BACKGROUND: Damage-associated molecular patterns (DAMPs), which are recognised by specific plant receptors and trigger downstream signaling cascades that control various functions within plants, have recently emerged as key regulators of plant physiology. Over the years, researchers have identified novel peptides like systemin and HypSys to play crucial roles in defense, and their thorough characterisation has highlighted their biotechnological potential. Plants, being repositories of such compounds, encourage researchers to explore this seemingly limitless potential. Thus, in this study, we investigated IbPep1, an elicitor peptide identified in sweet potato (Ipomoea batatas), to assess its effects on plant metabolism and its potential role in defence responses. RESULTS: We generated a sweet potato cell suspension culture and analysed its response to the recently discovered plant elicitor peptide, IbPep1 in comparison with other known elicitors, including flg22. In contrast to the latter, IbPep1 did not elicit a significant ROS burst but at higher concentration peptide treatment significantly increased JA-Ile concentration. The levels of free amino acids remained unaffected. Strikingly, untargeted metabolomics revealed that IbPep1 mostly affected the shikimate and phenylpropanoid pathways and volatiles’ analysis showed a stimulated emission of sesquiterpenes by IbPep. CONCLUSIONS: The structural diversity and incompatibility between families make the study of Peps challenging. However, due to their widespread presence in angiosperms, they are attractive targets for biotechnological applications. In our study, we compared the effects of IbPep1 with those of known elicitors and discovered that its regulatory functions share some similarities with signaling peptides from other plant families, while also revealing novel effects such as the regulation of volatile compounds. These results shed light on the signaling activity of IbPep1 and its impact on specialised metabolic pathways, emphasising its potential role in plant defence and metabolic regulation.

Small RNAs (sRNAs) have emerged as central regulators of gene expression, coordinating development, stress responses, and immunity across plant tissues. Far from acting solely within individual cells, sRNAs move through plasmodesmata and the phloem to mediate systemic silencing, forming a long-distance communication network that parallels classical hormonal signaling. This review synthesizes current evidence for sRNA mobility in plants and its extension across species boundaries during host-pathogen interactions. We describe how sRNAs are stabilized by RNA-binding proteins, Argonaute complexes, and extracellular vesicles (EVs), and how these carriers enable selective trafficking within the plant and into fungal or oomycete pathogens. Cross-kingdom RNA interference (ckRNAi) forms the mechanistic basis of Host-Induced Gene Silencing (HIGS) and Spray-Induced Gene Silencing (SIGS), two emerging RNA-based strategies for crop protection. We also addressed the variability of RNA uptake among pathogens, environmental instability of naked RNAs, and the promise of nanocarriers, synthetic biology, and machine-learning design tools to overcome these barriers. Bioinformatic and regulatory challenges, ranging from the identification of functional mobile RNAs to risk assessment and field validation remain key frontiers. Collectively, these advances position mobile RNAs as both mechanistic signals and deployable tools, redefining plant-microbe communication and opening new paths toward predictive, sustainable RNA-driven agriculture.

Crop plants are attacked by multiple pests, inducing metabolic changes that shape interactions across trophic levels and influence the effectiveness of biological control. We examined how infestation by the coccoids Coccus viridis (scales) and Planococcus citri (mealybugs) modulates phytohormones, secondary metabolites, herbivore infestation, and behavior of the predator Cryptolaemus montrouzieri in Coffea arabica plants. Infestation by either scales or mealybugs activated the salicylate pathway but differentially regulated jasmonates and selected secondary metabolites. Scale infestation reduced mealybug performance, coinciding with elevated theophylline levels, whereas mealybugs activated jasmonates and upregulated several metabolites, including caffeine and catechin. The ladybug consumed coccoid pests and preferred mealybugs, but did not discriminate between scale- or mealybug-infested plant volatiles, suggesting limited specificity of herbivore-induced volatile blends in guiding predator foraging. Multiple infestation disrupted volatile-mediated attraction of the female ladybug. Our findings reveal the complexity of plant responses under multiple infestation and highlight species-specific interactions shaping tritrophic dynamics.

Jasmonates (JAs)-mediated pathways are central signaling hubs in plant defense responses. However, the identification of mobile and nonmobile signals involved in downstream systemic signaling is still less studied. Here, we investigate the role of the jasmonic acid-isoleucine (JA-Ile) conjugating enzyme, JAR1, in shifting wound-induced local and systemic metabolic profiles using liquid chromatography mass spectrometry (LC-MS/MS) for untargeted metabolomics, and the mobility of JA-Ile in wound-induced local and systemic defense using LC-MS/MS for targeted JAs analysis in Arabidopsis thaliana leaves. The use of jarin-1, a specific inhibitor of JA-Ile biosynthesis, suggested that JA-Ile was synthesized de novo in the particular tissues, rather than being a mobile signal. In addition, inhibition of JAR1 enzyme activity affected an array of downstream metabolic pathways, locally and systemically, such as amino acids and carbohydrate metabolism. This study suggests that the occurrence and spread of local and systemic downstream signals very likely depend on JAR1 activity, and this enzyme exclusively regulates a series of metabolic pathways under both wounding and nonwounding conditions.

Powdery mildew, caused by the obligate biotroph Erysiphe necator, represents a major threat to grapevine production worldwide. Host-mediated resistance offers a sustainable alternative to chemical fungicides. To elucidate the role of plant membrane lipid modifications and oxylipin accumulation in pathogen perception and response, a controlled infection experiment was conducted comparing a resistant hybrid (NY_39) from the Edmund Mach Foundation germplasm collection with a susceptible variety (cv. ‘Teroldego’). A lipidomic approach was integrated with hormone profiling and lipoxygenase (LOX) gene expression analysis. Significant lipid modulation was observed following E. necator inoculation, highlighting the plasticity of membrane and storage lipids metabolism. A rapid decrease in triacylglycerol content was measured in NY_39 at 12 h post-inoculation (hpi), whereas the opposite trend occurred in ‘Teroldego’, suggesting divergent metabolic rearrangements. A fast galactolipids peroxidation occurred in NY_39, while a delayed accumulation of phosphatidic acid was observed in ‘Teroldego’ at 48 hpi. The resistant genotype exhibited higher constitutive levels of salicylic acid as well as the expression of the VviAMP1 defensin, a small cysteine-rich protein with broad-spectrum antifungal activity. VviPR10-s11 and VviWRKY51, related to the synthesis of lignin and stilbenoid phytoalexins, were induced at 12 hpi in both genotypes. Within the LOX family, significant up-regulation of the 9-LOX VviLOX1a and the 13-LOXs VviLOX9 and VviLOXO was specific to ‘Teroldego’ at 12 hpi, despite a higher constitutive level of VviLOX9 in NY_39. This work identifies key metabolic, signalling and gene expression features in the selected hybrid that may be relevant for resistance. These include rapid triacylglycerols degradation, galactolipid peroxidation, constitutive higher SA level and expression of the defensin VviAMP1.

Although the regulatory role of changes in apoplastic pH (pHapo) in response to environmental conditions is well documented in root signalling, its contribution to guard cell (GC) regulation and the stress response to NaCl remains poorly understood. To determine whether alterations in leaf pHapo modulate physiological responses in GCs under NaCl stress, hydroponically grown Vicia faba plants were subjected to root-applied NaCl stress or alkaline-buffered infiltration of the leaf apoplast. In vivo monitoring of pHapo was coupled with transcriptomic, proteomic, and phytohormone profiling of samples enriched for GCs. Leaf apoplastic alkalinisation triggered distinct transcriptomic and proteomic responses in GCs. Among over 57 000 transcripts, 1562 were associated with pHapo, including 577 previously uncharacterised reading frames. Eighteen genes and two proteins responded consistently in both treatments, highlighting their responsiveness to shifts in leaf pHapo. These molecular changes accompanied NaCl-induced stomatal closure and rising GC-intrinsic ABA. Apoplastic alkalinisation in response to NaCl was closely linked to increased ABA levels, along with transcriptomic and proteomic shifts in the GCs. The temporal pattern suggests that the rise in pHapo functions as an initiating signal that triggers downstream molecular changes that occur before the stress becomes physiologically visible as stomatal closure.

Fusarium verticillioides is a widespread pathogen in cereals that reduces crop yields and poses a threat to food safety by producing the secondary metabolites fumonisins. Maize lipoxygenase genes (LOXs) are involved in the biosynthesis of oxylipins that function as signals in regulating defense. Previously, we showed that mutation of LOX4 is associated with susceptibility to Fusarium verticillioides in kernels, seedlings, and ears via alterations in both transcript profiles and LOX enzymatic activity. In this current study, we show that LOX4 overexpression results in enhanced resistance to pathogen infection and fumonisin contamination, substantiating its role in defense. Transcriptomic and lipidomic analyses revealed that LOX4 overexpression up-regulated expression of 9-LOX genes, thereby increasing the production of 9-oxylipin under fungal infection. The increased expression of jasmonic acid-related genes observed in infected plants was enhanced when LOX4 was overexpressed, correlating with wider accumulation of jasmonic acid-related metabolites. Our results indicate that LOX4 is a good target gene for future engineering of cultivars with increased resistance to F. verticillioides.

In modern agriculture, microbial inoculants isolated and collected from all over the world have gained popularity as a means of reducing the amount of fertilizer by increasing the availability of nutrients and mitigating environmental stress that is often connected with climate change. Concerning biocontrol, microbial inoculants are known to be effective in integrated pest management. However, the introduction of alien microbes can lead to the emergence of antagonists of the natural soil microbiota, which might drastically change the latter and ultimately have a negative impact on the whole natural soil ecosystem, causing unforeseeable consequences. We will discuss various aspects of the employment of microbial inoculants in agriculture, with a focus on the largely neglected threat posed by potentially invasive microbes.

Thyme species are important medicinal herbs predominantly cultivated in arid regions. They increasingly experience the adverse effects of climate change, particularly drought. Although abiotic stress effects on thyme have been examined, limited information exists on insect herbivory or combined stress response. This study investigated the effects of drought stress, herbivory and their combination on secondary metabolism, phytohormone regulation and insect performance in three thyme species: Thymus serpyllum (drought-sensitive), T. kotschyanus (drought-tolerant), and T. vulgaris. Plants were exposed for three weeks to four treatments: control, drought (40% field capacity), Spodoptera littoralis larvae herbivory, and combined drought × herbivory. Herbivore performance was documented. Levels of volatile terpenes, phenolic compounds, and phytohormones were analyzed using GC-MS and LC-MS/MS. Gene expression of terpenoid biosynthesis enzymes (TPS2, CYP71D178, CYP71D181) was quantified via RT-qPCR. Results revealed species-specific responses in secondary metabolism and measured gene expression, with herbivory exerting stronger effects than drought. Combined stress triggered the strongest responses in T. vulgaris and T. serpyllum, whereas T. kotschyanus tended to respond more to individual stressors. In contrast to species-specific metabolic responses, phytohormones exhibited treatment-specific patterns, with herbivory inducing the most pronounced changes across all measured phytohormones. Hormonal and metabolic adaptations were associated with reduced larval performance on stressed plants. Overall, the results show that the thyme species studied here respond to drought and herbivory through species-specific modulations of secondary metabolism. The integration of transcriptome, metabolome and phytohormone data provides new insights into the dynamic responses of Mediterranean aromatic plants to abiotic, biotic and combined stress factors, with implications for plant protection and resilience under climate change scenarios.

ZmWRKY125 negatively regulates maize resistance to Fusarium verticillioides infection through modulating phytohormone, ROS scavenging and secondary metabolite gene expression as well as jasmonic and abscisic acid biosynthetic pathway activity. Fusarium verticillioides causes heavy damage to maize growth and yield and is responsible for mycotoxin contamination. Despite its widespread occurrence, few resistant genes have been identified and functionally validated for their role in the defense mechanisms against this fungus in maize. WRKY transcription factors are known to be crucial in regulating the expression of defense-responsive genes towards pathogen attack. In this context, in our previous genome-wide association study one SNP in the gene ZmWRKY125 was found significantly associated with the responses to F. verticillioides infection in maize seedlings. Here, loss-of-function mutant lines of ZmWRKY125 were obtained by the clustered regularly interspaced short palindromic repeats (CRISPR)-associated protein 9 (Cas9) system. The zmwrky125 edited lines were phenotypically evaluated showing a decrease by about 5 and 4 times of Fusarium ear rot (FER) severity and fumonisin contamination, respectively, compared to the wild-type genotype. The transient expression of ZmWRKY125 in maize protoplasts confirmed a nuclear localization as expected for a transcription factor. RNA-seq analysis comparison using two zmwrky125 edited lines and the wild-type genotype highlighted an enhanced modulation of the jasmonic acid (JA) and abscisic acid (ABA) hormones, redox state, cell wall modification, and secondary metabolism-associated genes after fungal infection. Moreover, the increased expression of JA- and ABA-related genes correlated with a wider accumulation of these two phytohormones in the mutant background in contrast to wild-type. This data provided new information for understanding the function of ZmWRKY125, despite further field evaluations will be required for validation of the resistance against FER.

Plants are challenged regularly with multiple types of biotic stress factors, such as pathogens or insect herbivores, in their environment. To detect and defend against pathogens, plants have evolved an innate immune system in which intracellular receptors in the so-called effector-triggered immunity play a vital role. In Arabidopsis thaliana the Toll/interleukin-1 receptors (TIRs) domain is related to intracellular immunity receptors, for example in TIR-NBS-LRR (TNL) proteins. Among the TIR domain carrying proteins, very little is known about the function of the TIR-X proteins. Here, we focus on the recently described TIR-X (TIRP; At5g44900) to analyze its role in phytohormone-mediated plant defense through gene expression and phytohormone quantification. Therefore, we employed two fungal pathogens, the necrotrophic Alternaria brassicicola and the hemibiotrophic Verticillium dahliae, to infect A. thaliana WT (Col-0), TIRP knock-out, and TIRP overexpressing lines for comparative analyses. Furthermore, we included the insect herbivore Spodoptera littoralis and a treatment with S. littoralis egg extract on the plants to analyze any role of TIRP during these attacks. We found that both A. brassicicola and V. dahliae infections increased TIRP gene expression systemically. The salicylic acid content was higher in the TIRP overexpressing line, corresponding to a better S. littoralis larval growth performance in feeding assays. However, since we never observed clear infection-related differences in jasmonate or salicylic acid levels between the wild type and the two transgenic Arabidopsis lines, our results rule out the possibility that TIRP acts via the regulation of phytohormone synthesis and accumulation.

Thyme species, including Thymus vulgaris, T. kotschyanus (drought-tolerant) and T. serpyllum (drought-sensitive), are valuable medicinal herbs. They are often grown in arid regions and are increasingly suffering from water stress due to climate change. Here, we analyzed the metabolome and expression of selected genes in leaves of these species under drought stress with and without treatment with the phytohormone abscisic acid (ABA). Among the terpenes, dominant metabolites in thyme, thymol was the most important terpenoid component, followed by thymoquinone, carvacrol and p-cymene in all three species. Drought stress reduced terpene concentrations, while moderate ABA levels increased them. T. kotschyanus showed the highest concentrations of thymol and carvacrol after combined treatment with drought and ABA. Metabolite accumulation was partially correlated with genes related to terpenoid biosynthesis. The combined treatment of drought stress and ABA resulted in a significant reduction of the stress hormone jasmonic acid and an increase of its biosynthetic precursor, OPDA (cis-12-oxophytodienoic acid), in all species. The present research results indicate that ABA treatment at moderate concentrations could be used as a measure to increase the production of some pharmaceutically active phenolic monoterpenes in T. vulgaris, T. serpyllum and T. kotschyanus and increase the stress resistance of the plants.

High soil salinity affects plant growth, yield, and water use efficiency, leading to drought and ion toxicity. Silicon (Si), a crucial element in soil, can mitigate such stress. Si neutralizes harmful impacts, reduces Na+ uptake, and promotes plant growth. It benefits higher plants like grasses and cultivated crops. However, its role in maize cultivars is rarely reported. The present study aimed to evaluate the impact of exogenous Si application on maize plant growth, physiology, gene activation, and phytohormonal regulation under salinity stress. Therefore, a hydroponic experiment was conducted to study the impact of salt (100 mM NaCl) on two different maize varieties, the salt-sensitive Jalal and the salt-tolerant Iqbal, along with and without Si enrichment in pots or Si foliar spray. Our findings revealed that various phenotypical growth parameters as well as physiological parameters were significantly affected due to salt stress. However, the presence of Si mitigated the stress responses in both varieties. Moreover, we found that Si application reduced the NaCl-induced effects on abscisic acid and jasmonates in both varieties. Based on our findings, we concluded that Si application may lead to a reduction of NaCl-mediated salt stress on maize plants and help the plant to grow better.

Assembling and remodelling the cell wall is essential for plant development. Cell wall dynamics are controlled by cell wall proteins, polysaccharide biosynthesis, and a variety of sensor and receptor systems. LecRK-I.9, an Arabidopsis thaliana plasma membrane-localized lectin receptor kinase, was previously shown to be involved in cell wall-plasma membrane contacts and to play roles in plant-pathogen interactions, but until now its role in development was not known. LecRK-I.9 is transcribed at a high level in root tissues including the pericycle. Comparative transcript profiling of a loss-of-function mutant versus the wild type identified LecRK-I.9 as a regulator of cell wall metabolism. Consistently, lecrk-I.9 mutants displayed an increased pectin methylesterification level correlated with decreased pectin methylesterase and increased polygalacturonase activities. Also, LecRK-I.9 negatively impacted lateral root development through the direct or indirect regulation of genes encoding (i) cell wall remodelling proteins during early events of lateral root initiation, and (ii) cell wall signalling peptides (CLE2 and CLE4) repressing lateral root emergence and growth. Furthermore, low nitrate reduced LecRK-I.9 expression in roots, particularly in the lateral root emergence zone: even in these conditions, the control of CLE2 and CLE4 expression is maintained. Altogether, the results show that LecRK-I.9 is a key player in negatively regulating both pre-branch site formation and lateral root emergence.

The phyllosphere microbiome plays a crucial role in plant adaptation to environmental conditions, yet little is known about its variation across climate extremes. We profiled leaf-associated (epiphytic + endophytic) microbial communities of bilberry (Vaccinium myrtillus) from temperate (Jena, Germany) and Arctic (Tromsø, Norway) sites using shotgun metagenomics. Taxonomic and functional profiles revealed region-associated differences alongside a shared core microbiome. While alpha diversity did not differ significantly, ordination suggested a trend toward trend-associated compositional differences. Trait summaries indicated that taxa enriched in Tromsø commonly carried features linked to cold and oxidative-stress resilience, whereas Jena-enriched taxa tended toward faster growth and facultative metabolism. Despite the limited sample size and one site per region, these patterns are consistent with environment-associated filtering of phyllosphere communities. Our findings provide a descriptive baseline for targeted, hypothesis-driven tests of microbial functions relevant to plant resilience under shifting climates and suggest that V. myrtillus has potential as a model for studying climate-microbiome interactions in perennial plants.

Date palm (Phoenix dactylifera L.) is an important crop in arid regions and it is well adapted to desert ecosystems. To understand its remarkable ability to grow and yield in water-limited environments, we conducted experiments in which water was withheld for up to 4 weeks. In response to drought, root, rather than leaf, osmotic strength increased, with organic solutes such as sugars and amino acids contributing more to the osmolyte increase than minerals. Consistently, carbon and amino acid metabolism was acclimated toward biosynthesis at both the transcriptional and translational levels. In leaves, a remodeling of membrane systems was observed, suggesting changes in thylakoid lipid composition which, together with the restructuring of the photosynthetic apparatus, indicated an acclimation preventing oxidative damage. Thus, xerophilic date palm avoids oxidative damage under drought by combined prevention and rapid detoxification of oxygen radicals. Although minerals were expected to serve as cheap key osmotics, date palm also relies on organic osmolytes for osmotic adjustment in the roots during early drought acclimation. The diversion of these resources away from growth is consistent with the date palm strategy of generally slow growth in harsh environments and clearly indicates a trade-off between growth and stress-related physiological responses.

Leaf-cutting ants (Formicidae; Atta spp., Acromyrmex spp.) cut off pieces of leaves and other plant tissue and feed it to their symbiotic fungi. As this foraging behavior poses an imminent threat to agriculture, leaf-cutting ants are considered as pests of huge ecologically and economically importance. Consequently, research on leaf-cutting ants focused on their foraging decisions and interactions with their cultivated symbiotic fungi, whereas their effect on the attacked plants, apart from the loss of plant tissue, remains largely unknown. In this study, we investigated the consequences of an attack by leaf-cutting ants and analyzed the plants' defense responses in comparison to chewing caterpillars and mechanical damage. We found that an attack by leaf-cutting ants induces the production of jasmonates in several host and non-host plant species (Arabidopsis thaliana, Vicia faba, Phaseolus lunatus, Tococa quadrialata). Additionally, we showed in the natural host plant lima bean (P. lunatus) that leaf-cutting ant damage immediately leads to the emission of typical herbivory-induced plant volatiles, including green leaf volatiles and terpenoids. Further data exploration revealed clear differences in the defense-related phytohormone profile in plant species of Neotropical and Eurasian origin. Taken together, we show that leaf-cutting ant infestation and their way of clipping the plants' tissues induce jasmonate and jasmonates-mediated responses and do not differ from those to mechanical injury or larval feeding.

While ABA is often assumed to mediate partial stomatal closure as the soil dries, other plant hormones and hydraulic signals may also be involved. We tested whether irrigation volume (% of crop evapotranspiration, ET) and placement (partial rootzone drying [PRD] or deficit irrigation [DI], which irrigate part or all of the rootzone respectively) affect this signalling by measuring stomatal conductance (gs), leaf and shoot water potential (Ψleaf, Ψshoot), shoot xylem sap ABA concentration ([X-ABA]shoot) and various foliar hormones (ABA, IAA, SA, JA, JA-Ile and cis-OPDA) in cotton plants exposed to different irrigation volumes (100%ET or 50%ET) and placements (DI or PRD). Partial rootzone drying caused stomatal closure coincident with sustained foliar ABA accumulation and minimal changes in Ψshoot, but continued soil drying of the dry compartment reversed partial stomatal closure (with gs of 100%ET PRD plants sometimes greater than well-watered plants). With 100%ET PRD, partial stomatal closure correlated with decreased soil moisture of the dry compartment and increased [ABA]leaf, but neither Ψleaf nor [X-ABA]shoot. Irrespective of irrigation placement, 50%ET significantly decreased gs, Ψleaf and Ψshoot, but significantly increased [ABA]leaf, [X-ABA]shoot, [SA]leaf, [IAA]leaf and [cis-OPDA]leaf, with stomatal closure of 50%ET PRD plants occurring earlier than 50%ET DI plants. While stomatal closure at 50%ET correlated with foliar accumulation of multiple plant hormones, foliar ABA dynamics best explained transient stomatal closure at 100%ET PRD but not stomatal re-opening with prolonged soil drying. Thus, stomatal sensitivity to drying soil (and putative regulatory signals such as ABA) depended on irrigation volume and placement.