Activation Of Defense Mechanisms Research Articles

Medicago truncatula SOBIR1 controls pathogen immunity and specificity in the Rhizobium-legume symbiosis.

Medicago truncatula Nod Factor Perception (MtNFP)plays a role in both the Rhizobium-Legume (RL)symbiosis and plant immunity, and evidence suggests that the immune-related function of MtNFP is relevant for symbiosis. To better understand these roles of MtNFP, we sought to identify new interacting partners. We screened a yeast-2-hybrid cDNA library from Aphanomyces euteiches infected and noninfected M. truncatula roots. The M. truncatula leucine-rich repeat (LRR)receptor-like kinase SUPPRESSOR OF BIR1 (MtSOBIR1)was identified as an interactor of MtNFP and was characterised for kinase activity, and potential roles in symbiosis and plant immunity. We showed that the kinase domain of MtSOBIR1 is active and can transphosphorylate the pseudo-kinase domain of MtNFP. MtSOBIR1 could functionally complement Atsobir1 and Nbsobir1/sobir1-like mutants for defence activation, and Mtsobir1 mutants were defective in immune responses to A. euteiches. For symbiosis, we showed that Mtsobir1 mutant plants had both a strong, early infection defect and defects in the defence suppression in nodules, and both effects were plant genotype- and rhizobial strain-specific. This work highlights a conserved function for MtSOBIR1 in activating defence responses to pathogen attack, and potentially novel symbiotic functions of downregulating defence in association with the control of symbiotic specificity.

Phospholipid production and signaling by a plant defense inducer against Podosphaera xanthii is genotype-dependent.

Biotrophic phytopathogenic fungi such as Podosphaera xanthii have evolved sophisticated mechanisms to adapt to various environments causing powdery mildews leading to substantial yield losses. Today, due to known adverse effects of pesticides, development of alternative control means is crucial and can be achieved by combining plant protection products with resistant genotypes. Using plant defense inducers, natural molecules that stimulate plant immune system mimicking pathogen attack is sustainable, but information about their mode of action in different hosts or host genotypes is extremely limited. Reynoutria sachalinensis extract, a known plant defense inducer, especially through the Salicylic acid pathway in Cucurbitaceae crops against P. xanthii, was employed to analyze the signaling cascade of defense activation. Here, we demonstrate that R. sachalinensis extract enhances phospholipid production and signaling in a Susceptible to P. xanthii courgette genotype, while limited response is observed in an Intermediate Resistance genotype due to genetic resistance. Functional enrichment and cluster analysis of the upregulated expressed genes revealed that inducer application promoted mainly lipid- and membrane-related pathways in the Susceptible genotype. On the contrary, the Intermediate Resistance genotype exhibited elevated broad spectrum defense pathways at control conditions, while inducer application did not promote any significant changes. This outcome was obvious and at the metabolite level. Main factor distinguishing the Intermediate Resistance form the Susceptible genotype was the epigenetic regulated increased expression of a G3P acyltransferase catalyzing phospholipid production. Our study provides evidence on phospholipid-based signaling after plant defense inducer treatment, and the selective role of plant's genetic background.

Comparative analysis between a HLB tolerant bud sport obtained from the ‘Flame’ grapefruit with its parental genotype

Natural bud sports can lead to the development of plants with unique phenotypic traits such as changes in color, size, or disease resistance. In this report, biochemical, transcriptomic, and genomic analyses were conducted on a natural bud sport of the ‘Flame’ grapefruit compared to its wild-type genotype in response to Huanglongbing (HLB; Citrus greening) disease. The biochemical analysis of the bud sport genotype leaves revealed an increase in chlorophyll content and a decrease in starch accumulation compared to the wild-type genotype. Transcriptomic analysis identified significant differences between the bud sport and wild-type genotypes, with 738 genes being upregulated and 3899 genes downregulated. Differential expression of genes encoding for phloem proteins, phytohormones such as jasmonic acid and gibberellic acid, pathogenesis-related (PR) genes, and their negative regulators were observed in this study. Callose deposition-related genes were downregulated in the bud sport, suggesting that the bud sport ‘Flame’ grapefruit might modulate phloem genes in response to Candidatus Liberibacter asiaticus (CaLas) without excessive callose deposition. Overexpression of WRKY transcripts involved in pathogenesis-related (PR) gene expression, such as the NIM1 interacting 1 transcript, suggests activation of PR-mediated defense. Downregulation of carbohydrate metabolism and several major transporter transcripts may be responsible for resource allocation strategies to limit bacterial spread. Altered expression of some of the key genes and pathways in the bud sport produced a better response to CaLas than the wild-type following HLB infection, indicating that the bud sport may be modulating its defense strategies to cope against the pathogen. The SNP polymorphism identified through genotyping-by-sequencing determined meaningful genetic distinction between bud sport and wild-type genotypes derived from the same plant, facilitating precise genetic characterization and analysis.

UV-B Stress-Triggered Amino Acid Reprogramming and ABA-Mediated Hormonal Crosstalk in Rhododendron chrysanthum Pall.

Increased UV-B radiation due to ozone depletion adversely affects plants. This study focused on the metabolite dynamics of Rhododendron chrysanthum Pall. (R. chrysanthum) and the role of ABA in mitigating UV-B stress. Chlorophyll fluorescence metrics indicated that both JA and ABA increased UV-B resistance; however, the effect of JA was not as strong as that of ABA. Metabolomic analysis using UPLC-MS/MS (ultra-performance liquid chromatography and tandem mass spectrometry) revealed significant fluctuations in metabolites under UV-B and ABA application. UV-B decreased amino acids and increased phenolics, suggesting antioxidant defense activation. ABA treatment upregulated lipids and phenolic acids, highlighting its protective role. Multivariate analysis showed distinct metabolic clusters and pathways responding to UV-B and ABA, which impacted amino acid metabolism and hormone signal transduction. Exogenous ABA negatively regulated the JA signaling pathway in UV-B-exposed R. chrysanthum, as shown by KEGG enrichment. This study deepens understanding of plant stress-tolerance mechanisms and has implications for enhancing plant stress tolerance through metabolic and hormonal interventions.

Dual Transcriptomic and Metabolomic Analysis of Elicited Flax Sheds Light on the Kinetics of Immune Defense Activation Against the Biotrophic Pathogen Oidium lini.

Flax (Linum usitatissimum) grown under controlled conditions displayed genotype-dependent resistance to powdery mildew (Oidium lini) following COS-OGA (comprising chitosan- and pectin-derived oligomers) elicitor application. The present study reveals a two-step immune response in plants preventively challenged with the elicitor: an initial, rapid response characterized by the transcription of defense genes whose protein products act in contact with or within the cell wall, where biotrophic pathogens initially thrive, followed by a prolonged activation of cell wall peroxidases and accumulation of secondary metabolites. Thus, dozens of genes encoding membrane receptors, pathogenesis-related proteins, and wall peroxidases were initially overexpressed. Repeated COS-OGA treatments had a transient effect on the transcriptome response while cumulatively remodeling the metabolome over time, with a minimum of two applications required for maximal metabolomic shifts. Secondary metabolites, in particular terpenoids and phenylpropanoids, emerged as major components of this secondary defense response alongside pathogenesis-related proteins and wall peroxidases. The sustained accumulation of secondary metabolites, even after cessation of elicitation, contrasted with the short-lived transcriptomic response. Wall peroxidase enzyme activity also exhibited cumulative effects, increasing strongly for weeks after a third elicitor treatment. This underscores the plasticity of the plant immune response in the face of a potential infection, and the need for repeated preventive applications to achieve the full protective potential of the elicitor.

The bacterial defense system MADS interacts with CRISPR-Cas to limit phage infection and escape

The constant arms race between bacteria and their parasites has resulted in a large diversity of bacterial defenses, with many bacteria carrying multiple systems. Here, we report the discovery of a phylogenetically widespread defense system, coined methylation-associated defense system (MADS), which is distributed across gram-positive and gram-negative bacteria. MADS interacts with a CRISPR-Cas system in its native host to provide robust and durable resistance against phages. While phages can acquire epigenetic-mediated resistance against MADS, co-existence of MADS and a CRISPR-Cas system limits escape emergence. MADS comprises eight genes with predicted nuclease, ATPase, kinase, and methyltransferase domains, most of which are essential for either self/non-self discrimination, DNA restriction, or both. The complex genetic architecture of MADS and MADS-like systems, relative to other prokaryotic defenses, points toward highly elaborate mechanisms of sensing infections, defense activation, and/or interference.

The complex effects of modern oncogenic environments on the fitness, evolution and conservation of wildlife species.

Growing evidence indicates that human activities are causing cancer rates to rise in both human and wildlife populations. This is due to the inability of ancestral anti-cancer defences to cope with modern environmental risks. The evolutionary mismatch between modern oncogenic risks and evolved cancer defences has far-reaching effects on various biological aspects at different timeframes, demanding a comprehensive study of the biology and evolutionary ecology of the affected species. Firstly, the increased activation of anti-cancer defences leads to excessive energy expenditure, affecting other biological functions and potentially causing health issues like autoimmune diseases. Secondly, tumorigenesis itself can impact important fitness-related parameters such as competitiveness, predator evasion, resistance to parasites, and dispersal capacity. Thirdly, rising cancer risks can influence the species' life-history traits, often favoring early reproduction to offset fitness costs associated with cancer. However, this strategy has its limits, and it may not ensure the sustainability of the species if cancer risks continue to rise. Lastly, some species may evolve additional anti-cancer defences, with uncertain consequences for their biology and future evolutionary path. In summary, we argue that the effects of increased exposure to cancer-causing substances on wildlife are complex, ranging from immediate responses to long-term evolutionary changes. Understanding these processes, especially in the context of conservation biology, is urgently needed.

Individual or successiveseed priming with nitric oxide and calcium toward enhancing salt tolerance of wheat crop through early ROS detoxification and activation of antioxidant defense

Despite the considerable efforts reported so far to enhance seed priming, novel ideas are still needed to be suggested to this sustainable sector of agri-seed industry. This could be the first study addressing the effect of nitric oxide (NO) under open field conditions. The impacts of seed redox-priming using sodium nitroprusside (SNP) and osmo-priming with calcium chloride (CaCl2), both applied individually or successively, were investigated under salinity stress conditions on wheat plants (Triticum aestivum L.). Various parameters, including water relations, growth, yield, photosynthetic pigments, and antioxidant activities (enzymatic and non-enzymatic), were recorded to assess the outcomes of these priming agents on mitigating the negative impacts of salinity stress on wheat plants. Water consumptive use (ETa) and irrigation water applied (IWA) decreased with seeds priming. Successive priming with SNP + CaCl2 induced the greatest values of crop water productivity (CWP), irrigation water productivity (IWP), seed index, grain yield and grain nitrogen content.Under salinity stress, the dry weight of plants was decreased. However, hydro-priming and successive chemical priming agents using combinations of calcium chloride and sodium nitroprusside (CaCl2 + SNP & SNP + CaCl2) preserved growth under salinity stress.Individual priming with sodium nitroprusside (SNP) and calcium chloride (CaCl2) resulted in the lowest recorded content of sodium in the shoot, with a value of 2 ppm. On the other hand, successive priming using CaCl2 + SNP or SNP + CaCl2 induced the contents of potassium in the shoot, with values of 40 ppm and 39 ppm, respectively. Malondialdehyde decreased in shoot significantly withapplicationof priming agents. Successive priming with CaCl2 + SNP induced the highest proline contents in shoot (6 µg/ g FW). The highest value of phenolics and total antioxidants contents in shoot were recorded under successive priming using CaCl2 + SNP and SNP + CaCl2.Priming agents improved the activities of ascorbate peroxidase and catalase enzymes. The successive priming improved water relations (ETa, IWA, CWP and IWP) and wheat growth and productivity under salinity stress more than individual priming treatments.

Plant volatile-triggered defense in citrus against biotic stressors.

Plants employ sophisticated defense mechanisms, including releasing volatile organic compounds, to defend against biotic and abiotic stresses. These compounds play a crucial role in plant defense by attracting natural enemies and facilitating communication between plants to activate defense mechanisms. However, there has been no research on how exposure to these compounds activates defense mechanisms in citrus plants. To elucidate the underlying mechanisms governing citrus defensive activation, we conducted a molecular analysis of the rootstock Citrange carrizo [a hybrid of Citrus sinensis × Poncirus trifoliata] in response to defense activation by the volatile (Z)-3-hexenyl propanoate [(Z)-3-HP], utilizing a groundbreaking transcriptomic analysis involving the genomes of both parental species. Our results revealed significant gene expression changes, notably the overexpression of genes related to plant immunity, antioxidant activity, defense against herbivores, and tolerance to abiotic stress. Significantly, P. trifoliata contributed most notably to the hybrid's gene expression profile in response to (Z)-3-HP. Additionally, plants exposed to (Z)-3-HP repelled several citrus pests, attracted natural predators, and led to diminished performance of two key citrus pests. Our study emphasizes the complex molecular basis of volatile-triggered defenses in citrus and highlights the potential of plant volatiles in pest control strategies.

Proteomic Identification and Quantification of Basal Endogenous Proteins in the Ileal Digesta of Growing Pigs.

The accurate estimation of basal endogenous losses (BEL) of amino acids at the ileum is indispensable to improve nutrient utilization efficiency. This study used a quantitative proteomic approach to identify variations in BEL in the ileal digesta of growing pigs fed a nitrogen-free diet (NFD) or a casein diet (CAS). Eight barrow pigs (39.8 ± 6.3 kg initial body weight (BW)) were randomly assigned to a 2 × 2 crossover design. A total of 348 proteins were identified and quantified in both treatments, of which 101 showed a significant differential abundance between the treatments (p < 0.05). Functional and pathway enrichment analyses revealed that the endogenous proteins were associated with intestinal metabolic function. Furthermore, differentially abundant proteins (DAPs) in the digesta of pigs fed the NFD enriched terms and pathways that suggest intestinal inflammation, the activation of innate antimicrobial host defense, an increase in cellular autophagy and epithelial turnover, and reduced synthesis of pancreatic and intestinal secretions. These findings suggest that casein diets may provide a more accurate estimation of BEL because they promote normal gastrointestinal secretions. Overall, proteomic and bioinformatic analyses provided valuable insights into the composition of endogenous proteins in the ileal digesta and their relationship with the functions, processes, and pathways modified by diet composition.

MaHOS15 negatively regulates plant immune defense induced by banana fusarium wilt via salicylic acid pathway

Fusarium wilt of banana (Musa acuminata) poses a significant threat to the banana industry globally. Salicylic acid (SA) serves as a crucial signaling molecule activating the plant's defense response against pathogen infections while also regulating various aspects of plant growth and development. High Expression of Osmotically Responsive Genes 15 (HOS15) acts as a transcriptional corepressor and an E3 ubiquitin ligase complex substrate receptor, playing an important role in regulating biological stress processes. However, the exact immune mechanism of MaHOS15 in the SA signaling pathway remains unclear. In this study, we utilized RT-qPCR, yeast two-hybridization, subcellular localization and allogeneic expression of Arabidopsis to explore MaHOS15's function against banana fusarium wilt. The expression changes of SA pathway-related factors MaNPR3, MaNPR4, MaNPR11, MaTGA8 and MaHOS15 in Foc TR4-resistant and Foc TR4-susceptible bananas infected with Foc TR4 were compared and analyzed. The results showed that the MaHOS15 expression trend in the two cultivars was opposite, while the expression trend of MaNPR4 and MaNPR11 was contrary to that of MaHOS15. Moreover, heterologous overexpression of MaHOS15 in Arabidopsis reduced the variance in SA-related signaling factors. The expression of MaHOS15 increased after defense activation, inhibiting the expression of SA-related immune factors, the immunoregulation of MaHOS15 and SA exhibited contrasting results. Collectively, these findings suggest that MaHOS15 negatively regulates plant immune defenses against banana Fusarium wilt via the salicylic acid pathway, offering potential applications in improving plant resistance to banana Fusarium wilt.

Physiology and fertility of two gull species in relation to plastic additives' exposure

Understanding the impact of plastic and its additives on wild species is crucial as their presence in the environment increases. Polybrominated diphenyl ethers (PBDEs), once used as flame retardants, were restricted due to known toxic effects, but are still detected in the environment. Naturally occurring methoxylated PBDEs (MeO-BDEs) can result from PBDE transformation and may cause similar hazardous effects. Yellow-legged gulls (Larus michahellis, YLG) and Audouin's gulls (Ichthyaetus audouinii, AG) are highly susceptible to plastic additives, due to their distribution, trophic position, and behaviour. In this study, we assessed PBDEs and MeO-BDEs uptake in different tissues and their effects on physiological and reproductive parameters. Findings indicate that, apart from annual differences, adult AG accumulated more MeO-BDEs than YLG in a natural breeding habitat (Deserta), while the latter had lower PBDE levels than YLG breeding in the city of Porto. In relation to chicks, only YLG from Deserta showed higher PBDE concentrations than AG chicks. Individual analysis of each physiological parameter revealed impacts only for adult YLG from Deserta, with neurofunction and immune system inhibition at higher MeO-BDE concentrations. For chicks, AG showed impaired neurofunction, while YLG chicks from Porto exhibited potential genotoxicity effects triggered by higher MeO-BDE levels. Overall health analysis showed activation of antioxidant defences and compromised immune system in YLG adults from Porto due to high values of PBDEs, while chicks from Deserta exhibited inflammation and oxidative stress with high concentrations of MeO-BDEs in the same species. Fertility parameters showed significant differences for sperm counts though suggesting individuals may be able to compensate any exposure effects. This study confirms the widespread presence of plastic-associated compounds and their harmful effects on gulls, particularly on neurofunction, immune system, oxidative balance and fertility, especially due to the presence of MeO-BDEs.

The effectiveness of encapsulated salicylic acid as a treatment to enhance abiotic stress tolerance stems from maintaining proper hormonal homeostasis.

Climate change induces significant abiotic stresses that adversely affect crop yields. One promising solution to improve plant resilience under adverse conditions is the application of exogenous salicylic acid (SA). However, its negative effects on growth and development are a concern. Encapsulation with protective materials like amorphous silica and chitosan has demonstrated a controlled release of SA, minimizing the detrimental impacts. In this work, we elucidate the physiological mechanisms behind this protective mechanism. We employed in vitro cultivation of Arabidopsis, comparing plant responses to both free and encapsulated SA under conditions of salt or mannitol stress, combined or not with high temperature (30°C). Plants treated with encapsulated SA displayed an enhanced tolerance to these stresses that was due, at least in part, to the maintenance of physiological endogenous SA levels, which in turn regulate indole-3-acetic acid (IAA) homeostasis. The activity of the Arabidopsis "DR5::GFP" reporter line supported this finding. Unlike plants treated with free SA (with altered DR5 activity under stress), those treated with encapsulated SA maintained similar activity levels to control plants. Moreover, stressed plants treated with free SA overexpressed genes involved in the SA biosynthesis pathway, leading to increased SA accumulation in roots and rosettes. In contrast, plants treated with encapsulated SA under stress did not exhibit increased expression of EDS1, PAL1, and NPR1 in roots, or of PAL1, PBS3, and NPR1 in rosettes. This indicates that these plants likely experienced lower stress levels, possibly because the encapsulated SA provided sufficient defense activation without triggering pleiotropic effects.

Root-associated Streptomyces produce galbonolides to modulate plant immunity and promote rhizosphere colonization.

The rhizosphere, which serves as the primary interface between plant roots and the soil, constitutes an ecological niche for a huge diversity of microbial communities. Currently, there is little knowledge on the nature and the function of the different metabolites released by rhizospheric microbes to facilitate colonization of this highly competitive environment. Here, we demonstrate how the production of galbonolides, a group of polyene macrolides that inhibit plant and fungal inositol phosphorylceramide synthase (IPCS), empowers the rhizospheric Streptomyces strain AgN23, to thrive in the rhizosphere by triggering the plant's defence mechanisms. Metabolomic analysis of AgN23-inoculated Arabidopsis roots revealed a strong induction in the production of an indole alkaloid, camalexin, which is a major phytoalexin in Arabidopsis. By using a plant mutant compromized in camalexin synthesis, we show that camalexin production is necessary for the successful colonization of the rhizosphere by AgN23. Conversely, hindering galbonolides biosynthesis in AgN23 knock-out mutant resulted in loss of inhibition of IPCS, a deficiency in plant defence activation, notably the production of camalexin, and a strongly reduced development of the mutant bacteria in the rhizosphere. Together, our results identified galbonolides as important metabolites mediating rhizosphere colonization by Streptomyces.

Over-accumulation of chloroplast-nucleus located WHIRLY1 in barley leads to a decrease in growth and an enhanced stress resistance.

WHIRLY1 is a chloroplast-nucleus located DNA/RNA-binding protein with functions in development and stress tolerance. By overexpression of HvWHIRLY1 in barley, one line with a 10-fold and two lines with a 50-fold accumulation of the protein were obtained. In these lines, the relative abundance of the nuclear form exceeded that of the chloroplast form. Growth of the plants was shown to be compromised in a WHIRLY1 abundance-dependent manner. Over-accumulation of WHIRLY1 in chloroplasts had neither an evident impact on nucleoid morphology nor on the composition of the photosynthetic apparatus. Nevertheless, oeW1 plants were found to be compromised in the light reactions of photosynthesis as well as in carbon fixation. The reduction in growth and photosynthesis was shown to be accompanied by a decrease in the levels of cytokinins and an increase in the level of jasmonic acid. Gene expression analyses revealed that in nonstress conditions the oeW1 plants had enhanced levels of pathogen response (PR) gene expression indicating activation of constitutive defense. During growth in continuous light of high irradiance PR gene expression increased indicating that under stress conditions oeW1 are capable to further enhance defense.

Unveiling protein elicitor MoHrip2: A potent biocontrol agent extracted from Magnaporthe oryzae safeguards Australian tobacco (Nicotiana benthamiana) against tobacco aphid (Myzus nicotianae)

The tobacco aphid (Myzus nicotianae) poses a significant threat to global Australian tobacco (Nicotiana benthamiana) output by inflicting damage through leaf twisting and feeding during its early growth stages. To explore potential herbivore resistance in N. benthamiana, this study investigates the effects of the elicitor protein MoHrip2, derived from Magnaporthe oryzae, on the immature growth, survival, and lifespan of M. nicotianae. Compared to the control group, MoHrip2 treatments at three concentrations (85.24, 51.14, 25.57 μg/mL) reduced M. nicotianae population after 7 days, 14 days, and 21 days. All concentrations significantly reduced aphid colonization rate, except for the lowest elicitor concertation (25.57 μg/mL at 7D). Likewise compared to the control group, the highest concentration of MoHrip2 i.e. 85.24 μg/mL, resulted in a decrease in the growth rates of M. nicotianae (second and third-generation). M. nicotianae colonized control plants quicker than MoHrip2-treated N. benthamiana plants in a host selection test. MoHrip2 (85.24, 51.14, 25.57 μg/mL) concentrations extended M. nicotianae nymphal development. The trichomes and wax on MoHrip2-treated leaves made M. nicotianae environment hostile. M. nicotianae reproduction and colonization were reduced by MoHrip2's leaf surface changes. Electrical penetration graphs (EPGs) against M. nicotianae assessed adult reproductive efficiency and pest-pathogen interaction. MoHrip2-treated N. benthamiana seedlings exhibited increased amounts of expression of genes involved in jasmonic acid (JA), salicylic acid (SA) pathways indicating the activation of systemic defense against M. nicotianae. This study reveals a direct correlation between temperature variations and climatic shifts in N. benthamiana plants, highlighting the potential of MoHrip2 in revolutionizing agroecosystems through enhanced pest management and biocontrol strategies. In conclusion, the present study sheds new light on the potential of MoHrip2, derived from M. oryzae, as an effective biocontrol technique against M. nicotianae, infesting N. benthamiana. These findings provide valuable insights into developing innovative and sustainable solutions for pest management in agricultural practices, considering the evidence presented against M. nicotianae, it can be concluded that implementing integrated pest management and utilizing MoHrip2 for bio control in the agroecosystem is an appropriate approach.

GLR-dependent calcium and electrical signals are not coupled to systemic, oxylipin-based wound-induced gene expression in Marchantia polymorpha.

In angiosperms, wound-derived signals travel through the vasculature to systemically activate defence responses throughout the plant. In Arabidopsis thaliana, activity of vasculature-specific Clade 3 glutamate receptor-like (GLR) channels is required for the transmission of electrical signals and cytosolic Ca2+ ([Ca2+]cyt) waves from wounded leaves to distal tissues, triggering activation of oxylipin-dependent defences. Whether nonvascular plants mount systemic responses upon wounding remains unknown. To explore the evolution of systemic defence responses, we investigated electrical and calcium signalling in the nonvascular plant Marchantia polymorpha. We found that electrical signals and [Ca2+]cyt waves are generated in response to mechanical wounding and propagated to nondamaged distal tissues in M. polymorpha. Functional analysis of MpGLR, the only GLR encoded in the genome of M. polymorpha, indicates that its activity is necessary for the systemic transmission of wound-induced electrical signals and [Ca2+]cyt waves, similar to vascular plants. However, spread of these signals is neither coupled to systemic accumulation of oxylipins nor to a transcriptional defence response in the distal tissues of wounded M. polymorpha plants. Our results suggest that lack of vasculature prevents translocation of additional signalling factors that, together with electrical signals and [Ca2+]cyt waves, contribute to systemic activation of defences in tracheophytes.

Proteolysis in plant immunity.

Compared with transcription and translation, protein degradation machineries can act faster and be targeted to different subcellular compartments, enabling immediate regulation of signaling events. It is therefore not surprising that proteolysis has been used extensively to control homeostasis of key regulators in different biological processes and pathways. Over the past decades, numerous studies have shown that proteolysis, where proteins are broken down to peptides or amino acids through ubiquitin-mediated degradation systems and proteases, is a key regulatory mechanism to control plant immunity output. Here, we briefly summarize the roles various proteases play during defence activation, focusing on recent findings. We also update the latest progress of ubiquitin-mediated degradation systems in modulating immunity by targeting plant membrane-localized pattern recognition receptors, intracellular nucleotide-binding domain leucine-rich repeat receptors, and downstream signaling components. Additionally, we highlight recent studies showcasing the importance of proteolysis in maintaining broad-spectrum resistance without obvious yield reduction, opening new directions for engineering elite crops that are resistant to a wide range of pathogens with high yield.

Biochemical and Molecular Basis of Chemically Induced Defense Activation in Maize against Banded Leaf and Sheath Blight Disease.

Maize is the third most vital global cereal, playing a key role in the world economy and plant genetics research. Despite its leadership in production, maize faces a severe threat from banded leaf and sheath blight, necessitating the urgent development of eco-friendly management strategies. This study aimed to understand the resistance mechanisms against banded leaf and sheath blight (BLSB) in maize hybrid "Vivek QPM-9". Seven fungicides at recommended doses (1000 and 500 ppm) and two plant defense inducers, salicylic acid (SA) and jasmonic acid (JA) at concentrations of 50 and 100 ppm, were applied. Fungicides, notably Azoxystrobin and Trifloxystrobin + Tebuconazole, demonstrated superior efficacy against BLSB, while Pencycuron showed limited effectiveness. Field-sprayed Azoxystrobin exhibited the lowest BLSB infection, correlating with heightened antioxidant enzyme activity (SOD, CAT, POX, β-1,3-glucanase, PPO, PAL), similar to the Validamycin-treated plants. The expression of defense-related genes after seed priming with SA and JA was assessed via qRT-PCR. Lower SA concentrations down-regulated SOD, PPO, and APX genes but up-regulated CAT and β-1,3-glucanase genes. JA at lower doses up-regulated CAT and APX genes, while higher doses up-regulated PPO and β-1,3-glucanase genes; SOD gene expression was suppressed at both JA doses. This investigation elucidates the effectiveness of certain fungicides and plant defense inducers in mitigating BLSB in maize hybrids and sheds light on the intricate gene expression mechanisms governing defense responses against this pathogen.

Co-overexpression of SWEET sucrose transporters modulates sucrose synthesis and defence responses to enhance immunity against bacterial blight in rice.

Enhancing carbohydrate export from source to sink tissues is considered to be a realistic approach for improving photosynthetic efficiency and crop yield. The rice sucrose transporters OsSUT1, OsSWEET11aand OsSWEET14 contribute to sucrose phloem loading and seed filling. Crucially, Xanthomonas oryzae pv. oryzae (Xoo) infection in rice enhances the expression of OsSWEET11a and OsSWEET14 genes, and causes leaf blight. Here we show that co-overexpression of OsSUT1, OsSWEET11aand OsSWEET14 in rice reduced sucrose synthesis and transport leading to lower growth and yield but reduced susceptibility to Xoo relative to controls. The immunity-related hypersensitive response (HR) was enhanced in the transformed lines as indicated by the increased expression of defence genes, higher salicylic acidcontentand presence of HR lesions on the leaves. The results suggest that the increased expression of OsSWEET11a and OsSWEET14 in rice is perceived as a pathogen (Xoo) attack that triggers HR and results in constitutive activation of plant defences that are related to the signalling pathways of pathogen starvation. These findings provide a mechanistic basis for the trade-off between plant growth and immunity because decreased susceptibility against Xoo compromised plant growth and yield.