Increased Proline Content Research Articles

Prevention of drought damage through zeolite treatments onVitis vinifera: A promising sustainable solution for soil management

AbstractViticultural activity is intrinsically interlocked with climatic fluctuations and awful subjected to soil management. Increasing temperatures and reduced precipitation originate several alterations in the metabolic plant pathway and a depletion in grapes quality. The main aspiration of soil management is to keep and retain a microenvironment that considers all vine requirements to upgrade the balance between vegetative growth and cluster quality intensifying its resilience towards abiotic stress. Aiming to establish match and dissimilar drought stress responses among Sangiovese grapevines, we scouted ecophysiological and biochemical alterations after zeolite and irrigation soil application (combined and/or alone), using as control plants naturally exposed to abiotic stress in a Chianti Classico vineyard. When grapevines were exposed to water stress alone, the main reactions encompassed dwindled leaf midday water potential (Ψleaf) and increased proline content. These were accompanied by augments in zeaxanthin and lutein leaf contents, symptomatic of oxidative stress. Positive metabolic alterations in grapes triggered by zeolite and/or water showed some influence on the ripening of the berry differently depending on the year. They created a situation of resilience in berry avoiding arrest in the anthocyanin synthesis pathway during the warmest season and produced a more balanced maturation, closer to the objectives of the modern producer of classic Chianti (i.e. fresher and less alcoholic wines) during the fresher one. Under severe drought, it was activated the shikimic acid pathway and in stressed vines treatment, (WS) a reduction in malic acid content was found. Sugar and phenolic compounds were enhanced by zeolitic and undrought treatments. A negative effect enkindled by the drought and high temperatures combined with stress was the accumulation of quercetin‐3‐O‐rutinoside (Qrut), quercetin‐3‐O‐galactoside (Qgala), quercetin‐3‐O‐glucoside (Qgluc) and quercetin‐3‐O‐glucoronide (Qgluco) in WS treatment. These results summarize that clinoptilolite applied to the soil, both combined with water as well in purity, noteworthy protectorship from more detrimental repercussions of drought‐stressed grapevines, suggesting that new sustainable approaches in soil management are useful for the wellness of vines.

Foliar spraying of exogenous uniconazole (S3307) at the flowering stage as an effective method to resist low-temperature stress on mung bean [Vigna radiata (L.) Wilczek

Low temperature is one of the major constraints on agricultural productivity worldwide and is likely to further increase. Several adaptations and mitigation strategies are required to cope with low-temperature stress. Uniconazole (S3307) could play a significant role in the alleviation of abiotic stress in plants. In this study, the effects of S3307 on the reactive oxygen species (ROS) and antioxidant metabolism were studied in the leaves of mung bean [Vigna radiata (L.) Wilczek]. The experimental results showed that the low-temperature induced accumulation of superoxide anion (O2-) production rate, and malonaldehyde (MDA) contents. Increased proline content and enzymatic antioxidants, including superoxide dismutase (SOD), catalase (CAT), and peroxidase (POD), were found to alleviate oxidative damage under low temperatures. While, S3307 could reduce O2- production rate and MDA contents and increase the activities of SOD, POD, and CAT, slowed the decrease in ascorbic acid (AsA), dehydroascorbic acid (DHA), glutathione (GSH), and oxidized glutathione (GSSG), and promoted increase in soluble sugars (SS), soluble proteins (SP), and proline (Pro) content under low-temperature. At the same time, low temperature leads to lower 100 grain weight and number of grains per plant, which eventually causes yield reduction decreased. Foliar spraying of S3307 could alleviate the yield loss caused by low temperature, and the increase of S3307 treatment was 5.1%–12.5% and 6.3%–32.9% for the two varieties, respectively, compared with CK. In summary, exogenous S3307 pretreatment enhances plant tolerance to low-temperature by improving the antioxidant enzyme activities, increased non-enzymatic antioxidants content, and decreased O2- production rate and MDA contents and inducing alterations in endogenous S3307, and reduce the decrease in mung bean yield.

Response of the antioxidant system of wheat seedlings with different genotypes to exogenous prooxidants: the relationship with resistance to abiotic stressors

Oxidative stress is an important component of heat- and drought-induced damage in plants. However­, information on the relationship between the resistance of cultivated plants with different genotypes to environmental factors and their ability to maintain a pro-/antioxidant balance remains contradictory. This study aimed to compare the growth responses and adaptation ability of the antioxidant system in different wheat cultivars to oxidative stress agents hydrogen peroxide and iron(II) sulfate. Etiolated seedlings of common winter wheat (Triticum aestivum L.) Antonivka and Tobak (heat- and drought-tolerant), and Avgustina and Doskonala (not resistant to heat and drought) were used for the study. Three-day-old etiolated seedlings were exposed to 50 mM H2O2 or 5 mM FeSO4 for one day. It was found that seedlings of Antonivka and Tobak cultivars treated with H2O2 or FeSO4 were able to maintain relatively intensive growth, accumulated significantly lower amounts of endogenous hydrogen peroxide and lipid peroxidation products, significantly increased anthocyanin content and had a higher activity of SOD and catalase as compared with non-resistant cultivars. The non-tolerant cultivars’ response to stress agents was only to increase proline content with a simultaneous decrease in SOD activity and anthocyanins content. The identified varietal markers of the antioxidant system adaptive strategy can be used to develop new approaches for screening wheat cultivars with cross-resistance to major abiotic stressors. Keywords: antioxidant system, drought resistan­ce, ferrous sulphate, H2O2, heat tolerance, oxidative stress, Triticum aestivum seedlings

Dynamic physiological and transcriptomic changes reveal memory effects of salt stress in maize

BackgroundPre-exposing plants to abiotic stresses can induce stress memory, which is crucial for adapting to subsequent stress exposure. Although numerous genes involved in salt stress response have been identified, the understanding of memory responses to salt stress remains limited.ResultsIn this study, we conducted physiological and transcriptional assays on maize plants subjected to recurrent salt stress to characterize salt stress memory. During the second exposure to salt stress, the plants exhibited enhanced salt resistance, as evidenced by increased proline content and higher POD and SOD activity, along with decreased MDA content, indicative of physiological memory behavior. Transcriptional analysis revealed fewer differentially expressed genes and variations in response processes during the second exposure compared to the first, indicative of transcriptional memory behavior. A total of 2,213 salt stress memory genes (SMGs) were identified and categorized into four response patterns. The most prominent group of SMGs consisted of genes with elevated expression during the first exposure to salt stress but reduced expression after recurrent exposure to salt stress, or vice versa ([+ / −] or [− / +]), indicating that a revised response is a crucial process in plant stress memory. Furthermore, nine transcription factors (TFs) (WRKY40, WRKY46, WRKY53, WRKY18, WRKY33, WRKY70, MYB15, KNAT7, and WRKY54) were identified as crucial factors related to salt stress memory. These TFs regulate over 53% of SMGs, underscoring their potential significance in salt stress memory.ConclusionsOur study demonstrates that maize can develop salt stress memory, and the genes identified here will aid in the genetic improvement of maize and other crops.

Low-temperature perception and modulations in Ocimum basilicum commercial cultivar CIM-Shishir: Biosynthetic potential with insight towards climate-smart resilience

The newly released interspecific hybrid variety CIM-Shishir, resulting from a cross between Ocimum basilicum and Ocimum kilimandscharicum claims to be a multicut, lodging resistant, cold tolerant, high essential oil yielding with linalool rich variety. It has a purple-green stem and has a unique feature and advantage of better survival in the winter season than other O. basilicum varieties, illustrating its physiological mechanisms for cold tolerance. In this study, we subjected both the CIM-Shishir variety and a control plant to cold stress to investigate the impact of low temperatures on various physiological, trichome developments, secondary metabolite constitution aspects related to essential oil production, and gene expression. The analysis revealed a significantly higher density and altered morphology of trichomes on the leaf surface of the variety subjected to low temperatures, indicating its adaptation to cold conditions. Furthermore, when comparing the treated plants under low-temperature stress, it was observed that the relative electrolyte leakage and Malondialdehyde (MDA) contents substantially increased in the control in contrast to the CIM-Shishir variety. This finding suggests that CIM-Shishir exhibits superior cold tolerance. Additionally, an increase in proline content was noted in the variety exposed to low temperatures compared to the control. Moreover, the chlorophyll and anthocyanin content gradually increased with prolonged exposure to low-temperature stress in the newly developed variety, indicating its ability to maintain photosynthetic capacity and adapt to cold conditions. The activities of superoxide dismutase (SOD) also increased under low-temperature conditions in the CIM-Shishir variety, further highlighting its cold tolerance behaviour. In our research, we investigated the comprehensive molecular mechanisms of cold response in Ocimum. We analyzed the expression of key genes associated with cold tolerance in two plant groups: the newly developed hybrid variety known as CIM-Shishir Ocimum, which exhibits cold tolerance, and the control plants susceptible to cold climates that include WRKY53, ICE1, HOS1, COR47, LOS15, DREB5, CBF4, LTI6, KIN, and ERD2. These genes exhibited significantly higher expression levels in the CIM-Shishir variety compared to the control, shedding light on the genetic basis of its cold tolerance. The need for climate-smart, resilient high-yielding genotype is of high importance due to varied climatic conditions as this will hit the yield drastically and further to the economic sectors including farmers and many industries that are dependent on the bioactive constituents of Ocimum.

Comparative field studies of biochemical and agro-physiological parameters in semi-arid zone with rainfall Moroccan climate of durum wheat

Durum wheat production is highly unpredictable throughout the year because of uncertain rainfall and frequent dry spells and it is absolutely necessary to characterize the impact of drought on grain yield. The objective in this research is to carry out a comparative analysis of biochemical and physiological responses and production parameters of durum wheat (Triticum durum) in semi-arid zone with rainfall in Morocco's climates. Thirteen durum wheat genotypes selected at INRA-Morocco and three control varieties were evaluated under Moroccan rainfed conditions for two growing seasons (2019/20 and 2020/21). The INRA-Morocco-Douyet Fez experimental field site was where the trials were conducted (34°2 N, 5°W, 416 m). Different parameters were studied. Five physiological, four agronomical and one biochemical trait are measured in this study: leaf area, leaf temperature, relative water content, chlorophyll content, proline, yield and yield components. Decreased rainfall significantly increased proline content, leaf temperature and decreased leaf area, grain yield, chlorophyll and relative water content (P < 0.01). Based on these results, field-induced rainfall variations resulted in inconsistencies in the response of the assessed traits to drought-related interactions between both growing seasons (2020–2021) in order to identify stable, high-yielding genotypes in the presence and absence of rainfall, which requires a strong association of drought-related traits.

Nano-silicone and Ascophyllum nodosum-based biostimulant down-regulates the negative effect of in vitro induced-salinity in Rosa damascena

BackgroundRosa damascena is extensively cultivated in various regions of Iran due to its aesthetic attributes, medicinal qualities, and essential oil production. This study investigated the efficacy of Ascophyllum nodosum extract (AnE) at concentrations of 0, 2, and 3 g L− 1 and Nano-silicon (nSiO2) at concentrations of 0, 50, and 100 mg L− 1 in ameliorating the impact of salinity on two genotypes of Damask rose (‘Chaharfasl’ and ‘Kashan’) under in vitro culture conditions. Additionally, various physio-chemical characteristics of R. damascena explants were assessed.ResultsThe findings revealed that exposure to 100 mM NaCl resulted in a substantial reduction in the Relative Water Content (RWC), Membrane Stability Index (MSI), leaf pigments (Chlorophyll b, Chlorophyll a, total Chlorophyll, and carotenoids), chlorophyll fluorescence parameters, and protein content in both genotypes when compared to control conditions. Salinity induced a significant increase in the parameter F0 and a decrease in the parameter Fv/Fm compared to the control conditions in both genotypes. Nonetheless, the genotype Kashan treated with 3 g L− 1 AnE + 100 mg L− 1 nSiO2 exhibited the maximum Fm value under control conditions, with a significant difference compared to other treatments. Furthermore, salinity caused a considerable reduction in Fm in both ‘Kashan’ and ‘Chaharfasl’ by 22% and 17%, respectively, when compared to the control condition. ‘Kashan’ displayed the maximum Fv/Fm compared to the other genotype. The maximum levels of Malondialdehyde (MAD) and hydrogen peroxide (H2O2) were also observed in explants affected by salinity. The combination of 3 g L− 1 AnE + 100 mg L− 1 nSiO2, followed by 2 g L− 1 AnE + 100 mg L− 1 nSiO2, exhibited substantial positive effects. Salinity also led to an increase in proline content and the activity of peroxidase (POD), superoxide dismutase (SOD), guaiacol peroxidase (GPX), and catalase (CAT) in both genotypes. The activity of these enzymes was further enhanced when AnE was applied at concentrations of 2 and 3 g L− 1 in combination with 100 mg L− 1 nSiO2.ConclusionsThe ‘Kashan’ genotype displayed greater tolerance to salinity by enhancing water balance, maintaining membrane integrity, and augmenting the activity of antioxidant enzymes compared to ‘Chaharfasl’. The utilization of nSiO2 and AnE biostimulants demonstrated potential benefits for R. damascena, both under salinity and control conditions. These findings hold substantial importance for researchers, policymakers, and farmers, offering valuable insights into the development of salinity-tolerant crop varieties.

Gamma-aminobutyric acid modulates antioxidant and osmoprotective systems in seedlings of Triticum aestivum cultivars differing in drought tolerance

The stress-protective effects of plant neurotransmitters, including gamma-aminobutyric acid (GABA) have been intensively examined in recent years. However, studies on the GABA influence on stress protective systems in bread wheat cultivars with different drought adaptation strategies are still lacking. The aim of this work was to estimate the GABA effect on the state of antioxidant and osmoprotective systems in etiolated seedlings of two wheat cultivars differing significantly in drought tolerance, namely Doskonala (non-drought-resistant) and Tobak (drought-resistant) under model drought induced by PEG 6000. Two-day-old seedlings were transferred to 15% PEG 6000 and incubated for two days in the absence or presence of GABA. Treatment with 0.1 and 0.5 mM GABA significantly reduced the growth-inhibitory effect of PEG 6000 on the roots and shoots of both cultivars, but to a greater extent on those of non-resistant Doskonala. It was shown that GABA treatment reduced drought-induced accumulation of H2O2 and MDA, stabilized SOD and GPX activity, the level of sugars, anthocyanins and flavonoids in seedlings of both cultivars. Meanwhile GABA treatment enhanced the stress-induced increase in proline content in the Doskonala cultivar, but decreased it in the Tobak, completely prevented stress induced decrease in anthocyanins and flavonoids level in the Tobak and only partially in Doskonala cultivar. Thus, the stabilization of the stress-protective systems functioning in the wheat cultivars and variety-dependent differences in response to GABA were revealed. Keywords: anthocyanins, antioxidant system, drought resistance, gamma-aminobutyric acid, oxidative stress, proline, Triticum aestivum

Seed priming with plant growth-promoting rhizobacteria and supplementation of culture medium with biochar alleviated salinity damages in Prosopis koelziana seedlings

The Prosopis koelziana genus, a member of the Fabaceae family, is crucial to the ecology and economy of arid areas. It is commonly used to restore deserts, forests, and degraded soil with low fertility and high salt concentration. However, recent studies found that the seedlings of P. koelziana are highly susceptible to salinity stress despite having a high tolerance to it. To address this issue, an experiment was conducted to determine if plant growth-promoting rhizobacteria (PGPR) pretreatment and biochar application could enhance the seedlings’ tolerance to saline conditions. The research showed that salinity stress decreased seedling growth but increased proline content, soluble sugar content, and antioxidant enzyme activity. Na+ ions increased in plants under salt stress, while K+ ions decreased. The results indicated that the pretreatment of plants with biochar and bacteria increased the fresh weight of seedlings by about 23%, 58%, and 50% in 200, 400, and 600 mM NaCl, respectively, compared with non-pretreated plants. Biochar and bacteria application also increased the proline content by about 62%, 46%, 32%, and 45% in 0, 200, 400, and 600 mM NaCl. This experiment showed that bacteria and biochar pretreatment of plants reduced oxidative stress and sodium uptake (20%, 28%, and 10% decrement of root Na uptake in 200, 400, and 600 mM NaCl). Therefore, these two bio stimulators should be used together for more significant effects on the salinity mitigation of P. Koelziana seedlings and the production of resistant seedlings that have a high ability to transfer to the field.

Comparative efficacy of different salt tolerant rhizobial inoculants in improving growth and productivity of Vigna radiata L. under salt stress

Worldwide, salinity severely affects agricultural production of crops such as mung bean in arid and semi-arid regions. In saline conditions, various species of Rhizobium can be used to enhance nodulation and induce salinity tolerance in maize. The present study conducted a pot experiment to determine the efficiency of three rhizobial isolates under different salinity conditions, such as 1.41, 4 and 6 dS m−1, on mung bean growth parameters, antioxidant status and yield. Results revealed that salt stress imparted adverse effects on the growth, antioxidants, yield and nodulation of mung bean. Under high salt stress conditions, fresh weights were reduced for roots (78.24%), shoots (64.52%), pods (58.26%) and height (32.33%) as compared to un-inoculated control plants. However, an increase in proline content (46.14%) was observed in high salt stressed plants. Three Rhizobium isolates (Mg1, Mg2, and Mg3), on the other hand, mitigated the negative effects of salt stress after inoculation. However, effects of Mg3 inoculation were prominent at 6 dS m−1 and it enhanced the plant height (45.10%), fresh weight of shoot (58.68%), root (63.64%), pods fresh weight (34.10%), pods number per plant (92.04%), and grain nitrogen concentration (21%) than un-inoculated control. Rhizobium strains Mg1, and Mg2 expressed splendid results at 1.41 and 4 dS m−1 salinity stress. The growth promotion effects might be due to improvement in mineral uptake and ionic balance that minimized the inhibitory effects caused by salinity stress. Thus, inoculating with these strains may boost mung bean growth and yield under salinity stress.

2-hydroxymelatonin (2-OHM), a major melatonin metabolite, confers multiple stress tolerance in pepper at seed germination stage

Besides affecting or regulating several crucial processes in plants’ growth and development, melatonin is also highly effective at reducing the oxidative damage induced by various abiotic stressors and therefore it is regarded as a new master plant hormone. The interaction of melatonin with several oxygenated compounds results in the formation of various metabolites that also exhibit melatonin-like functions. Although 2-hydroxymelatonin (2-OHM) is one of the principal melatonin metabolites found in plants, its possible roles in plant life are yet to be fully revealed. This study investigated the impact of 2-OHM treatment on pepper seed germination and seedling growth under various abiotic stress conditions. Pepper seeds treated with 50 µM 2-OHM were subjected to germination and emergence tests under chilling, salt, and water stress conditions. The results demonstrated that 2-OHM treatment significantly enhanced seed germination and seedling emergence performance compared to untreated seeds under stress conditions. The 2-OHM-treatemant resulted in higher final seed germination (FGP) and seedling emergence percentage (FEP) and root length under chilling and water stress conditions. Exogenously applied 2-OHM also significantly shortened the seed germination and emergence periods under chilling conditions as indicated by higher mean germination (MGT) and emergence rates (MET). Additionally, the 2-OHM treatment improved root length, FEP and MET under salt stress. In general, the 2-OHM treatment effectively reduced malondialdehyde (MDA) and hydrogen peroxide (H2O2) levels while increasing proline content and amplifying the activities of antioxidant enzymes superoxide dismutase (SOD), catalase (CAT) and peroxidase (POX) under all stress conditions. In conclusion, the 2-OHM treatment significantly improved seed germination and seedling performance and enhanced stress resilience in pepper at germination stage. This study highlights the potential of 2-OHM as an effective natural compound to enhance crop productivity and alleviate the adverse effects of abiotic stressors in agricultural practices. Future experiments will also assist in elucidation of 2-OHM intervened stress mitigation procedure in pepper.

28-Homobrassinolide Primed Seed Improved Lead Stress Tolerance in Brassica rapa L. through Modulation of Physio-Biochemical Attributes and Nutrient Uptake.

Brassinosteroids (BRs) influence a variety of physiological reactions and alleviate different biotic and abiotic stressors. Turnip seedlings were grown with the goal of further exploring and expanding their function in plants under abiotic stress, particularly under heavy metal toxicity (lead stress). This study's objective was to ascertain the role of applied 28-homobrassinolide (HBL) in reducing lead (Pb) stress in turnip plants. Turnip seeds treated with 1, 5, and 10 µM HBL and were grown-up in Pb-contaminated soil (300 mg kg-1). Lead accumulation reduces biomass, growth attributes, and various biochemical parameters, as well as increasing proline content. Seed germination, root and shoot growth, and gas exchange characteristics were enhanced via HBL treatment. Furthermore, Pb-stressed seedlings had decreased total soluble protein concentrations, photosynthetic pigments, nutrition, and phenol content. Nonetheless, HBL increased chlorophyll a and chlorophyll b levels in plant, resulting in increased photosynthesis. As a result, seeds treated with HBL2 (5 µM L-1) had higher nutritional contents (Mg+2, Zn+2, Na+2, and K+1). HBL2-treated seedlings had higher DPPH and metal tolerance indexes. This led to the conclusion that HBL2 effectively reduced Pb toxicity and improved resistance in lead-contaminated soil.

Effects of PmaIAA27 and PmaARF15 genes on drought stress tolerance in pinus massoniana

BackgroundAuxin plays an important role in plant resistance to abiotic stress. The modulation of gene expression by Auxin response factors (ARFs) and the inhibition of auxin/indole-3-acetic acid (Aux/IAA) proteins play crucial regulatory roles in plant auxin signal transduction. However, whether the stress resistance of Masson pine (Pinus massoniana), as a representative pioneer species, is related to Aux/IAA and ARF genes has not been thoroughly studied and explored.ResultsThe present study provides preliminary evidence for the regulatory role of the PmaIAA27 gene in abiotic stress response in Masson pine. We investigated the effects of drought and hormone treatments on Masson pine by examining the expression patterns of PmaIAA27 and PmaARF15 genes. Subsequently, we conducted gene cloning, functional testing using transgenic tobacco, and explored gene interactions. Exogenous auxin irrigation significantly downregulated the expression of PmaIAA27 while upregulating PmaARF15 in Masson pine seedlings. Moreover, transgenic tobacco with the PmaIAA27 gene exhibited a significant decrease in auxin content compared to control plants, accompanied by an increase in proline content - a known indicator of plant drought resistance. These findings suggest that overexpression of the PmaIAA27 gene may enhance drought resistance in Masson pine. To further investigate the interaction between PmaIAA27 and PmaARF15 genes, we performed bioinformatics analysis and yeast two-hybrid experiments which revealed interactions between PB1 structural region of PmaARF15 and PmaIAA27.ConclusionThe present study provides new insights into the regulatory functions of Aux/IAA and ARF genes in Masson pine. Overexpression of PmaIAA gene may have negative effects on the growth of Masson pine, but may improve the drought resistance. Therefore, this study has great application prospects.

Growth, Physiology and Nutritional Quality of C4 Halophyte Portulaca oleracea L. Grown Aeroponically in Different Percentages of Artificial Seawater under Different Light-Emitting Diode Spectral Qualities.

Edible halophyte Portulaca oleracea L., known as purslane, was grown in two percentages of artificial seawater (ASW) under two combined red (R) and blue (B) LED spectra. High salinity (40% ASW) negatively affected shoot productivity and leaf growth of purslane compared to those grown in 10% ASW. Photosynthetic pigment and total reduced nitrogen concentrations were significantly higher in purslane grown in 10% ASW than in 40% ASW. However, LED spectral quality did not markedly influence these parameters. Grown in 10% ASW under R/B 2.2, purslane had the highest maximum nitrate reductase activity, while those in 40% ASW under R/B 2.2 had the highest activation state. Under both light qualities, purslane had a sevenfold increase in proline concentration in 40% ASW than in 10% ASW. Total phenolic compounds' concentration was the highest in 10% ASW under R/B 0.9, while there were no significant differences in the accumulation of total soluble sugars and ascorbic acids among all plants. Antioxidant enzymes activities were lower in 40% ASW under R/B 2.2 compared to the other conditions. In conclusion, salinity affected the yield, physiology and nutritional quality of purslane. The impacts of LED spectral quality on purslane were only reflected by certain physiological and nutritional parameters.

The effect of free proline accumulation on the content of photosynthetic pigments in transgenic wheat plants

Aim. To analyze the effect of L-proline accumulation on chlorophyll content in transgenic wheat plants with a double-stranded RNA suppressor of the proline dehydrogenase gene under physiological and stress conditions. Methods. Agrobacterium-mediated transformation in planta; biochemical determination of free proline content; spectrophotometric determination of photosynthetic pigments content; of mathematical statistics. Results. It was shown that the content of free proline in the leaves of transgenic plants under physiological conditions was 1.7-1.9 times higher compared to the original genotype. Under conditions of drought, the content of this aminoacid increased in non-transformed plants of the original genotypes by 2.9-3.1 times, and in transgenic plants – by 4.5-4.9 times. The amount of chlorophyll in the flag leaves of plants of the original genotypes and their transgenic lines under physiological conditions did not differ significantly, while under drought conditions in the first of them it was 1.1-1.2 times less than in the second. Drought reduced the total chlorophyll content in plants of the original genotype to 85-90 %, compared to physiological conditions, while no significant changes were found in transgenic plants. Conclusions. It was established that under conditions of soil drought, the increase in proline content in genetically modified wheat plants compared to non-transgenic ones is accompanied by an increase in the amount of total chlorophyll (by 10-15 %), which indicates a better efficiency of their pigment apparatus under stressful conditions.

Characterization of sandalwood (E,E)-α-farnesene synthase whose overexpression enhances cold tolerance through jasmonic acid biosynthesis and signaling in Arabidopsis.

Santalum album (E,E)-α-farnesene synthase catalyzes FPP into (E,E)-α-farnesene. Overexpression of the SaAFS gene positively improved cold stress tolerance through JA biosynthesis and signaling pathways in Arabidopsis. Volatile terpenoids are released from plants that suffer negative effects following exposure to various biotic and abiotic stresses. Recent studies revealed that (E,E)-α-farnesene synthase (AFS) plays a significant role in a plant's defence against biotic attack. However, little is known about whether AFS contributes to plant resistance to cold stress. In this study, a SaAFS gene was isolated from Indian sandalwood (Santalum album L.) and functionally characterized. The SaAFS protein mainly converts farnesyl diphosphate to (E,E)-α-farnesene. SaAFS was clustered into the AFS clade from angiosperms, suggesting a highly conserved enzyme. SaAFS displayed a significant response to cold stress and methyl jasmonate. SaAFS overexpression (OE) in Arabidopsis enhanced cold tolerance by increasing proline content, reducing malondialdehyde content, electrolyte leakage, and accumulating reactive oxygen species. Transcriptomic analysis revealed that upregulated genes related to stress response and JA biosynthesis and signaling were detected in SaAFS-OE lines compared with wild type plants that were exposed to cold stress. Endogenous JA and jasmonoyl-isoleucine content increased significantly in SaAFS-OE lines exposed to cold stress. Collectively considered, these results suggest that the SaAFS gene is a positive regulator during cold stress tolerance via JA biosynthesis and signaling pathways.

Exploring the synergistic effects of melatonin and salicylic acid in enhancing drought stress tolerance in tomato plants through fine-tuning oxidative-nitrosative processes and methylglyoxal metabolism

Enhancement of drought stress (DS) tolerance in plants has been reported with the separate applications of melatonin (MT) and salicylic acid (SA). However, the synergistic effects of their combined application and the exact mechanisms through which they enhance drought tolerance are still not fully understood. The study explored the joint effects of MT and SA on DS tolerance and their implications for oxide-nitrosative processes and methylglyoxal metabolism in tomato plants. To impose DS in tomato plants, they were treated with a 6% polyethylene glycol solution (PEG-6000) in a half-strength nutrient solution. The plants underwent a treatment consisting of individual or combined spraying with 0.5 mM SA and/or 0.1 mM MT every two days for 14 days to relieve the after effects of the PEG-induced stress. The combined MT and SA treatment improved plant drought tolerance, resulting in significant increases in shoot (75%) and root (204%) dry weights. Other improvements included a 141% increase in total chlorophyll content, a 61% increase in Fv/Fm, a 39% increase in Ψl, a 50% increase in RWC, and a 76% increase in proline content compared to DS alone. It also increased non-enzymatic antioxidants (ascorbate and glutathione) and decreased oxidized glutathione under DS. The combined treatment also led to decreased levels of hydrogen peroxide, carbonyl (-CO), and thiol (-SH) groups, indicating the activation of the oxide-nitrosative system. Additionally, the treatment with MT and SA together increased the activity of l-cysteine desulfhydrase (L-CD), resulting in the production of hydrogen sulfide (H2S) and nitric oxide (NO), while decreasing the activity of S-nitroso glutathione reductase, which may have accelerated S-nitrosylation. The synthesis of methylglyoxal (MG) was also reduced by the combined treatment, possibly through the upregulation of the glyoxalase system. Overall, our study presents evidence that the combination of MT and SA treatment can enhance tomato plant tolerance to DS by regulating the oxidative-nitrosative processes and methylglyoxal metabolism.

Water-Deficit Stress in the Epiphytic Elkhorn Fern: Insight into Photosynthetic Response.

Progressive climate changes cause disturbance of water relations in tropical rainforests, where epiphytic ferns are an important element of biodiversity. In these plants, the efficiency of photosynthesis is closely related to the efficiency of water transport. In addition, due to the lack of contact with the soil, epiphytes are extremely susceptible to water-deficit stress. The aim of this experiment was to determine the response of the photosynthetic apparatus of Platycerium bifurcatum to a 6-week water deficit. The hydration and pigment composition of leaves were determined using reflectance spectroscopy and epifluorescence microscopy. Chlorophyll a fluorescence kinetics parameters, fluorescence induction curves (OJIP), low-temperature fluorescence curves at 77 K and proline concentration were analyzed at seven time points. After a decrease in leaf hydration by 10-15%, there were disturbances in the oxidation-reduction balance, especially in the initial photochemical reactions, a rapid decrease in plant vitality (PI) and significant fluctuations in chlorophyll a fluorescence parameters. The relative size of PSI antenna structures compared to PSII decreased in the following weeks of water deficit. Changes in photochemical reactions were accompanied by a decrease in gross photosynthesis and an increase in proline concentration. Changes in the functioning of photosynthesis light phase and the pigment composition of leaves are related to the resistance of elkhorn fern to long-term water deficit.

Effects of dopamine D2 receptor antagonists on retinal pigment epithelial/choroid complex metabolism in form-deprived myopic guinea pigs.

The retinal pigment epithelial (RPE)/choroid complex regulates myopia development, but the precise pathogenesis of myopia remains unclear. We aimed to investigate the changes in RPE/choroid complex metabolism in a form deprivation myopia model after dopamine D2 receptor (D2R) modulation. Guinea pigs were randomly divided into normal (NC), form deprivation myopia (FDM), and FDM treated with dopamine D2R antagonist groups. Differential metabolites were screened using SIMCA-P software and MetaboAnalyst metabolomics analysis tool. Functions of differential metabolites were analyzed using KEGG enrichment pathways. Relative to the NC group, 38 differential metabolites were identified, comprising 29 increased metabolites (including nicotinic acid, cytosine, and glutamate) and 9 decreased metabolites, of which proline exhibited the largest decrease. Pathway analysis revealed regulation of arginine/proline and aspartate/glutamate metabolism. Intravitreal D2R antagonist injection increased proline concentrations and activated arginine/proline and purine metabolism pathways. In sum, D2R antagonists alleviated the myopia trend of refractive biological parameters in form deprivation myopic guinea pigs, suggesting the involvement of dopamine D2R signaling in myopia pathogenesis. The RPE/choroid may provide glutamate to the retina by activating proline metabolism via metabolic coupling with the retina. Dopamine D2R antagonism may modulate proline/arginine metabolic pathways in the RPE/choroid and regulate metabolism, information presentation, and myopia.

Seed priming with Beauveria bassiana improves growth and salt stress response in rice

One of the most important abiotic factors that hinder plant development, growth, and production is salt stress. In recent years, there has been a lot of interest in the biological treatment of salt stress in plants using beneficial microbes. The fungal endophyte Beauveria bassiana provides a wide variety of ecosystem services, like suppressing insect pests and pathogens and enhancing plant growth. However, the role of B. bassiana in reducing salt stress in plants has not yet been clarified. This study was undertaken to evaluate the performance of B. bassiana isolate BeauA1 primed rice under salt stress by estimating rice growth, stress parameters, and mitigator characteristics. Primarily, rice seeds were primed with BeauA1 and placed in an agar medium with 120 mM NaCl (≈12 dS m−1 salt solution) to observe the role of BeauA1 in the early establishment of rice seedlings in salt conditions. Seed priming with BeauA1 resulted in an enhancement of rice growth attributes under both control and NaCl stress conditions. In the pot experiment, the BeauA1 primed rice seedlings were planted in soil with different concentrations of salt, viz. 8, 10, and 12 dS m−1. The BeauA1 primed rice plants showed improvement in leaf succulence, leaf area, photosynthetic pigments, and shoot relative water content (RWC), leading to enhanced growth under both salt stress and control conditions. The biochemical study found that BeauA1 considerably increased proline content, total soluble sugars, total carbohydrates, and K+/Na+ in leaves. The antioxidant enzymes catalase (CAT), ascorbate peroxidase (APX), peroxidase (POD), glutathione S-transferase (GST), and nonenzymatic antioxidants phenol and flavonoid were upregulated in BeauA1-primed plants under both control and stressed conditions. Further significant reductions of the lipid peroxidation products malondialdehyde (MDA) and hydrogen peroxide (H2O2) by BeauA1 under salt stress were consistent with higher antioxidant activities in salt stress conditions. Principal component analysis (PCA) further validated BeauA1-primed plants' modulation of growth, antioxidant defense, and reduction of MDA and H2O2 in rice under salt-stress conditions. Our findings indicated that utilizing BeauA1 to reduce salt stress would be a useful strategy to increase rice yield in salt-affected regions.