Higher Proline Content Research Articles

Distinctive Physio-Biochemical Properties and Transcriptional Changes Unfold the Mungbean Cultivars Differing by Their Response to Drought Stress at Flowering Stage

Mungbean is a nutritionally and economically important pulse crop cultivated around Asia, mainly in India. The crop is sensitive to drought at various developmental stages of its growing period. However, there is limited or almost no research on a comparative evaluation of mung-bean plants at the flowering stage under drought conditions. Hence, the aim of this research was to impose the drought stress on two mungbean cultivars VRM (Gg) 1 and CO6 at the flowering stage and assess the physio-biochemical and transcriptional changes. After imposing the drought stress, we found that VRM (Gg) 1 exhibited a low reduction in physiological traits (Chlorophyll, relative water content, and plant dry mass) and high proline content than CO6. Additionally, VRM (Gg) 1 has a low level of H2O2 and MDA contents and higher antioxidant enzymes (SOD, POD, and CAT) activity than CO6 during drought stress. The transcriptional analysis of photosynthesis (PS II-PsbP, PS II-LHC, PS I-PsaG/PsaK, and PEPC 3), antioxidant (SOD 2, POD, CAT 2), and drought-responsive genes (HSP-90, DREB2C, NAC 3 and AREB 2) show that VRM (Gg) 1 had increased transcripts more than CO6 under drought stress. Taken together, VRM (Gg) 1 had a better photosynthetic performance which resulted in fewer reductions in chlorophyll, relative water content, and plant dry mass during drought stress. In addition, higher antioxidative enzyme activities led to lower H2O2 and MDA levels, limiting oxidative damage in VRM (Gg) 1. This was positively correlated with increased transcripts of photosynthesis and antioxidant-related genes in VRM (Gg) 1. Further, the increased transcripts of drought-responsive genes indicate that VRM (Gg) 1 has a better genetic basis against drought stress than CO6. These findings help to understand the mungbean response to drought stress and will aid in the development of genotypes with greater drought tolerance by utilizing natural genetic variants.

Molecular Cloning and Characterization of MbMYB108, a Malus baccata MYB Transcription Factor Gene, with Functions in Tolerance to Cold and Drought Stress in Transgenic Arabidopsis thaliana.

The MYB transcription factor (TF) family is one of the largest transcription families in plants, which is widely involved in the responses of plants to biotic and abiotic stresses, as well as plant growth, development, and metabolic regulation. In the present study, a new MYB TF gene, MbMYB108, from Malus baccata (L.) Borkh, was identified and characterized. The open reading frame (ORF) of MbMYB108 was found to be 903 bp, encoding 300 amino acids. Sequence alignment results and predictions of the protein structure indicated that the MbMYB108 protein contained the conserved MYB domain. Subcellular localization showed that MbMYB108 was localized to the nucleus. The expression of MbMYB108 was enriched in young and mature leaves, and was highly affected by cold and drought treatments in M. baccata seedlings. When MbMYB108 was introduced into Arabidopsis thaliana, it greatly increased the cold and drought tolerances in the transgenic plant. Increased expression of MbMYB108 in transgenic A. thaliana also resulted in higher activities of peroxidase (POD) and catalase (CAT), higher contents of proline and chlorophyll, while malondialdehyde (MDA) content and relative conductivity were lower, especially in response to cold and drought stresses. Therefore, these results suggest that MbMYB108 probably plays an important role in the response to cold and drought stresses in A. thaliana by enhancing the scavenging capability for reactive oxygen species (ROS).

PcWRKY11, an II-d WRKY Transcription Factor from Polygonum cuspidatum, Enhances Salt Tolerance in Transgenic Arabidopsis thaliana.

Being an invasive plant, Polygonum cuspidatum is highly resilient and can survive in unfavorable environments for long periods; however, its molecular mechanisms associated with such environmental resistance are largely unknown. In this study, a WRKY transcription factor (TF) gene, PcWRKY11, was identified from P. cuspidatum by analyzing methyl jasmonate (MeJA)-treated transcriptome data. It showed a high degree of homology with WRKY11 from Arabidopsis thaliana, containing a WRKY domain and a zinc finger structure and II-d WRKY characteristic domains of HARF, a calmodulin-binding domain (C-motif), and a putative nuclear localization signal (NLS) through sequence alignment and functional element mining. qPCR analysis showed that the expression of PcWRKY11 can be induced by NaCl, osmotic stress, and UV-C. In this study, we also found that overexpression of PcWRKY11 in A. thaliana could significantly increase salt tolerance. To explore its possible molecular mechanism, further investigations showed that compared with the wild type (WT), under salt stress, the transgenic plants showed a lower malondialdehyde (MDA) content, higher expression of ascorbate peroxidase (APX) and superoxide dismutase (SOD), and higher enzyme activity of peroxidase (POD), superoxide dismutase (SOD), and catalase (CAT). Moreover, the transgenic plants also showed higher expression of Δ1-pyrroline-5-carboxylate synthase (AtP5CS), and higher contents of proline and soluble sugar. Taken together, these results indicate that PcWRKY11 may have a positive role in plants’ adaptation to salinity conditions by reducing reactive oxygen species (ROS) levels and increasing osmosis substance synthesis.

The seed biochemical signature as a potent marker for water logging tolerance in maize

Plant breeders are in the need for convenient, reproducible, reliable and rapid screening methods to be used as a proxy for water logging tolerance for a large number of genotypes. Addressing this need, the present study was carried in order to identify potential biochemical markers in the seeds of 10 contrasting maize (Zea mays L.) genotypes differing in their tolerance against water logging. Results clearly indicate that tolerant genotypes inherently exhibit better antioxidant system as evident by higher activities of catalase and glutathione reductase than the susceptible genotypes hence minimizes resulting oxidative stress. Significantly higher activities of anaerobic metabolism enzymes viz. alcohol dehydrogenase, aldehyde dehydrogenase and pyruvate decarboxylase in tolerant maize genotypes signifies efficient system for the recycling of NADH for the continuation of glycolysis and simultaneous detoxification of acetaldehyde thus provides prolonged survival of tolerant plants under water logging. Higher Sucrose synthase (SuSy) activity in tolerant genotypes over the susceptible genotypes indicates uninterrupted supply of reducing sugars for glycolytic activity. The content of total and reducing sugars content was found 27% higher in tolerant genotypes, which is in agreement with the SuSy activity. Soluble sugars analysis through reverse phase HPLC revealed higher relative concentration of fructose and glucose in tolerant maize genotypes than susceptible genotypes. Tolerant genotypes also exhibited significantly lower phytic acid and higher proline content. Hence the observed biochemical diversity could be useful for screening and development of water logging stress-tolerant genotypes of maize.

The relationship between morpho‐physiological changes and expression of transcription factors in NTT local rice cultivars as a response to drought stress

Response by plants to drought occurs through a series of mechanisms that involve transcription regulation. This research was conducted to study transcription factors (TF) and physiological changes in the drought response of local rice cultivars from East Nusa Tenggara (Nusa Tenggara Timur, NTT) during drought stress. Using three NTT local rice cultivars (Boawae Seratus Malam (BSM), Gogo Jak (GJ), and Kisol Manggarai (KM)) and the fraction of transpirable soil water (FTSW) method with two treatment levels, FTSW 1 (control) and FTSW 0.2 (severe stress), we analyzed the TF expression of OsDREB1A, OsDREB2A, OsWRKY45, and OsNAC6. Based on the result, the highest level of TF expression occurred in the BSM, followed by the GJ and KM cultivars. Analysis of physiological characteristics showed an association between TF expression levels and physiological response, with the BSM cultivar showing high pigment levels, high proline content, and lower H2O2 levels. A linkage was also found in relation to water conservation, as indicated by the higher relative water content and cell membrane stability index in the BSM cultivar in contrast to lower electronic leakage and malondialdehyde percentage when exposed to drought. Based on the results, it can be concluded that the BSM cultivar can be considered as a drought‐tolerant local cultivar according to morpho‐physiological analysis. In this study, all NTT local rice cultivars showed a subtle upregulation of stress‐responsive transcription factors OsDREB1A, OsDREB2A, OsWRKY45, and OsNAC6 as responses to drought stress.

Alternate gene expression profiling of monoterpenes in Hymenocrater longiflorus as a novel pharmaceutical plant under water deficit

Hymenocrater longiflorus (surahalala) is a wild plant species with potential pharmaceutical and ornamental interest. To date, the genomics of this plant is unknown and the gene expression profiling of the genes related to its metabolite has never been studied before. In order to study the responses of in vitro-grown surahalala plants to abiotic stresses and the differential expression of the genes related to its essential oils under exogenous proline application; three levels of PEG600 (0, 10, and 20%) and five levels of proline (0, 5, 10, 15, and 20 µm) were combined in the culture media. Thus, water deficit increased oxidants levels and decreased fresh weight of surahalala tissues, whereas addition of proline up to 15 µm was able to relatively compensate the negative effect of water deficit. Contrarily, high proline level (20 µm) had a negative effect on surahalala plants probably due to the stress simulation (nutrition) under high proline concentration. In addition, the best combination for achieving highest essential oils content was 10 µm proline plus 10% PEG. The expressional profiling of the genes TPS27, L3H, TPS2, TPS1, OMT and GDH3 were successfully carried out and their involvement in 1,8-cineole, carvone, α-pinene, thymol, estragole and β-Citronellol biosynthesis, respectively, was verified. In addition, our results indicated that these genes could also be involved in the synthesis of other metabolites under water deficit condition.

Ecophysiological Responses of Five Mangrove Species (Bruguiera gymnorrhiza, Rhizophora stylosa, Aegiceras corniculatum, Avicennia marina, and Kandelia obovata) to Chilling Stress

Although the low temperature is a critical growth constraint on plants, the physiological mechanism remains unclear, especially in mangrove plants. Hence, the morphological characteristics of five mangrove plants (Bruguiera gymnorrhiza, Rhizophora stylosa, Aegiceras corniculatum, Avicennia marina, and Kandelia obovata) were compared under chilling stress. The contents of hydrogen peroxide (H2O2), malondialdehyde (MDA), and proline were tested. Activities of reactive oxygen species (ROS)-scavenging enzyme [superoxide dismutase (SOD), peroxidase (POD), and catalase (CAT)] were also measured after chilling stress. It was concluded that K. obovata can well tolerate chilling stress, and B. gymnorrhiza suffered the most severe chilling damage. Leaf-morphology observation exhibited that K. obovata and A. corniculatum can sustain chilling stress, while B. gymnorrhiza wilted and A. marina turned brown. The content of H2O2 increased at first and subsequently decreased in all plants. MDA increased instantaneously in B. gymnorrhiza and R. stylosa but changed slowly in K. obovata and A. corniculatum. The high content of proline accumulated in B. gymnorrhiza and K. obovata. The activities of the SOD, POD, and CAT increased at first and then decreased in all mangrove species. The antioxidants maintained high activity in K. obovata while decreasing earliest in A. marina exposed to the long-term chilling stress. Principal component analysis (PCA) indicated that high antioxidant enzyme activities play key roles in chilling tolerance for mangrove plants. The longer-term chilling tolerance of K. obovata may be related to the high antioxidant enzyme activities and proline accumulation. Lower H2O2 and MDA contents strengthen the anti-chilling ability of A. corniculatum. Further investigation on the molecular mechanisms will facilitate the understanding of the anti-chilling ability of mangrove plants.

Molecular and neuronal mechanisms for amino acid taste perception in the Drosophila labellum

Amino acids are essential nutrients that act as building blocks for protein synthesis. Recent studies in Drosophila have demonstrated that glycine, phenylalanine, and threonine elicit attraction, whereas tryptophan elicits aversion at ecologically relevant concentrations. Here, we demonstrated that eight amino acids, including arginine, glycine, alanine, serine, phenylalanine, threonine, cysteine, and proline, differentially stimulate feeding behavior by activating sweet-sensing gustatory receptor neurons (GRNs) in L-type and S-type sensilla. In turn, this process is mediated by three GRs (GR5a, GR61a, and GR64f), as well as two broadly required ionotropic receptors (IRs), IR25a and IR76b. However, GR5a, GR61a, and GR64f are only required for sensing amino acids in the sweet-sensing GRNs of L-type sensilla. This suggests that amino acid sensing in different type sensilla occurs through dual mechanisms. Furthermore, our findings indicated that ecologically relevant high concentrations of arginine, lysine, proline, valine, tryptophan, isoleucine, and leucine elicit aversive responses via bitter-sensing GRNs, which are mediated by three IRs (IR25a, IR51b, and IR76b). More importantly, our results demonstrate that arginine, lysine, and proline induce biphasic responses in a concentration-dependent manner. Therefore, amino acid detection in Drosophila occurs through two classes of receptors that activate two sets of sensory neurons in physiologically distinct pathways, which ultimately mediates attraction or aversion behaviors.

Two Aquaporin Genes, GhPIP2;7 and GhTIP2;1, Positively Regulate the Tolerance of Upland Cotton to Salt and Osmotic Stresses.

Aquaporins (AQPs) facilitate the transport of water and small molecules across intrinsic membranes and play a critical role in abiotic stresses. In this study, 111, 54, and 56 candidate AQP genes were identified in Gossypium hirsutum (AD1), Gossypium arboreum (A2), and Gossypium raimondii (D5), respectively, and were further classified into five subfamilies, namely, plasma intrinsic protein (PIP), tonoplast intrinsic protein (TIP), nodulin 26-like intrinsic protein (NIP), small basic intrinsic protein (SIP), and uncategorized X intrinsic protein (XIP). Transcriptome analysis and quantitative real-time PCR (qRT-PCR) revealed some high-expression GhPIPs and GhTIPs (PIP and TIP genes in G. hirsutum, respectively) in drought and salt stresses. GhPIP2;7-silenced plants decreased in the chlorophyll content, superoxide dismutase (SOD) activity, and peroxidase (POD) activity comparing the mock control (empty-vector) under 400 mM NaCl treatment, which indicated a positive regulatory role of GhPIP2;7 in salt tolerance of cotton. The GhTIP2;1-silenced cotton plants were more sensitive to osmotic stress. GhTIP2;1-overexpressed plants exhibited less accumulation of H2O2 and malondialdehyde but higher proline content under osmotic stress. In summary, our study elucidates the positive regulatory roles of two GhAQPs (GhPIP2;7 and GhTIP2;1) in salt and osmotic stress responses, respectively, and provides a new gene resource for future research.

Impacts of heavy metal, high temperature, and UV radiation exposures on Bellis perennis L. (common daisy): Comparison of phenolic constituents and antioxidant potential (enzymatic and non-enzymatic)

Bellis perennis L., common daisy, is a beneficial medicinal plant used in folk medicine to treat skin diseases, wounds, sore throats, common colds, inflammation, and rheumatism. The objective of this study was to determine the effect of 4 different abiotic stress applications [mercury chloride (HgCl2), copper sulfate (CuSO4), high temperature (45 °C) and ultraviolet radiation (UV)] on individual phenolic constituents, non-enzymatic antioxidant activities (free radical scavenging activity, total phenol-flavonoid content, and proline level), and enzymatic antioxidant activities [superoxide dismutase (SOD) and catalases (CAT)] in common daisy callus cultures. Quantification of the 21 phenolic substances was performed using LC-ESI-MS/MS analysis and all applied stress applications increased specific phenolic constituents comparing with control (no exposure to any stress). Heavy metal stresses (HgCl2 and CuSO4) and high temperature application enhanced the quantity of the selected phenolic substances more than UV-radiation stress. The most noticeable increased quantities were observed with high temperature stress in p-coumaric acid (51.74-fold), and with CuSO4 stress in luteolin (17.76-fold) and apigenin (15.62-fold). Chlorogenic acid was the most prevalent phenolic compound in all tested callus extract including control. Although the first highest total phenol content was obtained with HgCl2 exposure and then followed by high temperature stress, the first highest total flavonoid content was obtained with high temperature stress and then UV radiation. The antioxidant capacity was significantly enhanced (2.11 fold increase) with CuSO4 stress application. Stress-related enzymatic antioxidant activity (SOD and CAT) was elevated the most with HgCl2 stress. Similarly, the highest proline content was obtained with HgCl2 treatment. These findings showed the ability of the phenolic compounds to protect common daisy against harmful heavy metals, high temperature and UV-radiation stresses. The adaptation of the callus under abiotic stress conditions developed here may be useful for the production of optimized phenolic compounds of common daisy and the exploitation of other medicinal species of interest.

Pepper bHLH transcription factor CabHLH035 contributes to salt tolerance by modulating ion homeostasis and proline biosynthesis.

Members of the bHLH family of transcription factors play important roles in multiple aspects of plant biological processes, for instance, abiotic stress responses. Previously, we characterized CaNAC035, a gene that positively regulates stress tolerance and identified CabHLH035, a CaNAC035-interacting protein in pepper (Capsicum annuum L.). In this study, we describe the role of CabHLH035 in the response to salt stress. Our results show that the expression of CabHLH035 increased following salt treatment. Transient expression of CabHLH035 (CabHLH035-To) in pepper enhanced salt tolerance, ectopic expression of CabHLH035 in Arabidopsis increased the salt stress tolerance, whereas knocking down the expression of CabHLH035 in pepper plants resulted in decreased salt tolerance. Homologs of the Salt Overly Sensitive 1 (SOS1) and pyrroline-5-carboxylate acid synthetase (P5CS) genes showed drastically increased expression in transgenic Arabidopsis plants expressing CabHLH035 and CabHLH035-To plants, but expression decreased in CabHLH035-silenced plants. Our results also showed that CabHLH035 can directly bind to the CaSOS1 and CaP5CS gene promoters and positively activate their expression. We found that transgenic Arabidopsis plants, ectopic expression of CabHLH035 and pepper plants transiently overexpressing CabHLH035 (CabHLH035-To) showed lower Na+ and higher proline contents in response to NaCl treatment, while CabHLH035-silenced plants had higher Na+ and lower proline concentrations. Overall, CabHLH035 plays important roles in salt tolerance through its effects on the intracellular Na+ :K+ ratio and proline biosynthesis.

EFFECT OF PEG-INDUCED DROUGHT STRESS ON MUNGBEAN PLANTS REVEALED RESISTANT VARIETIES BASED ON LEAF WILTING INDEX AND BIOCHEMICAL MOLECULES

At the early vegetative growth stage, mungbean are mostly affected by drought, and it is also one of the most promising stages that can be used to screen for drought stress tolerance traits in multiple varieties. Therefore, this study utilized polyethylene glycol (PEG-6000) to induce drought stress towards selection of drought tolerance mungbean varieties in their early vegetative growth stage using both hydroponics and soil based systems. In this study, leaf wilting index and responses of biochemical molecules were used as the basic factors to determine the effect of PEG-induced drought stress among the mungbean varieties. Prior to the imposition of drought stress, germination potentials of the varieties were evaluated and all had germination = 60%. Except for Tvr29 and Tvr44, hydroponic system revealed that = 80% of the varieties had = 1 of their leaves significantly (P = 0.05) wilted. The highest LWI were recorded for Tvr49 and Tvr79. Re-evaluation of Tvr29, Tvr44, Tvr49 and Tvr79 using soil, shows that Tvr29 and TVr44 resisted drought stress. The hydrogen peroxide, superoxide radical and malondialdehyde contents decreased in TVr29 and Tvr44, and increased in Tvr49 and Tvr79 in comparison to the control. Tvr29 and Tvr44 had high proline content than Tvr49 and Tvr79. Based on LWI and biochemical molecules, this study revealed that Tvr29 and Tvr44 should be utilized where water deficit is a challenge to mungbean globally.

Breeding Enrichment of Genetic Variation of Grain Yield and Its Attributes in Bread Wheat under Drought Stress and Well Irrigation

Drought stress (DS) is one of the most critical environmental abiotic stresses for wheat production in the arid environments. Selection of high-yielding genotypes tolerant to DS can play a significant role in mitigation the negative impacts associated with DS. In the present study, generation means analysis (GMA) was used to study the performance of two crosses under well irrigation (WI) and deficit irrigation [cross I (Line 44 × Shandweel-1) and cross II (Line 20 × Sakha 93)]. Significant differences were observed for days to heading (DH), days to maturity (DM), plant height (PH), spike length (SL), number of spikes per plant (NS/P), number of grains per spike (NG/S), thousand-grain weight (TGW), grain yield per plant (GY/P), and proline content (PC) in the six populations of the two crosses within each irrigation level. Cross II had early maturity and the highest PC, NS/P, TGW, and GY/P regardless of the irrigation level. Cross I showed positive significant relative heterosis and heterobeltiosis for GY/P under the two irrigation levels. The inheritance of characters of cross I revealed additive, dominant, and epistatic effects, which varied with trait and stress. Additive genetic effects predominated in DH, SL, and PC, while non- additive were found in DM, NS/P, NG/S, and GY/P. Narrow-sense heritability estimates (h2n) were high for DH and PC, moderate to high for PH and SL, moderate for DM, NG/S, NS/P, and TGW, and low for GY/P. Based on different drought indices the populations BC1, BC2, F1, and P1 of cross II and BC1 of cross I were more tolerant to drought stress. Therefore, PC, TGW and DH can be used as selection indicators to improve wheat for drought tolerance in early generations and other yield components traits in late generations. The second cross (Line 20 × Sakha 93) shows promise and is of interest to a drought tolerance breeding program, where wheat breeders can use recombinant breeding strategies to construct desirable drought stress genes. Correlation and path coefficient revealed that TGW and PC were the main contributor in grain yield in both environments.

Physiological Response of Different Cucumber Hybrid Combinations to Inoculation of Powdery Mildew

In order to study the physiological changes of different cucumber combinations in South China to powdery mildew, on the 0, 1, 3, 6 and 9 days after inoculation of powdery mildew, the changes of disease index, chlorophyll content, defense enzyme activity and osmoregulation substance content of 5 South China hybrid combinations were studied, and relationship between the changes of physiological indexes and the resistance of cucumber powdery mildew was analyzed. The results showed that, according to the disease index, the resistance of 5 cucumber combinations was graded, 18C-3 was disease resistance, 18C-2 and 18C-4 were medium resistance, 18C-1 and 18C-5 were susceptible; after inoculation of 5 cucumber combinations with powdery mildew, the content of chlorophyll decreased, and the content of chlorophyll in 18C-3 was higher than that in other combinations; The activity of superoxide dismutase (SOD), peroxidation(POD) and phenylalanine ammonia lyase (PAL) of most combinations decreased first, and then increased. the activity of polyphenol oxidase (PPO) was up – down – up again. The activity of defense enzyme of resistant combination 18C-3 was significantly higher than that of other combinations, and maintained high proline (PRO) content and low malondialdehyde (MDA) content all the time, indicating that the resistant combination had stronger defense ability and resistance to membrane lipid peroxidation than the susceptible combinations. By analyzing the changes of physiological indexes and the relationship with resistance to powdery mildew of cucumber, the resistant combination of South China type was selected, which provided more theoretical basis for resistance identification and genetic breeding of cucumber powdery mildew.

Advancing knowledge about restricted irrigation strategies on commercial peach plantation under Mediterranean condition

This study was conducted to investigate the effects of different restricted irrigation strategies on peach trees. Sustainable and regulated deficit irrigation treatments were applied during the 2018/2019 production season in a commercial plot of “Bénédicte” variety located at the Atlas Mountain’s region of Morocco. Five different treatments were tested: T1, T2 and T3 with an application of respectively 125% (over-irrigation), 100% (control) and 75% (deficit-irrigation) of Crop Water Requirement (CWR) throughout the whole crop cycle; These treatments were classified under Sustainable Deficit Irrigation treatments (SDI). Regulated Deficit Irrigation treatments (RDI) comprising of treatments T4, and T5 which correspond respectively to applications of 75% ETc and 50% ETc during the pit hardening stage (PH), and 100% ETc during the rest of the cycle. The results showed that deficient irrigation treatments had no effect on vegetative growth parameters.A downward trend in average fruit weight and size at harvest was observed in the T3 treatment. A significant increase in sugar content was observed in T3 and T5 compared to the control T2. With regard to biochemical parameters, the deficient treatment (T5) recorded the highest proline content in response to water stress, followed by T3 and T4. Therewas no significant difference between the crop yields under SDI and RDI treatments, but T4 produced arelatively higher yield of 47 T/Haamong the treatments.Thisled to the water use efficiency (WUE) performance ranking: T3 with 10.63 kg/m3, T4 (75% PH) was in second place with a WUE of 9.6 kg/m3, finally T5 with an efficiency of 9.35 kg/m3.

Role of Exogenous Application of Alpha-Tocopherol in Reducing Low Temperature Stress in Bell Pepper

Changing climatic conditions have an impact on the commercial harvest and production of Capsicum annuum L. across the world. It is a summer crop that grows best at 21°C (low) to 37 °C (high) temperature. Changes in normal growth, poor shoot and root length, increased antioxidant activity, low sugar content, high proline content, and poor yield were observed in bell pepper at low temperature stress. A research trial was conducted on bell peppers in the Department of Plant Pathology at University of Agriculture, Faisalabad. Bell peppers were cultivated hydroponically and alpha-tocopherol control (0ppm), 25ppm, 50ppm, and 100ppm were applied in foliar application. At the reproductive period, a low temperature stress of 18 °C day and 15 °C night was used given. After seven days of foliar spray, plants were exposed to cold temperatures during the day and night. After seven days of stress, the plants were harvested and morphological, physiological, and biochemical data were examined. Plant growth, leaf area, number of leaves, buds, and flowers, photosynthetic pigments, relative water content, cell membrane permeability, total soluble sugar, total reducing sugar, protein contents, and total free amino acid levels were all reduced when exposed to high temperatures. When the stress of low temperature was applied, there was a rise in proline, phenolic, flavonoid, H2O2, MDA, enzymatic antioxidants SOD, CAT, POD, and in APX. Under temperature stress, foliar application of alpha-tocopherol significantly improved CAT, POD, APX activity, decreased MDA, H2O2, and improved proline content. Exogenously administered alpha-tocopherol was found to be effective in boosting capsicum growth and antioxidant capability under low temperature stress.

The Effect of the Application of Stimulants on the Photosynthetic Apparatus and the Yield of Winter Wheat

The use of stimulation preparations seems to be a promising means for mitigating the effects of abiotic and biotic stressors. Their significance includes plant organism stimulation and metabolism optimisation, water regime, and nutrition during periods of stress. They help bridge it over and create conditions for rapid regeneration. In a field experiment, the effect of the application of stimulation preparations on cultivars Triticum aestivum L. with different genetic composition was evaluated (donor of blue aleurone colour KM-72-18; donor of a multi-row spike (MRS) KM-94-18). Our results show a predominantly positive effect of the application of stimulants on the yield and thousand-grain weight (TKW). The results obtained were influenced by the year, based on different temperatures and precipitation. Higher yields were achieved in 2020 with higher total precipitation during the grain filling period and with a higher maximum quantum yield of the photosystem II (Fv/Fm). In 2019, this period was significantly dry and warm, which was reflected in a lower yield and TKM, higher proline content in the leaves, and lower Fv/Fm values. In both experimental years, there was a higher yield of the cultivar with blue aleurone (KM-72-18). In the case of cultivars with coloured grains, the promising use of the content substances in cultivars as natural means of increasing resistance to abiotic and biotic stressors seems to be promising.

Effect of Three Water Regimes on the Physiological and Anatomical Structure of Stem and Leaves of Different Citrus Rootstocks with Distinct Degrees of Tolerance to Drought Stress

Citrus is grown globally throughout the subtropics and semi-arid to humid tropics. Abiotic stresses such as soil water deficit negatively affect plant growth, physiology, biochemistry, and anatomy. Herein, we investigated the effect(s) of three water regimes (control, moderate drought, and severe drought) on the physiological and anatomical structure of 10 different citrus rootstocks with different degrees of tolerance to drought stress. Brazilian sour orange and Gadha dahi performed well by avoiding desiccation and maintaining plant growth, plant water status, and biochemical characters, while Rangpur Poona nucellar (C. limonia) and Sunki × bentake were the most sensitive rootstocks at all stress conditions. At severe water stress, the highest root length (24.33 ± 0.58), shoot length (17.00 ± 1.00), root moisture content (57.67 ± 1.53), shoot moisture content (64.59 ± 1.71), and plant water potential (−1.57 ± 0.03) was observed in tolerant genotype, Brazilian sour orange. Likewise, chlorophyll a (2.70 ± 0.06), chlorophyll b (0.87 ± 0.06) and carotenoids (0.69 ± 0.08) were higher in the same genotype. The lowest H2O2 content (77.00 ± 1.00) and highest proline content (0.51 ± 0.06) were also recorded by Brazilian sour orange. The tolerance mechanism of tolerant genotypes was elucidated by modification in anatomical structures. Stem anatomy at severe drought, 27.5% increase in epidermal cell thickness, 25.4% in vascular bundle length, 30.5% in xylem thickness, 27.7% in the phloem cell area, 8% in the pith cell area, and 43.4% in cortical thickness were also observed in tolerant genotypes. Likewise, leaf anatomy showed an increase of 27.9% in epidermal cell thickness, 11.4% in vascular bundle length, 21% in xylem thickness, and 15% in phloem cell area in tolerant genotypes compared with sensitive ones. These modifications in tolerant genotypes enabled them to maintain steady nutrient transport while reducing the risk of embolisms, increasing water-flow resistance, and constant transport of nutrients across.

Comparative de novo transcriptome analysis identifies salinity stress responsive genes and metabolic pathways in sugarcane and its wild relative Erianthus arundinaceus [Retzius] Jeswiet

Erianthus arundinaceus [Retzius] Jeswiet, a wild relative of sugarcane has a high biomass production potential and a reservoir of many genes for superior agronomic traits and tolerance to biotic and abiotic stresses. A comparative physiological, anatomical and root transcriptome analysis were carried out to identify the salt-responsive genes and metabolic pathways associated with salt-tolerant E. arundinaceus genotype IND99-907 and salinity-sensitive sugarcane genotype Co 97010. IND99-907 recorded growth of young leaves, higher proline content, higher relative water content, intact root anatomical structures and lower Na+/K+, Ca2+/K+ and Mg2+/K+ ratio as compared to the sugarcane genotype Co 97010. We have generated four de novo transcriptome assemblies between stressed and control root samples of IND99-907 and Co 97010. A total of 649 and 501 differentially expressed genes (FDR<0.01) were identified from the stressed and control libraries of IND99-907 and Co 97010 respectively. Genes and pathways related to early stress-responsive signal transduction, hormone signalling, cytoskeleton organization, cellular membrane stabilization, plasma membrane-bound calcium and proton transport, sodium extrusion, secondary metabolite biosynthesis, cellular transporters related to plasma membrane-bound trafficking, nucleobase transporter, clathrin-mediated endocytosis were highly enriched in IND99-907. Whereas in Co 97010, genes related to late stress-responsive signal transduction, electron transport system, senescence, protein degradation and programmed cell death, transport-related genes associated with cellular respiration and mitochondrial respiratory chain, vesicular trafficking, nitrate transporter and fewer secondary metabolite biosynthetic genes were highly enriched. A total of 27 pathways, 24 biological processes, three molecular functions and one cellular component were significantly enriched (FDR≤ 0.05) in IND99-907 as compared to 20 pathways, two biological processes without any significant molecular function and cellular components in Co 97010, indicates the unique and distinct expression pattern of genes and metabolic pathways in both genotypes. The genomic resources developed from this study is useful for sugarcane crop improvement through development of genic SSR markers and genetic engineering approaches.

A PIP-mediated osmotic stress signaling cascade plays a positive role in the salt tolerance of sugarcane

BackgroundPlasma membrane intrinsic proteins (PIPs) are plant channel proteins involved in water deficit and salinity tolerance. PIPs play a major role in plant cell water balance and responses to salt stress. Although sugarcane is prone to high salt stress, there is no report on PIPs in sugarcane.ResultsIn the present study, eight PIP family genes, termed ScPIP1–1, ScPIP1–2, ScPIP1–3, ScPIP1–4, ScPIP2–1, ScPIP2–2, ScPIP2–4 and ScPIP2–5, were obtained based on the sugarcane transcriptome database. Then, ScPIP2–1 in sugarcane was cloned and characterized. Confocal microscopy observation indicated that ScPIP2–1 was located in the plasma membrane and cytoplasm. A yeast two-hybridization experiment revealed that ScPIP2–1 does not have transcriptional activity. Real time quantitative PCR (RT-qPCR) analysis showed that ScPIP2–1 was mainly expressed in the leaf, root and bud, and its expression levels in both below- and aboveground tissues of ROC22 were up-regulated by abscisic acid (ABA), polyethylene glycol (PEG) 6000 and sodium chloride (NaCl) stresses. The chlorophyll content and ion leakage measurement suggested that ScPIP2–1 played a significant role in salt stress resistance in Nicotiana benthamiana through the transient expression test. Overexpression of ScPIP2–1 in Arabidopsis thaliana proved that this gene enhanced the salt tolerance of transgenic plants at the phenotypic (healthier state, more stable relative water content and longer root length), physiologic (more stable ion leakage, lower malondialdehyde content, higher proline content and superoxide dismutase activity) and molecular levels (higher expression levels of AtKIN2, AtP5CS1, AtP5CS2, AtDREB2, AtRD29A, AtNHX1, AtSOS1 and AtHKT1 genes and a lower expression level of the AtTRX5 gene).ConclusionsThis study revealed that the ScPIP2–1-mediated osmotic stress signaling cascade played a positive role in plant response to salt stress.