Plant Tolerance Research Articles

Review of Drought Stress and Seed Priming Effects on Upland Rice Yield and Longevity

Unequal plant stand and poor germination are major constraints in seeds under areas which receive erratic and low rainfall. Seed priming has emerged as a crucial strategy to enhance the biochemical, physiological, and ecological resilience of seeds and seedlings. Employing suitable priming methods at different developmental stages can significantly improve drought tolerance in plants. Research indicates that the primary factors leading to seed deterioration are the combined effects of low temperatures and moisture levels, which trigger abnormal biochemical and physiological responses. Seed priming techniques show promise due to their simplicity and adaptability in local agricultural practices. However, one of the challenges associated with primed seeds is their relatively short storage lifespan. This review aims to explore the biochemical, physiological, and molecular aspects of rice seed priming while proposing innovative techniques to extend seed longevity, improve stand establishment, and increase overall yield. Furthermore, understanding the molecular mechanisms underlying seed priming can lead to the development of more effective priming protocols. This could ultimately contribute to sustainable agricultural practices in regions vulnerable to climate variability.

Associations of Arbuscular Mycorrhizal Fungi (AMF) for Enhancements in Soil Fertility and Promotion of Plant Growth: A Review

Arbuscular Mycorrhizal Fungi are used for soil fertility enhancements and stimulating plant growth in which they association with other organisms like terrestrial plants. Mycorrhizas create an association between fungi and the roots of plants. Therefore, the review was made to point out important fungal species involved in fungal plant interaction and their major roles in agriculture as well as ecosystem. 80% of plants form associations with mycorrhizal fungi. The fungal are used to use their different organs like chain, arbuscular, vesicle, supportive cells and spore to interact with the other plant/ plat’s organ. The mycorrhizal fungi can be categorized into two principal classifications based on their anatomical interactions with the roots of host plants. Arbuscular Mycorrhizal and Ectomycorrhizal fungi utilize two distinct strategies for nutrient acquisition. The main categories of vesicular arbuscular mycorrhizal associations are linear or coiling and of ectomycorrhizal associations are epidermal or cortical. The rhizospheric and endophytic microbes promote plant growth as inoculated with crop. AM fungi as an obligate symbiont share a distinct feature called arbuscules as a site of nutrient exchanges between host and fungi. Arbuscules developed between cell wall and plasma membrane of root cortical cells and differentiated from plant plasma membrane by periarbuscular membrane. Arbuscular mycorrhizal fungi (AMF) play an indispensable role in augmenting plant nutrient acquisition, enhancing plant resilience and tolerance to various environmental stresses, improving soil fertility and structure, and providing numerous beneficial effects. AMF engage in interactions with other soil microorganisms, such as plant growth-promoting rhizobacteria, resulting in a synergistic effect that promotes plant growth and offers protection against pathogens associated with Rhizobia. Both AMF and Rhizobia utilize the same signaling pathways, which facilitate their association with host plants and enable nitrogen fixation within the soil ecosystem. A positive relationship has been established between AMF colonization and the diversity of soil microbial communities. Nitrogen-fixing rhizobia, mycorrhizal fungi, and root nodule symbioses typically exhibit synergistic interactions concerning infection rates and their effects on mineral nutrition and plant growth, thereby significantly enhancing the status of soil fertility, particularly with respect to soil quality characteristics.

Choline supplementation reduces cadmium uptake and alleviates cadmium toxicity in Solanum lycopersicum seedlings

Sustainable plant production in soil polluted with heavy metals requires that novel strategies are developed for the benefit of humans and other living things. Cadmium (Cd) is a common heavy metal pollutant for plants, and there is limited information on the use of exogenous bio-regulators to reduce the accumulation and toxic effects of Cd pollution in plants. Choline is an endogenous quertarnary amine that is known to improve stress tolerance in plants, while its mechanism of action in certain conditions is yet to be determined. This study investigated the effects of foliar choline supplementation (10 mM) on Solanum lycopersicum seedlings exposed to Cd application (50 mg/L in soil). The seedlings were randomized to five groups: Control (E1), Cd stress (E2), Choline supplementation after Cd stress (E3), Choline (E4), and Choline supplementation before Cd stress (E5). Following the applications, the Cd content, growth and development parameters (chlorophyll content, fresh and dry weight), oxidative stress parameters (H2O2 and MDA contents), as well as antioxidative defense system (SOD, GSH, AsA, and TPC contents) were analyzed. Choline supplementation after Cd stress reduced the enhanced Cd content in roots by 38% but did not alter it in leaves (p > 0.05) compared to the Cd group. Choline supplementation before Cd stress decreased Cd content both in roots by 87.5% and in leaves by 50%. Choline supplementation after and before Cd stress increased fresh and dry weights in both roots and leaves. While the Cd group (E2) increased the H2O2 level and SOD activity, no remarkable change was observed in H2O2 levels in all choline supplementations (E3, E4, E5). Therefore, lipid peroxidation (MDA) was not observed in choline supplementation before Cd stress (E5), however, when the choline was applied after Cd stress (E3) MDA content was reduced by 40% compared with the Cd stress group (E2). Choline supplementations after and before Cd stress (E3, E5) increased AsA content by 30%, while the Cd group (E2) decreased it by 60% compared with the control group (E1). Choline supplementations before Cd stress (E5) increased TPC by 33%, while the Cd group (E2) decreased it by 18%, moreover, when choline was applied after Cd stress (E3), no change was observed compared to the control group. These data suggest that choline prevents inhibition of plant growth due to Cd toxicity by reducing Cd uptake. The results provided in the present study are likely to enhance the quality and efficiency of crop production in heavy metal-polluted areas.

ZmLSD1 Enhances Salt Tolerance by Regulating the Expression of ZmWRKY29 in Maize.

Salt stress significantly impairs plant growth, presenting a challenge to agricultural productivity. Exploring the regulatory mechanisms underlying salt stress responses is critically important. Here, we identified a significant role for the maize LESION-SIMULATING DISEASE transcription factor, ZmLSD1, in enhancing salt stress response. Subcellular localization analysis indicated that ZmLSD1-GFP was localized in the nucleus in the maize protoplast. Overexpressing ZmLSD1 in maize obviously enhanced the tolerance of plants to salt stress. Physiological analysis indicated that overexpressed ZmLSD1 in maize could mitigate the accumulation of H2O2 and MDA content exposed to salt stress. RNA-seq and qPCR-PCR analyses showed that ZmLSD1 positively regulated ZmWRKY29 expression. ChIP-qPCR and EMSA experiments demonstrated that ZmLSD1 could directly bind to the promoter of ZmWRKY29 through the GTAC motif both in vitro and in vivo. Overall, our findings suggest that ZmLSD1 plays a positive role in enhancing the tolerance of maize to salt by affecting ZmWRKY29 expression.

Influence of Potentially Toxic Elements and Physio-Chemical Parameters of Industrially Contaminated Soil on Arbuscular Mycorrhizal Fungal Diversity in BBN Corridor, Himachal Pradesh, India

ABSTRACT Arbuscular mycorrhizal fungi (AMF) play an essential role in plant growth and have great potential to enhance plant tolerance under polluted and toxic conditions. This study deals with a survey of five contaminated sites of the Baddi Barotiwala Nalagarh (BBN) industrial corridor/hub to investigate the morpho-diversity of endotrophic AM fungi associated with native plants. The high contamination factor of Cd and Fe in different study sites revealed a high intensity of contamination, indicating that the sites were significantly polluted with Cd and Fe. Results showed that AM symbioses were successfully established in the roots of native plants, highlighting their role in mitigating the harmful effects of potentially toxic elements (PTEs) through bioremediation. A total of 50 AMF morphotypes across 9 genera (Acaulospora, Entrophospora, Ambispora, Diversispora, Gigaspora, Scutellospora, Glomus, Rhizophagus, and Sclerocystis) were identified, with Glomeraceae being the most abundant (46%), followed by Acaulosporaceae (39%) and others contributing less (15%). The study also indicated that the hyphal and vesicular infections were prominent than arbuscular infections in roots. This is the first report on the diversity of native and putative AMF species associated with plants in the BBN industrial corridor, suggesting that these fungi could be cultured for further use as a sustainable organic approach in agriculture and rehabilitation practices in polluted areas.

Foliar application of esculin and digitoxin improve the yield quality of salt-stressed flax by improving the antioxidant defense system

BackgroundSecondary metabolites of several plants, including esculin and digitoxin, which are cardiac glycosides, were previously employed for their therapeutic effects. The current study aims to investigate the functions of the main Na+ /K+ transport inhibitor digitoxin and the antioxidant esculin for enhancing flax plant growth and production under salinity.MethodologyFlax plants were irrigated with distilled water supplemented with 0.0 and 5000 mg/L salt solution starting from 15 DAS from sowing. Then exogenous treatment with digitoxin and esculin with 50 mg L− 1 and 100 mg L− 1 were used for this work.ResultsAccording to the results of this work, foliar spraying of esculin or digitoxin increased the salinity tolerance of flax plants.The foliar application of either esculin or digitoxin induced an elevation in the contents of photosynthetic pigments, osmolytes including soluble sugar and proline as well as the total phenols in salt-stressed flax plants. Moreover, esculin and digitoxin in particular counteract oxidative stress by increasing the activity of antioxidant enzymes including superoxide dismutase, catalase, peroxidase, phenylalanine ammonia-lyase, and tyrosine ammonia lyase, leading to a decrease in reactive oxygen species and lipid peroxidation levels and electrolyte leakage. The efficiency of esculin and digitoxin to sustain ion homeostasis by inhibiting Na+ absorption and increasing potassium, calcium, and phosphorus in flax plants may be the reason for their protective actions towards salinity.As a consequence, esculin and digitoxin increased yield quantity and quality as shown by increases in all investigated yield criteriaas shoot height, root length, their fresh and dry weights as well asseed yield/plant (g), and 1000 seeds weight, especially those that improved the desired oil properties.ConclusionIn conclusion, this study concluded that digitoxin was more effective in inhibiting Na+ build-up and increasing flax salinity tolerance, particularly at the high investigated dose as compared to esculin. In this study, we reported the recent findings of exogenousapplication of either digitoxin or esculin glycosides which are new investigated salt alleviators never used before for improving the salt tolerance in flax plants.

Evaluating Native Bacillus Strains as Potential Biocontrol Agents against Tea Anthracnose Caused by Colletotrichum fructicola

Anthracnose of the tea plant (Camellia sinensis), caused by Colletotrichum spp., poses a significant threat to both the yield and quality of tea production. To address this challenge, researchers have looked to the application of endophytic bacteria as a natural alternative to the use chemical pesticides, offering potential for enhancing disease resistance and abiotic stress tolerance in tea plants. This study focused on identifying effective microbial agents to combat tea anthracnose caused by Colletotrichum fructicola. A total of 38 Bacillus-like strains were isolated from the tea rhizosphere, with 8 isolates showing substantial inhibitory effects against the mycelial growth of C. fructicola, achieving an average inhibition rate of 60.68%. Among these, strain T3 was particularly effective, with a 69.86% inhibition rate. Through morphological, physiological, and biochemical characterization, along with 16S rRNA gene phylogenetics analysis, these strains were identified as B. inaquosorum (T1 and T2), B. tequilensis (T3, T5, T7, T8, and T19), and B. spizizenii (T6). Biological and molecular assays confirmed that these strains could induce the expression of genes associated with antimicrobial compounds like iturin, fengycin, subtilosin, and alkaline protease, which effectively reduced the disease index of tea anthracnose and enhanced tea plant growth. In conclusion, this study demonstrates that B. inaquosorum, B. tequilensis, and B. spizizenii strains are promising biocontrol agents for managing tea anthracnose.

Diversity and Functional Roles of Root-Associated Endophytic Fungi in Two Dominant Pioneer Trees Reclaimed from a Metal Mine Slag Heap in Southwest China

The utilization of fast-growing, economically valuable woody plants with strong stress resistance, such as poplar and willow, to revegetate severely metal-contaminated mine tailings not only offers a productive and profitable use of abandoned polluted soil resources but also facilitates the phytoremediation of these polluted soils. This study examines the diversity and functional roles of endophytic fungi naturally colonizing the roots of an artificially established Populus yunnanensis forest and the naturally reclaimed pioneer species Coriaria sinica on an abandoned tailing dam in southwest China. Culture-independent analyses revealed that the root systems of both plant species were abundantly colonized by arbuscular mycorrhizal fungi and endophytic fungi, forming rich and diverse endophytic fungal communities predominantly represented by the genera Ilyonectria, Tetracladium, Auricularia, and unclassified members of Helotiales. However, the composition of root endophytic fungal communities differed significantly between the two plant species. Using a culture-dependent approach, a total of 192 culturable endophytic fungal strains were isolated from the roots. The dominant genera included Cadophora, Cladosporium, Cyphellophora, and Paraphoma, most of which were previously identified as dark septate endophytes (DSE). Six representative DSE strains were selected for further study, and significant cadmium tolerance and various plant growth-promoting traits were observed, including the solubilization of insoluble inorganic and organic phosphorus, indole-3-acetic acid (IAA) production, and siderophore synthesis. In greenhouse experiments, inoculating two DSE strains mitigated the inhibitory effects of metal-polluted tailing soil on the growth of P. yunnanensis. This was achieved by reducing heavy metal uptake in roots and limiting metal translocation to the above-ground tissues, thereby promoting plant growth and adaptability. Our findings suggest that as plants reclaim metal-polluted tailings, root-associated endophytic fungal communities also undergo natural succession, playing a critical role in enhancing the host plant’s tolerance to stress. Therefore, these restored root-associated fungi, particularly DSE, are essential functional components of the root systems in plants used for tailing reclamation.

Exploring the synergistic benefits of biochar and gibberellic acid in alleviating cadmium toxicity

Cadmium (Cd) toxicity significantly threatens agricultural productivity and food safety. Developing effective strategies to enhance plant tolerance to Cd stress is essential. This study investigates the synergistic effects of biochar (BC) and gibberellic acid (GA3) on mitigating Cd toxicity in maize (Zea mays), focusing on their impact on oxidative stress markers and antioxidant enzyme activities. Soil samples were collected from the Cholistan Institute of Desert Studies (CIDS) and analyzed for trace metal ions and other properties. Biochar was produced from fruit and vegetable waste, washed, washed, deashed, and mixed with 10 ppm GA3. FH-1036 hybrid maize seeds were sterilized and planted in pots containing soil with varying Cd levels (0, 8, and 16 mg Cd/kg soil). Twelve treatments were established, including control, GA3, BC, and their combinations under different Cd stress levels. Plants were irrigated to maintain 60% field capacity and harvested at the V10 growth stage. Hydrogen peroxide (H2O2) contents and activities of superoxide dismutase (SOD), peroxidase (POD), catalase (CAT), and ascorbate peroxidase (APX) were measured in roots, stems, and leaves. Statistical analysis was performed using OriginPro 2021, with ANOVA and Fisher’s LSD test used to determine significant differences. GA3 and BC treatments significantly reduced H2O2 levels in maize roots, stems and leaves under Cd stress. The combined treatment of GA3 + BC showed the most significant reduction in H2O2 levels across all plant parts, reducing root H2O2 by 50%, stem H2O2 by 55%, and leaf H2O2 by 53% under severe Cd stress (16 mg Cd/kg). SOD activity increased under non-stress conditions but decreased under Cd stress, with the highest activity observed in the combined treatment. POD activity followed a similar pattern, with GA3 + BC treatment resulting in the most significant increases under non-stress conditions and the least reductions under Cd stress. CAT activity showed substantial increases with GA3 + BC treatment, particularly under severe Cd stress, with a notable rise over the control. APX activity also exhibited enhancements with GA3 and BC treatments, especially in the combined treatment under various Cd stress levels. This study highlights the potential of combined BC and GA3 treatments in improving Cd stress tolerance in maize. Future research should focus on field trials and the long-term impacts of these treatments on crop productivity and soil health.

Genome-Wide Analysis of the Phospholipase Ds in Perennial Ryegrass Highlights LpABFs-LpPLDδ3 Cascade Modulated Osmotic and Heat Stress Responses.

The phospholipase Ds (PLDs) are crucial for cellular signalling and play roles in plant abiotic stress response. In this study, we identified 12 PLD genes from the genome data of perennial ryegrass (Lolium perenne), which is widely used as forage and turfgrass. Among them, LpPLDδ3 was significantly repressed by ABA treatment, and induced by drought stress and heat stress treatments. The ectopic overexpression (OE) of LpPLDδ3 in Arabidopsis enhanced plant tolerance to osmotic and heat stress as demonstrated by an increased survival rate and reduced malondialdehyde (MDA) accumulation and electrolyte leakage (EL). Arabidopsis endogenous ABA RESPONSIVE ELEMENT BINDING FACTORs (ABFs) and heat stress responsive genes were elevated in LpPLDδ3 OE lines under osmotic and heat stress treatments. Additionally, overexpression of LpPLDδ3 in perennial ryegrass protoplasts could increase heat stress tolerance and elevate expression level of heat stress responsive genes. Moreover, LpABF2 and LpABF4 depressed the LpPLDδ3 expression by directly binding to its ABRE core-binding motif of promoter region. In summary, LpPLDδ3 was repressed by LpABF2 and LpABF4 and positively involved in perennial ryegrass osmotic and heat stress responses.

A high-throughput protocol for testing heat-stress tolerance in pollen

AbstractViable pollen is crucial for fertilization, but pollen is generally highly susceptible to heat stress. A quick, reliable method for testing the heat-stress tolerance of pollen is needed to improve the heat-stress tolerance in plants, but current methods require considerable space and labor. In addition, many such methods only test tolerance to a single constant temperature, making it time-consuming to screen heat tolerance over a wide temperature range and to examine the dynamics of pollen viability at different temperatures. To address this issue, we aimed to: (1) develop an easy, reliable method for measuring pollen viability at different temperatures; and (2) identify the best temperature range for screening pollen with high heat-stress tolerance. We harvested mature pollen from wheat (Triticum aestivum) plants and transferred it to a 96-well plate filled with liquid medium containing sucrose. We placed the plate in a PCR machine operating under a gradient PCR program to simultaneously test a range of temperatures. After incubating the pollen for 4 h, at temperatures ranging from 21.9 to 47 °C, we examined the pollen grains under a light microscope and employed a specific image analysis pipeline to assess the effects of temperature on pollen morphology, germination, and tube growth. This method facilitated the high-throughput screening of many pollen samples, enabling rapid, reliable, and precise analysis of pollen viability in response to temperature. Our approach should be applicable to other plant species and could be used to identify quantitative trait loci or genes influencing heat stress tolerance in pollen for breeding programs.

Transcriptomic dynamics of ABA response in Brassica napus guard cells

Drought has a significant, negative impact on crop production; and these effects are poised to increase with climate change. Plants acclimate to drought and water stress through diverse physiological responses, primarily mediated by the hormone abscisic acid (ABA). Because plants lose the majority of their water through stomatal pores on aerial surfaces of plants, stomatal closure is one of the rapid responses mediated by ABA to reduce transpirational water loss. The dynamic changes in the transcriptome of stomatal guard cells in response to ABA have been investigated in the model plant Arabidopsis thaliana. However, guard cell transcriptomes have not been analyzed in agronomically valuable crops such as a major oilseed crop, rapeseed. In this study, we investigated the dynamics of ABA-regulated transcriptomes in stomatal guard cells of Brassica napus and conducted comparison analysis with the transcriptomes of A. thaliana. We discovered changes in gene expression indicating alterations in a host of physiological processes, including stomatal movement, metabolic reprogramming, and light responses. Our results suggest the existence of both immediate and delayed responses to ABA in Brassica guard cells. Furthermore, the transcription factors and regulatory networks mediating these responses are compared to those identified in Arabidopsis. Our results imply the continuing evolution of ABA responses in Brassica since its divergence from a common ancestor, involving both protein-coding and non-coding nucleotide sequences. Together, our results will provide a basis for developing strategies for molecular manipulation of drought tolerance in crop plants.

Biochemical and Transcriptomic Analyses Reveal Key Salinity and Alkalinity Stress Response and Tolerance Pathways in Salix linearistipularis Inoculated with Trichoderma

Soil salinization and alkalinization are pervasive environmental issues that severely restrict plant growth and crop yield. Utilizing plant growth-promoting rhizobacteria (PGPR) is an effective strategy to enhance plant tolerance to saline–alkaline stress, though the regulatory mechanisms remain unclear. This study employed biochemical and RNA-Seq methods to uncover the critical growth-promoting effects of Trichoderma spp. on Salix linearistipularis under saline–alkaline stress. The results showed that, during saline–alkaline stress, inoculation with Trichoderma sp. M4 and M5 significantly increased the proline and soluble sugar contents in Salix linearistipularis, enhanced the activities of SOD, POD, CAT, and APX, and reduced lipid peroxidation levels, with M4 exhibiting more pronounced effects than M5. RNA-Seq analysis of revealed that 11,051 genes were upregulated after Trichoderma sp. M4 inoculation under stress conditions, with 3532 genes primarily involved in carbon metabolism, amino acid biosynthesis, and oxidative phosphorylation—processes that alleviate saline–alkaline stress. Additionally, 7519 genes were uniquely upregulated by M4 under stress, mainly enriched in secondary metabolite biosynthesis, amino acid metabolism, cyanamide metabolism, and phenylpropanoid biosynthesis. M4 mitigates saline–alkaline stress-induced damage in Salix linearistipularis seedlings by reducing oxidative damage, enhancing organic acid and amino acid metabolism, and activating phenylpropanoid biosynthesis pathways to eliminate harmful ROS. This enhances the seedlings’ tolerance to saline–alkaline stress, providing a basis for studying fungi–plant interactions under such conditions.

Diethyl aminoethyl hexanoate ameliorates salt tolerance associated with ion transport, osmotic adjustment, and metabolite reprograming in white clover

BackgroundSoil salinization is a serious environmental hazard, limiting plant growth and production in different agro-ecological zones worldwide. Diethyl aminoethyl hexanoate (DA-6) as an essential plant growth regulator (PGR) exhibits a beneficial role in improving crop growth and stress tolerance. However, the DA-6-regulated effect and mechanism of salt tolerance in plants are still not fully understood. The objective of current study was to disclose salt tolerance induced by DA-6 in relation to changes in water and redox balance, photosynthetic function, ionic homeostasis, and organic metabolites reprogramming in white clover (Trifolium repens).ResultsA prolonged duration of salt stress caused water loss, impaired photosynthetic function, and oxidative injury to plants. However, foliar application of DA-6 significantly improved osmotic adjustment (OA), photochemical efficiency, and cell membrane stability under salt stress. In addition, high salinity induced massive accumulation of sodium (Na), but decreased accumulation of potassium (K) in leaves and roots of all plants. DA-6-treated plants demonstrated significantly higher transcript levels of genes involved in uptake and transport of Na and K such as VP1, HKT8, SOS1, NHX2, NHX6, and SKOR in leaves as well as VP1, HKT1, HKT8, H+-ATPase, TPK5, SOS1, NHX2, and SKOR in roots. Metabolomics analysis further illustrated that DA-6 primarily induced the accumulation of glucuronic acid, hexanoic acid, linolenic acid, arachidonic acid, inosose, erythrulose, galactopyranose, talopyranose, urea, 1-monopalmitin, glycerol monostearate, campesterol, stigmasterol, and alanine.ConclusionsThe DA-6 significantly up-regulated transcript levels of multiple genes associated with increased Na+ compartmentalization in vacuoles and Na+ sequestration in roots to reduce Na+ transport to photosynthetic organs, thereby maintaining Na+ homeostasis under salt stress. The accumulation of many organic metabolites induced by the DA-6 could be attributed to enhanced cell wall and membrane structural stability and functionality, OA, antioxidant defense, and downstream signal transduction in leaves under salt stress. The present study provides a deep insight about the synergistic role of DA-6 in salt tolerance of white clover.

Single and combined applications of dopamine and 24-epibrassinolide in soybean seedlings under water deficiency: tolerance mechanisms essential to inhibit deleterious effects

Water limitations often cause plants’ physiological, biochemical and morphological disorders, restricting their growth and performance and negatively impacting agricultural yield and global food security. Dopamine (DOP) is an essential water-soluble antioxidant, representing an exciting alternative for use in agriculture, as it maximises plant tolerance under adverse stress conditions. The 24-epibrassionolide (EBR) has the most bioactive function on plant metabolomics, being biodegradable and environmentally friendly. EBR can promote plant tolerance under stress conditions, including water deficiency. Therefore, this study aimed to verify the possible contributions of pre-treatment with DOP and EBR in soybean seedlings subjected to water deficiency, evaluating the responses linked to root anatomy, germination, antioxidant system and biomass accumulation. The single and combined use of growth regulators (DOP and EBR) mitigated the harmful effects caused by water deficiency in seedlings. However, the single use of DOP under the conditions of this research had better results. DOP and EBR positively affected root anatomy, modulating plastic changes in the epidermis tissues, metaxylem and vascular cylinder tissues. Increments in biomass and growth of seedlings exposed to drought and treated with growth regulators can be explained by the intense activities of antioxidant enzymes, maximising redox metabolism and protecting root tissues from oxidative damage.

The Maize Gene ZmGLYI-8 Confers Salt and Drought Tolerance in Transgenic Arabidopsis Plants.

Methylglyoxal (MG), a highly reactive and cytotoxic α-oxoaldehyde compound, can over-accumulate under abiotic stress, consequently injuring plants or even causing death. Glyoxalase I (GLYI), the first enzyme of the glyoxalase pathway, plays multiple roles in the detoxification of MG and in abiotic stress responses. However, the GLY1 gene in maize has been little studied in response to abiotic stress. In this study, we screened a glyoxalase I gene (ZmGLYI-8) and overexpressed in Arabidopsis. This gene was localized in the cytoplasm and can be induced in maize seedlings under multiple stress treatments, including salt, drought, MG, ABA, H2O2 and high temperature stress. Phenotypic analysis revealed that after MG, salt and drought stress treatments, overexpression of ZmGLYI-8 increased the tolerance of transgenic Arabidopsis to MG, salt and drought stress. Furthermore, we demonstrated that the overexpression of ZmGLYI-8 scavenges accumulated reactive oxygen species, detoxifies MG and enhances the activity of antioxidant enzymes to improve the resistance of transgenic Arabidopsis plants to salt and drought stress. In summary, this study preliminarily elucidates the molecular mechanism of the maize ZmGLYI-8 gene in transgenic Arabidopsis and provides new insight into the breeding of salt- and drought-tolerant maize varieties.

Diethyl aminoethyl hexanoate reprogramed accumulations of organic metabolites associated with water balance and metabolic homeostasis in white clover under drought stress.

Diethyl aminoethyl hexanoate (DA-6) serving as a non-toxic and low-cost plant growth regulator is used for improving plant growth and stress tolerance, but the DA-6-mediated organic metabolites remodeling in relation to drought tolerance is not well documented in crops. The aims of the present study were to evaluate impacts of DA-6 on physiological functions including osmotic adjustment, photochemical efficiency, oxidative damage, and cell membrane stability as well as organic metabolites remodeling in white clover (Trifolium repens) leaves based on the analysis of metabolomics. Plants were foliarly treated with or without DA-6 and subsequently exposed to drought stress for 8 days. Results demonstrated that foliar application of DA-6 (1.5 mM) could significantly ameliorate drought tolerance, which was linked with better leaf water status, photosynthetic performance, and cell membrane stability as well as lower oxidative injury in leaves. Metabolic profiling of organic metabolites identified a total of 59 metabolites including 17 organic acids, 20 sugars, 12 alcohols, and 10 other metabolites. In response to drought stress, the DA-6 induced accumulations of many sugars and sugar alcohols (erythrulose, arabinose, xylose, inosose, galactose, talopyranose, fucose, erythritol, and ribitol), organic acids (propanoic acid, 2,3-dihydroxybutanoic acid, palmitic acid, linolenic acid, and galacturonic acid), and other metabolites (2-oxazoline, silane, and glycine) in white clover. These altered metabolites induced by the DA-6 could perform critical functions in maintenances of osmo-protection, osmotic adjustment, redox homeostasis, cell wall structure and membrane stability when white clover suffered from water deficit. In addition, the campesterol and stigmasterol significantly accumulated in all plants in spite of the DA-6 pretreatment under drought stress, which could be an important adaptive response to water deficit due to beneficial roles of those two metabolites in regulating cell membrane stability and antioxidant defense. Present findings provide new evidence of DA-6-regulated metabolic homeostasis contributing to drought tolerance in leguminous plants.

Exogenous Melatonin Reinforces Photosynthesis, Antioxidant Defense and Gene Expression to Ameliorate Na2CO3 Stress in Maize.

Salt stress can seriously affect the growth and development of maize (Zea mays L.), resulting in a great yield loss. Melatonin (MT), an indole hormone, is a potential enhancer of plant tolerance against salt stress. However, the complex mechanisms of MT application in enhancing maize salt tolerance are still unclear. Herein, three-leaf seedlings of salt-susceptible P138 and its salt-resistant ethyl methane sulfonate (EMS)-104 mutant were cultured with or without 150 μM MT application under 0 and 100 mM Na2CO3 treatments for seven days, to systematically explore the response mechanisms of exogenous MT in improving the salt tolerance of maize. The results showed that salt stress triggered an escalation in reactive oxygen species production, enhanced multiple antioxidant enzymes' activities, impaired cellular membrane permeability, inhibited photosynthetic pigment accumulation, and ultimately undermined the vigor and photosynthetic prowess of the seedlings. While suitable MT application counteracted the detrimental impacts of Na2CO3 on seedlings' growth and photosynthetic capacity, the seedling length and net photosynthetic rate of P138 and EMS-104 were increased by 5.5% and 18.7%, and 12.7% and 54.5%, respectively. Quantitative real-time PCR (qRT-PCR) analysis further showed that MT application activated the expression levels of antioxidant enzyme-related genes (Zm00001d025106, Zm00001d031908, Zm00001d027511, and Zm00001d040364) and pigment biosynthesis-related genes (Zm00001d011819 and Zm00001d017766) in both maize seedlings under Na2CO3 stress; they then formed a complex interaction network of gene expression, multiple physiological metabolisms, and phenotype changes to influence the salt tolerance of maize seedlings under MT or Na2CO3 stress. To sum up, these observations underscore that 150 μM MT can alleviate salt injury of maize seedlings, which may provide new insights for further investigating MT regulation mechanisms to enhance maize seedlings' salt resistance.

Understanding of Plant Salt Tolerance Mechanisms and Application to Molecular Breeding.

Soil salinization is a widespread hindrance that endangers agricultural production and ecological security. High salt concentrations in saline soils are primarily caused by osmotic stress, ionic toxicity and oxidative stress, which have a negative impact on plant growth and development. In order to withstand salt stress, plants have developed a series of complicated physiological and molecular mechanisms, encompassing adaptive changes in the structure and function of various plant organs, as well as the intricate signal transduction networks enabling plants to survive in high-salinity environments. This review summarizes the recent advances in salt perception under different tissues, physiological responses and signaling regulations of plant tolerance to salt stress. We also examine the current knowledge of strategies for breeding salt-tolerant plants, including the applications of omics technologies and transgenic approaches, aiming to provide the basis for the cultivation of salt-tolerant crops through molecular breeding. Finally, future research on the application of wild germplasm resources and muti-omics technologies to discover new tolerant genes as well as investigation of crosstalk among plant hormone signaling pathways to uncover plant salt tolerance mechanisms are also discussed in this review.

Response of Alternaria and Fusarium Species to Low Precipitation in a Drought-Tolerant Plant in Morocco

The plant mycobiome plays a crucial role in the host life cycle, influencing both healthy and diseased states, and is essential for plant tolerance to drought. In this study, we used ITS metabarcoding to investigate the fungal community of the drought-resistant plant Malva sylvestris L. in Morocco along a gradient of precipitation, encompassing subhumid and semi-arid environments. We sampled three biotopes: rhizosphere, bulk soil, and root endosphere. Our findings revealed an absence of beta-diversity differences between bulk soil and rhizosphere, indicating that the plant does not selectively influence its rhizosphere mycobiome. Additionally, ASVs belonging to the genus Alternaria represented up to 30% of reads in the plant’s roots and correlated with drought (p = 0.006), indicating a potential role for this fungal genus in mitigating drought, possibly as part of the dark septate endophyte group. Root staining and microscopic observation revealed extensive colonization by fungal hyphae and microsclerotia-like structures. Furthermore, ASVs identified as Fusarium equiseti were also correlated with low precipitation and recognized as a hub taxon in the roots. However, it remains uncertain whether this species is pathogenic or beneficial to the plant. These insights contribute to our understanding of the plant mycobiome’s role in drought tolerance and highlight the importance of specific fungal taxa in supporting plant health under varying environmental conditions. Future research should focus on characterizing these taxa’s functional roles and their interactions with the host plant to further elucidate their contributions to drought resistance.