Prime Plant Research Articles

Climate change does not impact the water flow of barley at the vegetative stage, ameliorates at anthesis and worsens after subsequent drought episodes

Climate change will bring the interaction of stresses such as increased temperature and drought under high [CO2] conditions. This is likely to impact on crop growth and productivity. This study aimed to (i) determine the response of barley water relations to vegetative and anthesis drought periods under triple interaction conditions, (ii) test the possibility to prime barley plants for drought, and (iii) analyse the involvement of aquaporins in (i) and (ii). The water status of barley was not affected by drought at the vegetative stage, regardless of the environmental conditions. At the anthesis stage, when the water shortage period was more severe, barley plants growing under combined elevated CO2 and temperature conditions were able to maintain a better water status compared with plants grown under current conditions. Elevated CO2 and temperature conditions reduced the stomatal conductance and slowed down the plant water flow through a root-leaf hydraulic conductivity coordination. Leaf HvPIP2;1 and HvTIP1;1 aquaporins seemed to play a key role regulating barley's water flow, while leaf and root HvPIP2;5 provided basic level of water flow. At anthesis drought and under future combined conditions, plants showed a reduced cell dehydration and decrease in leaf relative water content compared with plants grown under current conditions. Exposure to a previous drought did not prime the water status of barley plants to a subsequent drought, but instead worsened the response under future conditions. This was due to an imbalance between the roots versus shoot development.

Overexpression of the transcription factor ANAC017 results in a genomes uncoupled phenotype under lincomycin.

Over-expression (OE) lines for the ER-tethered NAC transcription factor ANAC017 displayed de-repression of gun marker genes when grown on lincomycin (lin). RNA-seq revealed that ANAC017OE2 plants constitutively expressed greater than 40% of the genes induced in wild-type with lin treatment, including plastid encoded genes ycf1.2 and the gene cluster ndhH-ndhA-ndhI-ndhG-ndhE-psaC-ndhD, documented as direct RNA targets of GUN1. Genes encoding components involved in organelle translation were enriched in constitutively expressed genes in ANAC017OE2. ANAC017OE resulted in constitutive location in the nucleus and significant constitutive binding of ANAC017 was detected by ChIP-Seq to target genes. ANAC017OE2 lines maintained the ability to green on lin, were more ABA sensitive, did not show photo-oxidative damage after exposure of de-etiolated seedlings to continuous light and the transcriptome response to lin were as much as 80% unique compared to gun1-1. Both double mutants, gun1-1:ANAC017OE and bzip60:ANAC017OE (but not single bzip60), have a gun molecular gene expression pattern and result in variegated and green plants, suggesting that ANAC017OE may act through an independent pathway compared to gun1. Over-expression of ANAC013 or rcd1 did not produce a GUN phenotype or green plants on lin. Thus, constitutive ANAC017OE2 establishes an alternative transcriptional program that likely acts through a number of pathways, that is, maintains plastid gene expression, and induction of a variety of transcription factors involved in reactive oxygen species metabolism, priming plants for lin tolerance to give a gun phenotype.

Exogenous systemin peptide treatment in olive alters Bactrocera oleae oviposition preference

AbstractThe olive fruit fly, Bactrocera oleae (Rossi), is a key pest of the olive crop, whose control relies mostly on the use of insecticides. Plant peptides may represent a more environmentally-friendly tool to manage olive fly, due to their recognized role to activate and/or prime plant defence responses against pests. In this work, behavioural experiments (no-choice and two-choice) and analysis of volatile compounds were carried out to evaluate the impact of the exogenous application of the peptide systemin to olive tree on olive fly infestation, and to elucidate its mode of action to prime plant defence. The treatment of olive branches with 10 nM systemin showed to confer protection against olive fly, by reducing significantly the ovipositions (up to 3.0-fold) and the number of infested fruits (up to 2.9-fold) when compared to non-treated branches. This protective effect was even detected in neighbouring non-treated branches, suggesting the ability of systemin to trigger plant-to-plant communication. The deterrent activity of the primed olives was associated with the emission of the volatiles 2-ethyl-1-hexanol, 4-tert-butylcyclohexyl acetate and 1, 2, 3-trimethyl-benzene, which were negatively correlated with oviposition and fly infestation. Systemin has also showed to trigger the biosynthesis of specific volatiles (esters) in olives in response to fly attacks. Overall, the observed protection conferred by systemin against olive fly is likely due to the emission of specific volatiles that can act as a defence and/or as signalling molecules to upregulate the plant defence response. Thus, systemin represents a novel and useful tool to manage olive fruit fly.

Bio-Inspired Pressure-Dependent Programmable Mechanical Metamaterial with Self-Sealing Ability.

Self-sealing is one of the fascinating functions in nature that enables living material systems to respond immediately to damage. A prime plant model is Delosperma cooperi, which can rapidly self-seal damaged succulent leaves by systematically deforming until the wound closes. Inspired by this self-sealing principle, a novel programmable mechanical metamaterial has been developed to mimic the underlying damage management concept. This material is able to react autonomously to changes in its physical condition caused by an induced damage. To design this ability into the programmable metamaterial, a permeable unit cell design has been developed that can change size depending on the internal pressure. The parameter space and associated mechanical functionality of the unit cell design is simulated and analyzed under periodic boundary conditions and various pressures. The principles of self-sealing behavior in designed metamaterials are investigated, crack closure efficiency is identified for different crack lengths, the limitations of the proposed approach are discussed, and successful crack closure is experimentally demonstrated in the fabricated metamaterial. Although this study facilitates the first step on the way of integrating new bio-inspired principles in the metamaterials, the results show how programmable mechanical metamaterials might extend materials design space from pure properties to life-likeabilities.

Guardians of wheat: Unleashing transgenerational immune priming with Trichoderma against spot blotch

Plants encounter various biotic stresses in their natural habitat, prompting the exploration of innovative protective measures to bolster their immune defences against pathogens. An effective strategy involves priming plant immunity, conferring enduring and comprehensive protection. Defence priming, characterized by heightened responsiveness to attackers following prior stress exposure, intriguingly manifests transgenerationally, transmitting the memory of priming to subsequent plant generations. In our investigation, we delved into the phenomenon of transgenerational immune priming (TGIP) in wheat facilitated by Trichoderma, spanning from the parental generation (G0) to the grand progeny (G2) generation. Successful establishment of transgenerational priming in the G2 generation was achieved by initially priming the G0 generation of wheat with Trichoderma. To assess priming inheritance, seeds from the G1 generation were collected, and both primed and non-primed wheat plants' grand progeny (G2 generation) were cultivated in soil. Subsequent evaluation encompassed the disease phenotype, biochemical parameters, and yield-related traits of the G2 generation wheat when confronted with Bipolaris sorokiniana, the causal agent of spot blotch disease. Our analysis revealed that the G2 generation of primed wheat displayed superior protection against spot blotch compared to non-primed wheat. Biochemical studies indicated no activation of defensive responses in the absence of disease pressure in G2 wheat plants. However, upon pathogen challenge, the grand progeny of primed wheat exhibited a robust defence response, surpassing that of non-primed wheat. This targeted defence response enabled efficient resource utilization and mitigated yield penalties. Furthermore, under biotic stress conditions, the grand progeny of primed wheat exhibited enhanced yield parameters compared to non-primed wheat. Our findings provide conclusive evidence that Trichoderma-mediated priming against B. sorokiniana can be inherited successfully from the parental (G0) generation to the grand progeny (G2) generation of wheat. This study represents the initial documentation of Trichoderma-mediated TGIP in wheat against B. sorokiniana, holding significant promise for sustainable agriculture by offering an environmentally friendly alternative to chemical pesticides.

Priming avocado with sodium hydrosulfide prior to frost conditions induces the expression of genes involved in protection and stress responses.

Priming plants with chemical agents has been extensively investigated as a means for improving their tolerance to many biotic and abiotic stresses. Earlier, we showed that priming young avocado (Persea americana Mill cv. 'Hass') trees with sodium hydrosulfide (NaHS), a donor of hydrogen sulfide, improves the response of photosynthesis to simulated frost (cold followed by high light) conditions. In the current study, we performed a transcriptome analysis to gain insight into the molecular response of avocado 'Hass' leaves to frost, with or without NaHS priming. The analysis revealed 2144 (down-regulated) and 2064 (up-regulated) differentially expressed genes (DEGs) common to both non-primed and primed trees. Non-primed trees had 697 (down) and 559 (up) unique DEGs, while primed trees exhibited 1395 (down) and 1385 (up) unique DEGs. We focus on changes in the expression patterns of genes encoding proteins involved in photosynthesis, carbon cycle, protective functions, biosynthesis of isoprenoids and abscisic acid (ABA), as well as ABA-regulated genes. Notably, the differential expression results depict the enhanced response of primed trees to the frost and highlight gene expression changes unique to primed trees. Amongst these are up-regulated genes encoding pathogenesis-related proteins, heat shock proteins, enzymes for ABA metabolism, and ABA-induced transcription factors. Extending the priming experiments to field conditions, which showed a benefit to the physiology of trees following chilling, suggests that it can be a possible means to improve trees' response to cold stress under natural winter conditions.

Biochar: A Comprehensive Review on a Natural Approach to Plant Disease Management

Since time immemorial organic amendments have been an important strategy for improving soil fertility and suppressing a wide range of soil-borne pathogens. Biochar, a charcoal-like amendment has true potential in managing phytopathogens with an eco-friendly approach. It is produced by subjecting plant materials and agricultural waste to high temperatures of around 900°C in limited oxygen conditions. Biochar is considered to be an excellent carbon sequester and has an undeniably imperative role in improving soil properties. Biochar has innumerable applications in the remediation of environmental pollutants by immobilizing heavy metals such as Cadmium and Arsenic and degradation of dyes and pesticides. One of the most significant advantages of biochar in addition to mitigating environmental pollution is effectively managing plant pathogens by altering soil physical and chemical properties and promoting antagonistic microorganisms. Biochar directly suppresses plant pathogens by priming plant defense mechanisms. For instance, sugarcane bagasse biochar remediates Cd from contaminated soil, and citrus wood biochar induces systemic resistance against Botrytis cinerea in host-Lycopersicon esculentum, Capsicum annuum L. cv. Maccabi and Fragaria ananassa. Nevertheless, it is essential to acknowledge its limitations, such as the potential to absorb and enhance the residual activity of harmful chemicals. Further research is needed to develop a deeper understanding of biochar’s properties and mechanisms for more effective results. Advanced techniques like meta-transcriptomics and metaproteomics hold the potential to provide invaluable insights into this field. The review provides a comprehensive overview of current information regarding biochar, covering its production techniques and highlighting its agricultural benefits, with a particular focus on its role in plant disease management. Furthermore, the associated risks and concerns are also discussed.

High-resolution kinetics of herbivore-induced plant volatile transfer reveal clocked response patterns in neighboring plants.

Volatiles emitted by herbivore-attacked plants (senders) can enhance defenses in neighboring plants (receivers), however, the temporal dynamics of this phenomenon remain poorly studied. Using a custom-built, high-throughput proton transfer reaction time-of-flight mass spectrometry (PTR-ToF-MS) system, we explored temporal patterns of volatile transfer and responses between herbivore-attacked and undamaged maize plants. We found that continuous exposure to natural blends of herbivore-induced volatiles results in clocked temporal response patterns in neighboring plants, characterized by an induced terpene burst at the onset of the second day of exposure. This delayed burst is not explained by terpene accumulation during the night, but coincides with delayed jasmonate accumulation in receiver plants. The delayed burst occurs independent of day:night light transitions and cannot be fully explained by sender volatile dynamics. Instead, it is the result of a stress memory from volatile exposure during the first day and secondary exposure to bioactive volatiles on the second day. Our study reveals that prolonged exposure to natural blends of stress-induced volatiles results in a response that integrates priming and direct induction into a distinct and predictable temporal response pattern. This provides an answer to the long-standing question of whether stress volatiles predominantly induce or prime plant defenses in neighboring plants, by revealing that they can do both in sequence.

High-resolution kinetics of herbivore-induced plant volatile transfer reveal clocked response patterns in neighboring plants

Volatiles emitted by herbivore-attacked plants (senders) can enhance defenses in neighboring plants (receivers), however, the temporal dynamics of this phenomenon remain poorly studied. Using a custom-built, high-throughput proton transfer reaction time-of-flight mass spectrometry (PTR-ToF-MS) system, we explored temporal patterns of volatile transfer and responses between herbivore-attacked and undamaged maize plants. We found that continuous exposure to natural blends of herbivore-induced volatiles results in clocked temporal response patterns in neighboring plants, characterized by an induced terpene burst at the onset of the second day of exposure. This delayed burst is not explained by terpene accumulation during the night, but coincides with delayed jasmonate accumulation in receiver plants. The delayed burst occurs independent of day:night light transitions and cannot be fully explained by sender volatile dynamics. Instead, it is the result of a stress memory from volatile exposure during the first day and secondary exposure to bioactive volatiles on the second day. Our study reveals that prolonged exposure to natural blends of stress-induced volatiles results in a response that integrates priming and direct induction into a distinct and predictable temporal response pattern. This provides an answer to the long-standing question of whether stress volatiles predominantly induce or prime plant defenses in neighboring plants, by revealing that they can do both in sequence.

Copper and Silver Nanoparticle Seed Priming and Foliar Spray Modulate Plant Growth and Thrips Infestation in Capsicum spp.

Nanoparticles (NPs) have the potential to improve plant health and secondary metabolite production. In the present study, three different NPs, i.e., Ag, Cu, and Cu-Ag NPs were produced in the range from 25 to 86 nm, with zeta potentials ranging from -28.8 to -38.5 mV. The synthesized NPs were used for seed priming and foliar spray on three varieties of Capsicum annuum. L, i.e., Arka Sweta (AS), Arka Meghana (AM), and Arka Harita (AH) plants grown under greenhouse conditions. Seed priming at various concentrations of NPs (1, 10, 20 ppm) enhanced the seed germination (96%), seedling vigor index (2494-3112.66), seedling length (6-49%), and biomass (46%) of 45 days old Arka Meghana seedlings. Additionally, all plant tissues accumulated significantly higher amounts of chlorophyll (51-142%), carotenoids (23-94.2%), total phenolic content (73%), and total flavonoid content (57%), compared with the control (p ≤ 0.05). The foliar spray of NPs (20-100 ppm) has a protective effect on the chili plants against thrips infestation (30-76%). The foliar spray enhanced chlorophyll (15-62%), carotenoids (15-50%), total phenolic content (20-62%), total flavonoid content (64-99%), reducing sugars (15-97%), total antioxidant activity (15-142%), ferric reducing antioxidant power assay (15-109%), DPPH (129-54 mg mL-1), and capsaicinoids (capsaicin and dihydrocapsaicin) (82-128%). This study illustrates that Ag, Cu, and Cu-Ag NPs suppress thrips infestation and proliferation with enhanced plant growth and biochemical activity, which is inversely proportional to the NP size. Chemical NPs play a crucial role in the economic significance of chili plants, offering a promising avenue for developing pesticides to effectively combat thrips infestation. This advancement holds great potential in enhancing the overall agronomic productivity of the chili crops.

Cowpea volatiles induced by beet armyworm or fall armyworm differentially prime maize plants

Exposure to herbivore-induced plant volatiles (HIPVs) is known to enhance the defense responses in plants. This so-called priming effect has only been marginally studied in intercropping systems. We tested whether HIPVs from cowpea, which often serves as an intercrop alongside maize, can prime herbivore-induced volatile emissions in maize. Conventional volatile collection assays and real-time mass spectrometry revealed that maize plants that were exposed to HIPVs from cowpea infested with Spodoptera exigua caterpillars emitted more than control plants when they themselves were subsequently damaged by the same pest. The enhanced emission was only evident on the first day after infestation. Maize plants that were exposed to HIPVs from cowpea infested by S. frugiperda larvae showed no priming effect and released considerably less upon S. frugiperda infestation than upon S. exigua infestation. The latter may be explained by the fact that S. frugiperda is particularly well adapted to feed on maize and is known to suppress maize HIPV emissions. Our results imply that HIPVs from cowpea, depending on the inducing insect herbivore, may strongly prime maize plants. This deserves further investigation, also in other intercropping systems, as it can have important consequences for tritrophic interactions and crop protection.

Mechanisms of Primed Defense: Plant Immunity Induced by Endophytic Colonization of a Mycovirus-Induced Hypovirulent Fungal Pathogen.

How mycovirus-induced hypovirulence in fungi activates plant defense is still poorly understood. The changes in plant fitness and gene expression caused by the inoculation of the fungus Sclerotinia sclerotiorum harboring and made hypovirulent by the mycovirus soybean leaf-associated gemygorvirus-1 (SlaGemV-1) of the species Gemycircularvirus soybe1 were examined in this study. As the hypovirulent fungus (DK3V) colonized soybean Glycine max, plant transcriptomic analysis indicated changes in defense responses and photosynthetic activity, supported by an upregulation of individual genes and overrepresentation of photosystem gene ontology groups. The upregulated genes include genes relating to both pathogen-associated molecular pattern-triggered immunity and effector-triggered immunity as well as various genes relating to the induction of systemic acquired resistance and the biosynthesis of jasmonic acid. Plants colonized with DK3V showed a resistant phenotype to virulent S. sclerotiorum infection. Plant height and leaf area were also determined to be larger in plants grown with the virus-infected fungus. Here, we hypothesize that inoculation of soybean with DK3V can result in the triggering of a wide range of defense mechanisms to prime against later infection. The knowledge gained from this study about plant transcriptomics and phenotype will help prime plant immunity with mycovirus-infected hypovirulent fungal strains more effectively. [Formula: see text] Copyright © 2023 The Author(s). This is an open access article distributed under the CC BY-NC-ND 4.0 International license.

Drought Priming and Subsequent Irrigation Water Regimes Enhanced Grain Yield and Water Productivity of Wheat Crop

The most important factor impacting wheat production is water stress that occurs during the reproductive growth stage. Therefore, the plant responses and water productivity as affected by drought priming were investigated during Rabi seasons 2021 and 2022. The field trials were conducted in the research field of the Department of Irrigation and Drainage, Faculty of Agricultural Engineering, Sindh Agriculture University, Tandojam. The Hamal-BNS wheat variety was subjected to differing irrigation water regime levels (40%, 50% and 60% of soil water holding capacity, SWHC) after being subjected to drought priming, irrigation water recovery (water closure period) and drought priming. There were six treatments: (1) DPP-40 (drought priming plants at 40% of SWHC), (2) DPP-50, (3) DPP-60, (4) CTP-40 (controlled treated plants at 40% of SWHC), (5) CTP-50 and (6) CTP-60. During the experiment period, soil moisture content was significantly affected by the different treatments at various growth stages of wheat. The results indicated that winter wheat pre-exposed to drought priming attained a stress imprint that improved the subsequent deficit water levels which occurred during the later plant growth stage as demonstrated by the progress of test weight, grain yield, plant level water use efficiency and irrigation water use efficiency as well as relative yield compared to CTP-50 (control treatment). Under the irrigation water regime levels during the post-anthesis period, primed wheat plants sustained grain yield and higher relative yield than wheat plants without priming due to the better irrigation water regime for drought-primed wheat plants. Similarly, primed wheat plants consumed 18.3% less irrigation water as compared to non-primed plants, which significantly increased plant level WUE and irrigation WUE and decreased dry biomass and root development of drought-primed wheat plants. Therefore, to conserve fresh water for other field crops and increase water productivity in the Sindh province, it is recommended that drought priming is used during the early growth period of wheat plants as a successful irrigation method.

Root acclimations to soil flooding prime rice (Oryza sativa L.) for subsequent conditions of water deficit

Background and aimsThe root barrier to radial O2 loss is a trait induced during soil flooding restricting oxygen loss from the roots to the anoxic soil. It can also restrict radial water loss, potentially providing tolerance towards drought during conditions of water deficit. Several root traits (aerenchyma and xylem vessels area) respond in a similar way to soil flooding and low soil water potentials. Therefore, we hypothesised that root acclimations to soil flooding prime plants to withstand conditions of water deficit.MethodsWe raised plants in hydroponics mimicking contrasting soil water conditions (aerated controls for well-watered soils; stagnant, deoxygenated solutions for flooded soils, and aerated solutions with different PEG6000 concentrations to mimic conditions of water deficit). We used O2 microsensors and gravimetric measurements to characterize the formation of a barrier to radial O2 loss during conditions of water deficit, and measured key anatomical root traits using light microscopy.ResultsSeveral root traits were induced in stagnant conditions as well as in conditions of water deficit, including the barrier to radial O2 loss. The tightness of the barrier to water loss was similar in both stagnant and PEG6000 treatments. Moreover, plants growing in stagnant conditions tolerated a following severe condition of water deficit, whereas those growing in mimicked well-watered conditions did not.ConclusionsWe demonstrated that plants growing in stagnant conditions can withstand following severe conditions of water deficit. We propose that key root traits, such as the barrier to radial O2 loss, which are induced in stagnant conditions as well as mild conditions of water deficit, prime the plants for a following severe condition of water deficit.

Flagellin, a plant-defense-activating protein identified from Xanthomonas axonopodis pv. Dieffenbachiae invokes defense response in tobacco

BackgroundSecretome analysis is a valuable tool to study host-pathogen protein interactions and to identify new proteins that are important for plant health. Microbial signatures elicit defense responses in plants, and by that, the plant immune system gets triggered prior to pathogen infection. Functional properties of secretory proteins from Xanthomonas axonopodis pv. dieffenbachiae (Xad1) involved in priming plant immunity was evaluated.ResultsIn this study, the secretome of Xad1 was analyzed under host plant extract-induced conditions, and mass spectroscopic analysis of differentially expressed protein was identified as plant-defense-activating protein viz., flagellin C (FliC). The flagellin and Flg22 peptides both elicited hypersensitive reaction (HR) in non-host tobacco, activated reactive oxygen species (ROS) scavenging enzymes, and increased pathogenesis-related (PR) gene expression viz., NPR1, PR1, and down-regulation of PR2 (β-1,3-glucanase). Protein docking studies revealed the Flg22 epitope of Xad1, a 22 amino acid peptide region in FliC that recognizes plant receptor FLS2 to initiate downstream defense signaling.ConclusionThe flagellin or the Flg22 peptide from Xad1 was efficient in eliciting an HR in tobacco via salicylic acid (SA)-mediated defense signaling that subsequently triggers systemic immune response epigenetically. The insights from this study can be used for the development of bio-based products (small PAMPs) for plant immunity and health.

Floral biology insights into essential oil yield and chemical composition in davana (Artemisia pallens Bess), a high-value aromatic plant of India

Floral organs are identified as the major source of essential oil production in some prime aromatic plants. The quality and quantity of the essential oil are also influenced by the floral developmental stages. The present study was undertaken in A. pallens Bess (davana) with respect to its floral biology and floral sequence in relation to the essential oil yield and its chemical constituents for industrial extraction. The findings revealed that floral (inflorescence) biomass is the primary source of essential oil yield in davana, with the highest oil yield (0.90 ml/100 g) recovered during the blooming stage, followed by herbage (stems and leaves) biomass. Furthermore, cis-davanone, the major chemical constituent of davana essential oil, was recorded at a higher percentage in the bud stage (66.36±0.60%) followed by the blooming stage (60.56±0.20%) and the seed setting stage (40.54±0.80%). These findings can be used to optimize harvest timing in order to obtain higher quality and quantity of davana essential oil.

Jasmonate signaling drives defense responses against Alternaria alternata in chrysanthemum

BackgroundBlack spot disease caused by the necrotrophic fungus Alternaria spp. is one of the most devastating diseases affecting Chrysanthemum morifolium. There is currently no effective way to prevent chrysanthemum black spot.ResultsWe revealed that pre-treatment of chrysanthemum leaves with the methy jasmonate (MeJA) significantly reduces their susceptibility to Alternaria alternata. To understand how MeJA treatment induces resistance, we monitored the dynamics of metabolites and the transcriptome in leaves after MeJA treatment following A. alternata infection. JA signaling affected the resistance of plants to pathogens through cell wall modification, Ca2+ regulation, reactive oxygen species (ROS) regulation, mitogen‐activated protein kinase cascade and hormonal signaling processes, and the accumulation of anti-fungal and anti-oxidant metabolites. Furthermore, the expression of genes associated with these functions was verified by reverse transcription quantitative PCR and transgenic assays.ConclusionOur findings indicate that MeJA pre-treatment could be a potential orchestrator of a broad-spectrum defense response that may help establish an ecologically friendly pest control strategy and offer a promising way of priming plants to induce defense responses against A. alternata.

Hormonal involvement in boosting the vegetative vigour underlying caffeine-related improvements in lentil production

Previous studies have shown that caffeine (1,3,7-trimethylxanthine) has some potential for its use as a biostimulant ingredient for boosting lentil production at suboptimal temperatures. However, some limitations to its use include its potential side effects as an emerging contaminant and the current lack of knowledge of its mechanism of action. Here, we aimed to study the mechanisms underlying improved lentil production upon caffeine application. Greenhouse-grown plants treated with caffeine (at 10-5 M, 10-4 M, and 10-3 M) were compared to an untreated, control treatment, and both reproductive and vegetative vigour were evaluated in parallel with endogenous foliar concentrations of phytohormones, including both stress and growth-related hormones. Results showed an enhanced lentil production at the highest caffeine concentration (10-3 M) which might be attributed, at least in part, to a greater vegetative vigour. The hormonal profiling revealed a dual effect. Firstly, there was a specific increase in jasmonoyl-isoleucine (JA-Ile) in the short term, which may provide a priming effect. Secondly, abscisic acid (ABA) content kept at low levels and the active cytokinin (CK) isopentenyl adenine (2-iP) increased and persisted at high levels throughout the reproductive stage. Cytokinin-mediated effects on growth, and more specifically the high CK/ABA ratios in leaves, appeared to mediate caffeine-related effects in boosting vegetative vigour. In conclusion, caffeine emerges as a compelling alkaloid for integration into biostimulant formulations due to its favorable effect in boosting lentil production through an improvement of vegetative vigour. These outcomes appear to be modulated by phytohormones, most notably jasmonates, priming plants for improved performance under suboptimal temperatures, and cytokinins, alongside ABA and its associated ratios, collectively enhancing plant growth and reproductive vigour in challenging conditions.

Salt stress responses and alleviation strategies in legumes: a review of the current knowledge.

Salinity is one of the most significant environmental factors limiting legumes development and productivity. Salt stress disturbs all developmental stages of legumes and affects their hormonal regulation, photosynthesis and biological nitrogen fixation, causing nutritional imbalance, plant growth inhibition and yield losses. At the molecular level, salt stress exposure involves large number of factors that are implicated in stress perception, transduction, and regulation of salt responsive genes' expression through the intervention of transcription factors. Along with the complex gene network, epigenetic regulation mediated by non-coding RNAs, and DNA methylation events are also involved in legumes' response to salinity. Different alleviation strategies can increase salt tolerance in legume plants. The most promising ones are Plant Growth Promoting Rhizobia, Arbuscular Mycorrhizal Fungi, seed and plant's priming. Genetic manipulation offers an effective approach for improving salt tolerance. In this review, we present a detailed overview of the adverse effect of salt stress on legumes and their molecular responses. We also provide an overview of various ameliorative strategies that have been implemented to mitigate/overcome the harmful effects of salt stress on legumes.

Tissue-Specific Hormone Signalling and Defence Gene Induction in an In Vitro Assembly of the Rapeseed Verticillium Pathosystem.

Priming plants with beneficial microbes can establish rapid and robust resistance against numerous pathogens. Here, compelling evidence is provided that the treatment of rapeseed plants with Trichoderma harzianum OMG16 and Bacillus velezensis FZB42 induces defence activation against Verticillium longisporum infection. The relative expressions of the JA biosynthesis genes LOX2 and OPR3, the ET biosynthesis genes ACS2 and ACO4 and the SA biosynthesis and signalling genes ICS1 and PR1 were analysed separately in leaf, stem and root tissues using qRT-PCR. To successfully colonize rapeseed roots, the V. longisporum strain 43 pathogen suppressed the biosynthesis of JA, ET and SA hormones in non-primed plants. Priming led to fast and strong systemic responses of JA, ET and SA biosynthesis and signalling gene expression in each leaf, stem and root tissue. Moreover, the quantification of plant hormones via UHPLC-MS analysis revealed a 1.7- and 2.6-fold increase in endogenous JA and SA in shoots of primed plants, respectively. In roots, endogenous JA and SA levels increased up to 3.9- and 2.3-fold in Vl43-infected primed plants compared to non-primed plants, respectively. Taken together, these data indicate that microbial priming stimulates rapeseed defence responses against Verticillium infection and presumably transduces defence signals from the root to the upper parts of the plant via phytohormone signalling.