however, the molecular basis of such interactions remains elusive. Therefore, the present investigation was aimed to elucidate the plant growth-promoting rhizobacteria (PGPR; Bacillus amyloliquefaciens-SN13) -induced crosstalk among salinity and phytohormones in OsNAM-overexpressed Arabidopsis plants. Transgenic plants showed increased germination percentage compared to wild-type (WT) seeds under 100mM of NaCl. Phenotypic data showed increased root length, rosette diameter, leaf size, and biomass in transgenics than WT plants. Transgenic plants can also better maintain membrane integrity and osmolyte concentration under salinity as compared to WT. Further, gene expression analysis of AP2/ERF, GST, ERD4, and ARF2 genes showed differential expression and their positive modulation in transgenic Arabidopsis exposed to salt stress in the presence of SN13 as compared to uninoculated WT. Modulation in IAA, ABA, and GA content in inoculated plants showed the more pronounced positive effects of SN13 on transgenic plants that supported our findings on Arabidopsis-SN13 interaction. Overall, the study concludes that SN13 positively modulated expression of stress-responsive genes under salinity and alter phytohormones levels in OsNAM-overexpressed plants suggesting its extensive role in cross-talk among salinity and phytohormones in response to PGPR.

Identification and characterization of multiple abiotic stress tolerance genes in wheat.

Wheat is produced worldwide over six continents with the European Union, China, India, Russia, and the United States as major producer countries. The productivity was recorded 749 million tons by harvesting from 220-million-hectare land. It is the need of the hour to develop stress-tolerant wheat varieties to enhance the productivity by 60% to provide food security to 9.6 billion-world population by 2050. Although the genotypes have been identified for heat, drought and salt tolerance, their underlying mechanism for tolerance is poorly understood. The detailed understanding of the mechanism and identification of critical factors participating in multiple abiotic stress tolerance is essential. In the present study, the contrasting wheat genotypes were intensely characterized and assessed for the expression of different stress responsive genes under lab conditions. The expression analysis revealed that SHN1, DREB6, NHX2 and AVP1 were found to be highly induced under heat, salt and drought stresses in wheat. Thus, these genes can be used as signature genes to identify the multiple stress-tolerant varieties in the breeding program. The novel variants of these genes can be targeted through breeding or genetic engineering or genome editing strategies to develop multiple abiotic stress tolerant wheat varieties.

Structure-function relationship of Gossypium hirsutum NAC transcription factor, GhNAC4 with regard to ABA and abiotic stress responses

Our previous study demonstrated that the expression of GhNAC4, a NAC transcription factor from cotton, was induced by abiotic stresses and abscisic acid (ABA). In the present study, we investigated the molecular mechanisms underlying ABA and stress response of GhNAC4. Overexpression of GhNAC4 in transgenic tobacco conferred tolerance to salinity and drought treatments with associated enhanced expression of several stress-responsive marker genes. GhNAC4 is a protein that is translocated to the nucleus where it exhibits transcriptional activation property and also forms homo-dimers. In this study, we also investigated the domains essential for the biochemical functions of GhNAC4. We developed transgenic tobacco plants overexpressing the GhNAC4 NAC-domain and the transcriptional regulatory (TR) domain separately. NAC-domain transgenics showed hypersensitivity to exogenous ABA while TR-domain transgenics exhibited reduced sensitivity. Abiotic stress assays indicated that transgenic plants expressing both the domains separately were more tolerant than wild type plants with the NAC-domain transgenics showing increased tolerance as compared to TR-domain transgenics. Expression analysis revealed that various stress-responsive genes were upregulated in both NAC-domain and TR-domain transgenics under salinity and drought treatments. These results suggest that the stress tolerance ability of GhNAC4 is associated with both the component domains while the ABA responsiveness is largely associated with N-terminal NAC-domain.

Identification of genome-wide targets and DNA recognition sequence of the Arabidopsis HMG-box protein AtHMGB15 during cold stress response

AtHMGB15 belongs to a group of ARID-HMG proteins which are plant specific. The presence of two known DNA binding domains: AT rich interacting domain (ARID) and High Mobility Group (HMG)-box, in one polypeptide, makes this protein intriguing. Although proteins containing individual HMG and ARID domains have been characterized, not much is known about the role of ARID-HMG proteins. Promoter analysis of AtHMGB15 showed the presence of various stress responsive cis regulatory elements along with MADS-box containing transcription factors. Our result shows that the expression of AtHMGB15 increased significantly upon application of cold stress. Using ChIP-chip approach, we have identified 6128 and 4689 significantly enriched loci having AtHMGB15 occupancy under control and cold stressed condition respectively. GO analysis shows genes belonging to abiotic stress response, cold response and root development were AtHMGB15 targets during cold stress. DNA binding and footprinting assays further identified A(A/C)--ATA---(A/T)(A/T) as AtHMGB15 binding motif. The enriched probe distribution in both control and cold condition shows a bias of AtHMGB15 binding towards the transcribed (gene body) region. Further, the expression of cold stress responsive genes decreased in athmgb15 knockout plants compared to wild-type. Taken together, binding enrichment of AtHMGB15 to the promoter and upstream to stress loci suggest an unexplored role of the protein in stress induced transcription regulation.

Differences in Postmating Transcriptional Responses between Conspecific and Heterospecific Matings in Drosophila.

In many animal species, females undergo physiological and behavioral changes after mating. Some of these changes are driven by male-derived seminal fluid proteins and are critical for fertilization success. Unfortunately, our understanding of the molecular interplay between female and male reproductive proteins remains inadequate. Here, we analyze the postmating response in a Drosophila species that has evolved strong gametic incompatibility with its sister species; Drosophila novamexicana females produce only ∼1% fertilized eggs in crosses with Drosophila americana males, compared to ∼98% produced in within-species crosses. This incompatibility is likely caused by mismatched male and female reproductive molecules. In this study, we use short-read RNA sequencing to examine the evolutionary dynamics of female reproductive genes and the postmating transcriptome response in crosses within and between species. First, we found that most female reproductive tract genes are slow-evolving compared to the genome average. Second, postmating responses in con- and heterospecific matings are largely congruent, but heterospecific matings induce expression of additional stress-response genes. Some of those are immunity genes that are activated by the Imd pathway. We also identify several genes in the JAK/STAT signaling pathway that are induced in heterospecific, but not conspecific mating. While this immune response was most pronounced in the female reproductive tract, we also detect it in the female head and ovaries. These results show that the female’s postmating transcriptome-level response is determined in part by the genotype of the male, and that divergence in male reproductive genes and/or traits can have immunogenic effects on females.

Role of Secondary Oxidative Stress in the Bactericidal Action of Antibiotics

Exposure to β-lactam, fluoroquinolone, and aminoglycoside antibiotics caused an increase in the production of hydrogen peroxide and the expression of OxyR-regulon of the oxidative stress response in Escherichia coli cells. Under the conditions of microaeration, the attenuation of secondary oxidative stress due to the addition of the antioxidant thiourea influenced the antibacterial effect of fluoroquinolones. Thiourea potentiated the effect of sublethal (not decreasing the number of colony-forming units below 103/mL) doses of the antibiotic and increased the viability of cells exposed to lethal doses. The addition of thiourea reduced the expression of OxyR-regulon activated by the sublethal action of the antibiotic to the level of antibiotic-free culture. When exposed to lethal doses, a decrease in the antibiotic-mediated expression of oxidative stress response genes in the presence of thiourea was also observed; however, the expression level remained higher compared to antibiotic-free culture. This may indicate the dual role of ROS under antibiotic treatment as the damaging agents contributing to cell death and as signal molecules activating stress responses.

Over-expression of rice R1-type MYB transcription factor confers different abiotic stress tolerance in transgenic Arabidopsis

Among various abiotic stresses, water deficit hit the first in the list followed by heavy metal stresses as a serious environmental growth-limiting factor that restricts the global crop yield. Molecular approaches will help us to trace key regulators which are involved in stress-related phenomenon to enhance crop productivity. The present study functionally characterized one of the key regulators, OsMYB-R1 in Arabidopsis. Phylogenetic analyses indicated that OsMYB-R1 had a close relationship with Sorghum bicolour and Zea mays. Ectopic expression of OsMYB-R1 in Arabidopsis resulted in improved tolerance to PEG/drought and chromium stress in addition to conferring no tolerance to salinity stress. Further RNA seq. data revealed that OsMYB-R1 regulates the expression of key genes that improve the root architecture and maintain the cellular homeostasis of transgenic lines through an efficient anti-oxidant system. It also reveals the differential gene expression of stress-responsive and hormone-responsive genes, which indicate the intricate network of defense regulatory machinery activated in transgenic lines. Additionally, salicylic acid (SA) plays a significant role in promoting the growth of the OsMYB–R1 over-expressing plants and increased GUS intensity in SA treated OsMYB–R1 promoter plants demonstrate the explicit role of SA signaling in overcoming stress tolerance. Whereas no significant change was observed in OsMYB–R1 over-expressing plants after ABA and MeJA treatment. Overall, OsMYB-R1 is a promising gene resource for improving abiotic stress tolerance in other crops, especially in dicotyledon plants.

Delivery room skin-to-skin contact in preterm infants affects long-term expression of stress response genes

Premature birth is a traumatic event that puts mother and child at risk for subsequent psychopathology. Skin-to-skin contact in the form of intermittent kangaroo mother care has been shown to positively affect the infant’s stress response and cognitive development, but underlying mechanisms remain unclear. Moreover, first skin-to-skin contact is usually delayed for days after birth.In the delivery room skin-to-skin study (DR-SSC), a prospective randomized controlled trial conducted from 2/2012 to 7/2015, we set out to assess the effect of delivery room skin-to-skin contact on the infant’s mRNA expression of six key molecules involved in stress response and neurobehavioral development at hospital discharge. 88 firstborn, singleton preterm infants (born at 25–32 weeks of gestational age) were included. In the delivery room after initial stabilization, infants were randomized to either 60 min of skin-to-skin or 5 min of visual contact with their mother. In this explorative add-on study on the original DR-SSC study, we determined the expression of six important stress response genes (CRHR1 and CRHR2, AVP, NR3C1, HTR2A, and SLC6A4) in peripheral white blood cells of infants during routine blood sampling upon hospital discharge (corrected gestational age of 40 weeks). Infants were followed up to six months corrected age.Relative mRNA expression of the corticotropin releasing hormone receptor 2 (CRH R2), the glucocorticoid receptor gene (NR3C1), and the serotonin transporter gene (SLC6A4) was significantly reduced in the delivery room SSC infants. Additionally, gene expression of CRH R2 showed a correlation with HPA axis reactivity and parameters of mother-child interaction at six months corrected age.Our results highlight the importance of delivery room mother-child skin-to-skin contact and underline the urgent need for in-depth studies on the underlying molecular mechanisms.

Overexpression of AlNAC1 from recretohalophyte Aeluropus lagopoides alleviates drought stress in transgenic tobacco

Drought greatly limits agricultural yield worldwide. The NAC transcription factors play important role during plant growth, development and ABA dependent/independent stress regulation. The AlNAC1 from Aeluropus lagopoides (Poaceace, halophyte) encodes 375 amino acids and gets clustered with NAC TFs from monocots. In-silico analysis showed that it contains bipartite nuclear localization sequence within the conserved NAC domain, post-translational modification sites and belongs to NAM sub-family. The recombinant AlNAC1 protein binds to NACRS cis-element of erd1 promoter. The overexpression of AlNAC1 in transgenic tobacco enhanced drought tolerance, which can be attributed to increased photosynthetic pigments, membrane stability, osmoprotectants, antioxidative enzyme activity and reduced accumulation of reactive oxygen species. Also, AlNAC1 transgenics showed improved water use efficiency, electron transport rate and chlorophyll fluorescence related photosynthetic parameters (Fv/Fm, photochemical and non-photochemical quenching and ФPSII) during drought. Interestingly, AlNAC1 transgenics showed increased number of closed stomata during drought that can be correlated to the enhanced endogenous abscisic acid (ABA), indicating ABA-regulated stomatal movement in transgenics. Furthermore, expression of stress-responsive (P5CS, LTP1 and CAT) and photosynthesis-related (Rca1 and Cab40) genes were upregulated. Thus, the present study suggest that AlNAC1 might work in an ABA-dependent manner to alleviate drought stress by regulating stomatal movement, photosynthesis and reduce oxidative damage in transgenics.

AgNAC1, a celery transcription factor, related to regulation on lignin biosynthesis and salt tolerance

The NAC transcription factor participates in various biotic and abiotic stress responses and plays a critical role in plant development. Lignin is a water-insoluble dietary fiber, but it is second only to cellulose in abundance. Celery is the main source of dietary fiber, but its quality and production are limited by various abiotic stresses. Here, AgNAC1 containing the NAM domain was identified from celery. AgNAC1 was found to be a nuclear protein. Transgenic Arabidopsis thaliana plants hosting AgNAC1 have longer root lengths and stomatal axis lengths than the wide type (WT). The evidence from lignin determination and expression levels of lignin-related genes indicated that AgNAC1 plays a vital role in lignin biosynthesis. Furthermore, the results of the physiological characterization and the drought and salt treatments indicate that AgNAC1-overexpressing plants are significantly resistive to salt stress. Under drought and salt treatments, the AgNAC1 transgenic Arabidopsis thaliana plants presented increased superoxide dismutase (SOD) and peroxidase (POD) activities and decreased malondialdehyde (MDA) content and size of stomatal apertures relatively to the WT plants. The AgNAC1 served as a positive regulator in inducing the expression of stress-responsive genes. Overall, the overexpressing AgNAC1 enhanced the plants' resistance to salt stress and played a regulatory role in lignin accumulation.

The Arabidopsis sucrose non-fermenting-1-related protein kinase AtSnRK2.4 interacts with a transcription factor, AtMYB21, that is involved in salt tolerance

Sucrose non-fermenting-1-related protein kinase 2 s (SnRK2 s) are important stress-related plant protein kinases in plants. The interaction partners and phosphorylation substrates of group II and III SnRK2 s in Arabidopsis thaliana have been identified, but similar data for group I SnRK2 s are very limited. Here, we used a yeast two-hybrid (Y2H) screen to find proteins that interact with Arabidopsis AtSnRK2.4, a group I SnRK2. The transcription factor AtMYB21 was identified as an AtSnRK2.4 interaction partner, and its interaction with AtSnRK2.4 was confirmed by an in vitro pull-down assay and a bimolecular fluorescence complementation (BiFC) assay. A subcellular localization assay demonstrated that AtSnRK2.4 and AtMYB21 were located in the cytoplasm and nucleus of onion epidermal cells. AtSnRK2.4 and AtMYB21 were expressed in many tissues and upregulated in response to NaCl stress. Transgenic plants that overexpressed AtSnRK2.4 or AtMYB21 gene exhibited enhanced tolerance to salt stress at germination and post-germination stages. Moreover, the expression of downstream stress-responsive genes was upregulated in salt-stressed AtSnRK2.4 and AtMYB21 transgenic Arabidopsis. These results suggest that AtSnRK2.4 may act synergistically with AtMYB21 to mediate the response to salt stress through the upregulation of downstream stress-responsive genes.

Overexpression of wheat transcription factor (TaHsfA6b) provides thermotolerance in barley.

Overexpressing a heat shock factor gene (TaHsfA6bT) from wheat provides thermotolerance in barley by constitutive expression of heat and other abiotic stress-response genes. Temperature is one of the most crucial abiotic factors defining the yield potential of temperate cereal crops, such as barley. The regulators of heat shock response (HSR), heat stress transcription factors (Hsfs), modulate the transcription level of heat-responsive genes to protect the plants from heat stress. In this study, an Hsf from wheat (TaHsfA6b) is overexpressed in barley for providing thermotolerance. Transgenic barley lines overexpressing TaHsfA6b showed improvement in thermotolerance. The constitutive overexpression of a TaHsfA6b gene upregulated the expression of major heat shock proteins and other abiotic stress-responsive genes. RNA-seq and qRT-PCR analysis confirmed the upregulation of Hsps, chaperonins, DNAJ, LEA protein genes, and genes related to anti-oxidative enzymes in transgenic lines. Excessive generation and accumulation of reactive oxygen species (ROS) occurred in wild-type (WT) plants during heat stress; however, the transgenic lines reflected improved ROS homeostasis mechanisms, showing lesser ROS accumulation under high temperature. No negative phenotypic changes were observed in overexpression lines. These results suggest that TaHsfA6b is a regulator of HSR and its overexpression altered the expression patterns of some main stress-related genes and enhanced the thermotolerance of this cereal crop.

Translational induction of ATF4 during integrated stress response requires noncanonical initiation factors eIF2D and DENR

The Integrated Stress Response (ISR) helps metazoan cells adapt to cellular stress by limiting the availability of initiator methionyl-tRNA for translation. Such limiting conditions paradoxically stimulate the translation of ATF4 mRNA through a regulatory 5′ leader sequence with multiple upstream Open Reading Frames (uORFs), thereby activating stress-responsive gene expression. Here, we report the identification of two critical regulators of such ATF4 induction, the noncanonical initiation factors eIF2D and DENR. Loss of eIF2D and DENR in Drosophila results in increased vulnerability to amino acid deprivation, susceptibility to retinal degeneration caused by endoplasmic reticulum (ER) stress, and developmental defects similar to ATF4 mutants. eIF2D requires its RNA-binding motif for regulation of 5′ leader-mediated ATF4 translation. Consistently, eIF2D and DENR deficient human cells show impaired ATF4 protein induction in response to ER stress. Altogether, our findings indicate that eIF2D and DENR are critical mediators of ATF4 translational induction and stress responses in vivo.

The Endogenous Tryptophan-derived Photoproduct 6-formylindolo[3,2-b]carbazole (FICZ) is a Nanomolar Photosensitizer that Can be Harnessed for the Photodynamic Elimination of Skin Cancer Cells in Vitro and in Vivo.

UV-chromophores contained in human skin may act as endogenous sensitizers of photooxidative stress and can be employed therapeutically for the photodynamic elimination of malignant cells. Here, we report that 6-formylindolo[3,2-b]carbazole (FICZ), a tryptophan-derived photoproduct and endogenous aryl hydrocarbon receptor agonist, displays activity as a nanomolar sensitizer of photooxidative stress, causing the photodynamic elimination of human melanoma and nonmelanoma skin cancer cells in vitro and in vivo. FICZ is an efficient UVA/Visible photosensitizer having absorbance maximum at 390nm (ε=9180L mol-1 cm-1 ), and fluorescence and singlet oxygen quantum yields of 0.15 and 0.5, respectively, in methanol. In a panel of cultured human squamous cell carcinoma and melanoma skin cancer cells (SCC-25, HaCaT-ras II-4, A375, G361, LOX), photodynamic induction of cell death was elicited by the combined action of solar simulated UVA (6.6Jcm-2 ) and FICZ (≥10nm), preceded by the induction of oxidative stress as substantiated by MitoSOX Red fluorescence microscopy, comet detection of Fpg-sensitive oxidative genomic lesions and upregulated stress response gene expression (HMOX1, HSPA1A, HSPA6). In SKH1 "high-risk" mouse skin, an experimental FICZ/UVA photodynamic treatment regimen blocked the progression of UV-induced tumorigenesis suggesting feasibility of harnessing FICZ for the photooxidative elimination of malignant cells in vivo.

Overexpression of ThMYB8 mediates salt stress tolerance by directly activating stress-responsive gene expression

MYB transcription factors are important in abiotic stress responses; however, the detailed mechanisms are unclear. Tamarix hispida contains multiple MYB genes. The present study characterized T. hispida MYB8 (ThMYB8) during salt stress using transgenic T. hispida and Arabidopsis assays. ThMYB8 overexpression and ThMYB8 RNAi analysis demonstrated that ThMYB8 enhanced the salt stress tolerance. Transgenic Arabidopsis ectopic expression of ThMYB8 significantly increased root growth, fresh weight, and seed germination rate compared with that of the wild-type under salt stress. Physiological parameters analysis in T. hispida and Arabidopsis showed that ThMYB8 overexpressing plants had the lowest levels of O2, H2O2, cell death, malondialdehyde, and electrolyte leakage. Overexpression of ThMYB8 regulated Na+ and K+ concentrations in plant tissues while maintaining K+/Na+ homeostasis. Analysis using qRT-PCR and ChIP-PCR identified possible downstream ThMYB8-regulated genes. ThMYB8 regulated the expression of ThCYP450-2 (cytochrome p450-2), Thltk (leucine-rich repeat transmembrane protein kinase), and ThTIP (aquaporin TIP) by binding to the MBSI motif (‘CAACTG’) in their promoters. The results indicated that ThMYB8 enhanced salt stress tolerance in T. hispida by regulating gene expression related to the activation of stress-associated physiological changes, such as enhanced reactive oxygen species scavenging capability, maintaining K+/Na+ homeostasis, and decreasing the malondialdehyde content and lipid peroxidation cell membranes.