TaWRKY31, a novel WRKY transcription factor in wheat, participates in regulation of plant drought stress tolerance

BACKGROUND

Wheat, a crucial food crop in China, is highly vulnerable to drought stress throughout its growth and development. WRKY transcription factors (TFs), being one of the largest families of TFs, play a vital role in responding to various abiotic stresses in plants.

RESULTS

Here, we cloned and characterized the TF TaWRKY31 isolated from wheat. This TF, belonging to the WRKY II family, contains a WRKYGQK amino acid sequence and a C2H2-type zinc finger structure. TaWRKY31 exhibits tissue-specific expression and demonstrates responsiveness to abiotic stresses in wheat. TaWRKY31 protein is localized in the nucleus and can function as a TF with transcription activating activity at the N-terminus. Results showed that the wheat plants with silenced strains (BSMV:TaWRKY31-1as and BSMV:TaWRKY31-2as) exhibited poor growth status and low relative water content when subjected to drought treatment. Moreover, the levels of O2·-, H2O2, and malondialdehyde (MDA) in the BSMV:TaWRKY31-induced wheat plants increased, while the activities of antioxidant enzymes (superoxide dismutase, peroxidase, and catalase) decreased. Compared to control plants, BSMV:TaWRKY31-induced wheat plants exhibited lower expression levels of TaSOD (Fe), TaPOD, TaCAT, TaDREB1, TaP5CS, TaNCED1, TaSnRK2, TaPP2C, and TaPYL5.Under stress or drought treatment conditions, the overexpression of TaWRKY31 in Arabidopsis resulted in decreased levels of H2O2 and MDA, as well as reduced stomatal opening and water loss. Furthermore, an increase in resistance oxidase activity, germination rate, and root length in the TaWRKY31 transgenic Arabidopsis was observed. Lastly, overexpression of TaWRKY31 in Arabidopsis resulted in higher the expression levels of AtNCED3, AtABA2, AtSnRK2.2, AtABI1, AtABF3, AtP5CS1, AtSOD (Cu/Zn), AtPOD, AtCAT, AtRD29A, AtRD29B, and AtDREB2A than in control plants.

CONCLUSIONS

Our findings indicate that TaWRKY31 enhances drought resistance in plants by promoting the scavenging of reactive oxygen species, reducing stomatal opening, and increasing the expression levels of stress-related genes.

Comparative transcriptomic profiling reveals differentially expressed genes and important related metabolic pathways in shoots and roots of a Saudi wheat cultivar (Najran) under salinity stress

High salinity of soil is a threatening constraint for agricultural output worldwide. The adverse effects of salt stress on plants can be revealed in different manners, from phenotypic to genetic changes. A comparative RNA-Sequencing analysis was done in roots and shoots of bread wheat, Najran cultivar between plants grown under unstressed control condition (0 mM NaCl) and salt treatment (200 mM NaCl). More than 135 million and 137 million pair-end reads were obtained from root and shoot samples, respectively. Of which, the mapped reads to Triticum aestivum genome IWGSC_V51 ranged from 83.9% to 85% in the root and 71.6% to 79% in the shoot. Interestingly, a comparison of transcriptomic profiling identified that total number of significantly differentially expressed genes (DEGs) examined in the roots was much higher than that found in the shoots under NaCl treatment, 5829 genes were differentially expressed in the roots whereas 3495 genes in the shoots. The salt-induced change in the transcriptome was confirmed by RT-qPCR using a set of randomly selected genes. KEGG enrichment analysis classified all DEGs in both roots and shoots into 25 enriched KEGG pathways from three main KEGG classes: Metabolism, organismal systems and genetic information processing. According to that, the most significantly regulated pathways in the root and shoot tissues were glutathione metabolism and biosynthesis of secondary metabolites such as phenylpropanoids and galactose metabolism suggesting that these pathways might participate in wheat salt tolerance. The findings highlight the importance of the control of oxidative stress via Glutathione and phenylpropanoids and the regulation of galactose metabolism in the roots and shoots for salt-tolerance in wheat. They open promising prospects for engineering salt-tolerance in this important crop via targeted improvement of the regulation of key genes in the production of these compounds.

Foliar Applied Acetylsalicylic Acid Induced Growth and Key-Biochemical Changes in Chickpea (Cicer arietinum L.) Under Drought Stress

The exogenous application of acetylsalicylic acid (ASA) is stated to increase tolerance of plants against different environmental stresses. Therefore, the present study was planned to get insight into ASA-mediated regulation of growth, secondary metabolism, and oxidative defense in 2 chickpea varieties. Ten seeds of 2 chickpea varieties (DG-89 and Bittle-98) were sown in plastic pots containing sandy loam soil with 3 drought stress levels, i.e. wet conditions or flooded water (100% FC) as recommended control, 75% FC, 50% FC and 25% FC for chickpea. The moisture contents were maintained and regularly monitored through the addition of normal irrigation water. The design of experimental was completely randomized with 3 replicates per treatment. Penultimate leaves were harvested with knife after 20 days of foliar spray to observe the effect of exogenously applied ASA (100 mg/L) on growth, and key-biochemical attributes of chickpea plants (DG-89 and Bittle-98) under drought stress regimes. Drought stress regimes caused a substantial decline in shoot (37% and 35%) and root length (67% and 78%), shoot (80% and 76%) and root (62% and 68%) fresh masses, shoot (71% and 63%) and root (77% and 74%) dry masses, leaf area per plant (77% and 80%), chlorophyll a (7% and 45%), chlorophyll b (57% and 42%), total chlorophyll (30% and 39%), total carotenoids (76% and 54%), total anthocyanins (38%), reducing sugar (10% and 57%), total soluble proteins (77% and 44%), total flavonoids (61% and 59%) and total phenolics (58% and 31%) contents in both DG-89 and Bittle-98, respectively. A significant increase in MDA (25%), H₂O₂ contents (100% and 62%), proline (145% and 131%), and ascorbic acid (133% and 203%) contents was documented in stressed plants of both varieties, respectively. Additionally, drought stress significantly improved the activities of POD (154% and 76%), CAT (87% and 45%) and SOD (248% and 143%) in both varieties. Exogenous application of ASA reduced drought-mediated oxidative stress by reducing MDA (53% and 14%), and H₂O₂ (84% and 56%) contents, proline contents (50% and 17%) and enhanced the shoot (6% and 25%) and root (43% and 33%) dry masses, leaf area (9% and 10%), chlorophyll a (7% and 32%), b (82% and 81%), and carotenoids (53% and 33%) in both barley cultivars. When plants of chickpea was treated with ASA had greater total anthocyanins (26% and 35%), free amino acids (48% and 28%), ascorbic acid contents (135% and 179%), total soluble proteins (34% and 23%), total flavonoids (58% and 35%) and phenolic (50% and 69%)contents besides the POD (41% and 64%), CAT (23% and 56%) and SOD (73% and 72%) enzymes activities. Plants of DG-89 showed more tolerance to drought stress than that of Bittle-98 as a manifest from higher plant biomasses. Thus, our results showed that foliar-applied ASA is an effective strategy that can be used to improve the tolerance of chickpea plants to drought stress.

Effect of Fluoride on Germination, Early Growth and Antioxidant Enzymes Activity of Three Winter Wheat (Triticum aestivum L.) Cultivars

This paper assesses the impact of sodium fluoride on the morphological parameters and activity of catalase and peroxidase during the germination and root growth phases of three winter wheat cultivars: Tobak, Dalewar, and Arkadia. During examination, the seeds were placed on plastic Petri dishes with an NaF solution at concentrations of 0 (control), 2.5, 5.0, 8.0, and 10.0 mmol dm−3. The obtained results have shown a decrease in germination, inhibition of root growth, and inhibition of catalase activity, both in the embryos and roots of all tested winter wheat cultivars. The observed effects have been strengthened with the increase of the fluoride concentration. However, the effect of NaF on the peroxidase activity has been dependent on the wheat cultivar. It is difficult to state unequivocally which of the tested winter wheat cultivars has been characterized by the highest sensitivity to fluoride. An η2 analysis has confirmed that the NaF concentration has a greater effect than the winter wheat cultivar on the activity of the determined antioxidant enzymes.

Comparative Transcriptome Analysis of Halophyte Zoysia macrostachya in Response to Salinity Stress

As one of the most severe environmental stresses, salt stress can cause a series of changes in plants. In salt tolerant plant Zoysia macrostachya, germination, physiology, and genetic variation under salinity have been studied previously, and the morphology and distribution of salt glands have been clarified. However, no study has investigated the transcriptome of such species under salt stress. In the present study, we compared transcriptome of Z. macrostachya under normal conditions and salt stress (300 mmol/L NaCl, 24 h) aimed to identify transcriptome responses and molecular mechanisms under salt stress in Z. macrostachya. A total of 8703 differently expressed genes (DEGs) were identified, including 4903 up-regulated and 3800 down-regulated ones. Moreover, a series of molecular processes were identified by Gene Ontology (GO) analysis, and these processes were suggested to be closely related to salt tolerance in Z. macrostachya. The identified DEGs concentrated on regulating plant growth via plant hormone signal transduction, maintaining ion homeostasis via salt secretion and osmoregulatory substance accumulation and preventing oxidative damage via increasing the activity of ROS (reactive oxygen species) scavenging system. These changes may be the most important responses of Z. macrostachya under salt stress. Some key genes related to salt stress were identified meanwhile. Collectively, our findings provided valuable insights into the molecular mechanisms and genetic underpinnings of salt tolerance in Z. macrostachya.

Defense responses of wheat plants (Triticum aestivum L.) against brown spot as a result of possible elicitors application

ABSTRACT: The objective of this research was to evaluate the response of wheat plants to the application of possible elicitor compounds against Bipolaris sorokiniana pathogen. This response was measured through the quantification of antioxidant enzymes, malondialdehyde and flavonoids, evaluation of the severity of brown spot disease and productivity in wheat, greenhouse and field crops. The treatments consisted of suspensions of endophytic fungi Aspergillus japonicus and Trichoderma tomentosum, salicylic acid, acibenzolar-S-methyl and fungicide. In the field trials, in 2015 and 2016, the development of the disease was lower and productivity was higher in all treatments, with emphasis on the fungicide. However, endophytic fungi suspensions demonstrated potential as growth promoters, disease severity reducers and protective antioxidant response activators, as they promoted significant increase in superoxide dismutase, catalase, glutathione and flavonoid enzymes.

Antioxidant responses of wheat plants under stress

Currently, food security depends on the increased production of cereals such as wheat (Triticum aestivum L.), which is an important source of calories and protein for humans. However, cells of the crop have suffered from the accumulation of reactive oxygen species (ROS), which can cause severe oxidative damage to the plants, due to environmental stresses. ROS are toxic molecules found in various subcellular compartments. The equilibrium between the production and detoxification of ROS is sustained by enzymatic and nonenzymatic antioxidants. In the present review, we offer a brief summary of antioxidant defense and hydrogen peroxide (H2O2) signaling in wheat plants. Wheat plants increase antioxidant defense mechanisms under abiotic stresses, such as drought, cold, heat, salinity and UV-B radiation, to alleviate oxidative damage. Moreover, H2O2 signaling is an important factor contributing to stress tolerance in cereals.

Medicinal plants contain mucilage used in traditional Persian medicine (TPM)

CONTEXT

Conventional therapies using mucilage plants greatly used by practitioners in Iran. The usage of mucilages is rooted in traditional knowledge with a history of more than 4000 years. Scientific assessment of these historical documents could be valuable for finding new potential usage in the current medicine.

OBJECTIVE

This study assembled an inventory of mucilage plants considered important therapeutic aids for alleviating the ailments in ancient Persian medicine and compared therapeutic applications of ancient times with current findings of medicinal mucilages in the same plant species.

METHODS

A literature search compiled some main traditional manuscripts of Persian medicine, including the book of AlHavi, Canon of Medicine, Zakhireh-iKharazmshahi, Qarabadine-kabir, Tohfat ol Moemenin, and Makhzan-ol-advieh, and select mucilage plants used in treating the mouth and respiratory system disorders. Also, current investigations on related subjects were considered through a search of the Pub Med and Google Scholar databases.

RESULTS

In Iran, the application of medicinal plants contains mucilage date back to ancient times. In mentioned medieval Persian books, 20 medicinal plants containing mucilage were identified. Mucilages have been traditionally used via oral or topical routes for a variety of disorders. According to this study, most of the cited medicinal plant species were used for their mucilaginous, anti-inflammatory, and anti-oxidant effects.

CONCLUSIONS

A scientific evaluation of these historical documents can give an insight into the ideas of the past and be valuable in finding new data on clinical use of the mucilages that should lead to future opportunities to investigate their potential medicinal use.

Salinity induced the changes of root growth and antioxidative responses in two wheat cultivars

This study aimed to investigate the inhibitory mechanism of root growth and to compare antioxidative responses in two wheat cultivars, drought-tolerant Ningchun and drought-sensitive Xihan, exposed to different NaCl concentrations. Ningchun exhibited lower germination rate, seedling growth, and lipid peroxidation than Xihan when exposed to salinity. The loss of cell viability was correlated with the inhibition of root growth induced by NaCl stress. Moreover, treatments with H2O2 scavenger dimethylthiourea and catalase (CAT) partly blocked salinity-induced negative effects on root growth and cell viability. Besides, the enhancement of superoxide radical and H2O2 levels, and the stimulation of CAT and diamine oxidase (DAO) as well as the inhibition of glutathione reductase (GR) were observed in two wheat roots treated with salinity. However, hydroxyl radical content increased only in Xihan roots under NaCl treatment, and the changes of soluble peroxidase (POD), ascorbate peroxidase (APX), superoxide dismutase (SOD), and cell-wall-bound POD activities were different in drought-tolerant Ningchun and drought-sensitive Xihan exposed to different NaCl concentrations. In conclusion, salinity might induce the loss of cell viability via a pathway associated with extracellular H2O2 generation, which was the primary reason leading to the inhibition of root growth in two wheat cultivars. Here, it was also suggested that increased H2O2 accumulation in the roots of drought-tolerant Ningchun might be due to decreased POD and GR activities as well as enhanced cell-wall-bound POD and DAO ones, while the inhibition of APX and GR as well as the stimulation of SOD and DAO was responsible for the elevation of H2O2 level in drought-sensitive Xihan roots.