No hormone to rule them all: Interactions of plant hormones during the responses of plants to pathogens

Nanoscale‑boron nitride positively alters rhizosphere microbial communities and subsequent cucumber (Cucumis sativa) growth: A metagenomic analysis

Boron (B) deficiency affects over 132 crop species globally, making effective B supplement crucial for enhancing agricultural yield and health. This study explores an innovative application of nanoscale boron nitride (nano-BN) as a sustainable solution for addressing B deficiency in crops. Cucumber seedlings were treated with different contents of nano-BN under greenhouse conditions and both B and N ionic treatments were set as comparisons. Results show that soil application of 10 mg/kg nano-BN achieved a remarkable 15.8 % increase in fresh weight compared to the control. Notably, nano-BN exhibited superior efficiency in providing essential micronutrients without inducing toxicity as compared to traditional ionic B sources. Phytohormone correlation analysis reveals that nano-BN application significantly enhances levels of indole-3-acetic acid (IAA) and cytokinins while reducing abscisic acid (ABA), fostering optimal plant growth conditions. Furthermore, increases in dissolved organic matter (DOM) and dissolved organic carbon (DOC) levels in the rhizosphere improve nutrient availability and promote beneficial microbial activity in the soil as affected by nano-BN. Metagenomics techniques were used to investigate the impact of nano-BN on soil carbon and nitrogen cycling, alongside its effects on the soil microbiome. The upregulation of genes associated with fermentation pathways as affected by nano-BN suggests the enhanced carbon cycling. Additionally, nano-BN upregulated a number of functional genes involved in nitrogen-based processes, leading to a significant increase in microorganisms harboring nitrogen-fixing genes, including Phenylobacterium, Novosphingobium, and Reyranella. Overall, these findings provide valuable insight into the application of nano-BN in agriculture to sustainably increase crop productivity and enhance the efficiency of carbon and nitrogen cycling.

Transcriptome Responses in Medicago sativa (Alfalfa) Associated with Regrowth Process in Different Grazing Intensities

Medicago sativa L. (alfalfa), a perennial legume, is generally regarded as a valuable source of protein for livestock and is subjected to long and repeated grazing in natural pastures. Studying the molecular response mechanism of alfalfa under different grazing treatments is crucial for understanding its adaptive traits and is of great significance for cultivating grazing-tolerant grass. Here, we performed a transcriptomic analysis to investigate changes in the gene expression of M. sativa under three grazing intensities. In total, 4184 differentially expressed genes (DEGs) were identified among the tested grazing intensities. The analysis of gene ontology (GO) revealed that genes were primarily enriched in cells, cellular processes, metabolic processes, and binding. In addition, two pathways, the plant-pathogen interaction pathway and the plant hormone signal pathway, showed significant enrichment in the Kyoto Encyclopedia of Genes and Genomes (KEGG) analysis. Protein kinases and transcription factors associated with hormones and plant immunity were identified. The plant immunity-related genes were more activated under high grazing treatment, while more genes related to regeneration were expressed under light grazing treatment. These results suggest that M. sativa exhibits different strategies to increase resilience and stress resistance under various grazing intensities. Our findings provide important clues and further research directions for understanding the molecular mechanisms of plant responses to grazing.

The Role of Salicylic, Jasmonic Acid and Ethylene in the Development of the Resistance/Susceptibility of Wheat to the SnTox1-Producing Isolate of the Pathogenic Fungus Stagonospora nodorum (Berk.)

The SnTox1 effector is a virulence factor of the fungal pathogen Stagonospora nodorum (Berk.), which interacts with the host susceptibility gene Snn1 in a gene-for-gene manner and causes necrosis on the leaves of sensitive wheat genotypes. It is known that salicylic acid (SA), jasmonic acid (JA) and ethylene are the key phytohormones involved in plant immunity. To date, effectors of various pathogens have been discovered that can manipulate plant hormonal pathways and even use hormone crosstalk to promote disease development. However, the role of SnTox1 in manipulating hormonal pathways has not been studied in detail. We studied the redox status and the expression of twelve genes of hormonal pathways and two MAPK genes in six bread wheat cultivars sensitive and insensitive to SnTox1 with or without treatment by SA, JA and ethephon (ethylene-releasing agent) during infection with the SnTox1-producing isolate S. nodorum 1SP. The results showed that SnTox1 controls the antagonism between the SA and JA/ethylene signaling pathways. The SA pathway was involved in the development of susceptibility, and the JA/ethylene pathways were involved in the development of wheat plants resistance to the Sn1SP isolate in the presence of a SnTox1-Snn1 interaction. SnTox1 hijacked the SA pathway to suppress catalase activity, increase hydrogen peroxide content and induce necrosis formation; it simultaneously suppresses the JA and ethylene hormonal pathways by SA. To do this, SnTox1 reprogrammed the expression of the MAPK genes TaMRK3 and TaMRK6 and the TF genes TaWRKY13, TaEIN3 and TaWRKY53b. This study provides new data on the role of SnTox1 in manipulating hormonal pathways and on the role of SA, JA and ethylene in the pathosystem wheat S. nodorum.

Comparisons of two receptor-MAPK pathways in a single cell-type reveal mechanisms of signalling specificity

Cells harbour numerous receptor pathways to respond to diverse stimuli, yet often share common downstream signalling components. Mitogen-activated protein kinase (MPK) cascades are an example of such common hubs in eukaryotes. How such common hubs faithfully transduce distinct signals within the same cell-type is insufficiently understood, yet of fundamental importance for signal integration and processing in plants. We engineered a unique genetic background allowing direct comparisons of a developmental and an immunity pathway in one cell-type, the Arabidopsis root endodermis. We demonstrate that the two pathways maintain distinct functional and transcriptional outputs despite common MPK activity patterns. Nevertheless, activation of different MPK kinases and MPK classes led to distinct functional readouts, matching observed pathway-specific readouts. On the basis of our comprehensive analysis of core MPK signalling elements, we propose that combinatorial activation within the MPK cascade determines the differential regulation of an endodermal master transcription factor, MYB36, that drives pathway-specific gene activation.

Combined analysis of transcriptomics with metabolomics provides insights into the resistance mechanism in winter jujube using L-Methionine

Black rots lead to great economic losses in winter jujube industry. The objective of this research was to delve into the underlying mechanisms of enhanced resistance of winter jujube fruit to black rot by L-Methionine (Met) treatment. The findings revealed that the application of Met significantly curtailed lesion diameter and decay incidence in winter jujube fruit. The peroxidase (POD) activity in the Met-treated jujubes was 3.06-fold that in the control jujubes after 4 d of treatment. By day 8, the activities of phenylalanine ammonia-lyase (PAL), chitinase (CHI) and β-1,3-glucanase (GLU) in the Met-treated jujubes had surged to their zenith, being 1.39, 1.22, and 1.52 times in the control group, respectively. At the end of storage, the flavonoid and total phenol content remained 1.58 and 1.06 times than that of the control group. Based on metabolomics and transcriptomics analysis, Met treatment upregulated 6 key differentially expressed metabolites (DEMs) (succinic acid, trans-ferulic acid, salicylic acid, delphinium pigments, (S)-abscisic acid, and hesperidin-7-neohesperidin), 12 key differentially expressed genes (DEGs) (PAL, CYP73A, COMT, 4CL, CAD, POD, UGT72E, ANS, CHS, IAA, TCH4 and PR1), which were involved in phenylpropanoid biosynthesis pathway, flavonoid biosynthesis pathway and plant hormone signal transduction pathway. Further analysis revealed that the most of the enzymes, DEMs and DEGs in this study were associated with both antioxidant and disease resistance. Consequently, Met treatment enhanced disease resistance of winter jujube fruit by elevating antioxidant capacity and triggering defense response. This study might provide theoretical support for utilizing Met in the management and prevention of post-harvest black rot in winter jujube.

Antifungal Activity and Mechanism of Physcion against Sclerotium rolfsii, the Causal Agent of Peanut Southern Blight

Peanut southern blight, caused by the soil-borne pathogen Sclerotium rolfsii, is a widespread and devastating epidemic. Frequently, it is laborious to effectively control by labor-intensive foliar sprays of agrochemicals due to untimely find. In the present study, seed treatment with physcion (PHY) at doses of 0.08, 0.16, and 0.32 g AI kg-1 seed significantly improved the growth and photosynthetic activity of peanuts. Furthermore, PHY seed treatment resulted in an elevated enzymatic activity of key enzymes in peanut roots, including peroxidase, superoxide dismutase, polyphenol oxidase, catalase, lipoxygenase, and phenylalanine ammonia-lyase, as well as an increase in callus accumulation and lignin synthesis at the infection site, ultimately enhancing the root activity. This study revealed that PHY seed treatment could promote the accumulation of reactive oxygen species, salicylic acid (SA), and jasmonic acid (JA)/ethylene (ET) in peanut roots, while also decreasing the content of malondialdehyde levels in response to S. rolfsii infection. The results were further confirmed by transcriptome data and metabolomics. These findings suggest that PHY seed treatment activates the plant defense pathways mediated by SA and JA/ET in peanut roots, enhancing the resistance of peanut plants to S. rolfsii. In short, PHY is expected to be developed into a new plant-derived immunostimulant or fungicide to increase the options and means for peanut disease control.

Pepper immunity against Ralstonia solanacearum is positively regulated by CaWRKY3 through modulation of different WRKY transcription factors

BACKGROUND

Several WRKY transcription factors (TFs), including CaWRKY6, CaWRKY22, CaWRKY27, and CaWRKY40 are known to govern the resistance of pepper (Capsicum annuum L.) plants to Ralstonia solanacearum infestation (RSI) and other abiotic stresses. However, the molecular mechanisms underlying these processes remain elusive.

METHODS

This study functionally described CaWRKY3 for its role in pepper immunity against RSI. The roles of phytohormones in mediating the expression levels of CaWRKY3 were investigated by subjecting pepper plants to 1 mM salicylic acid (SA), 100 µM methyl jasmonate (MeJA), and 100 µM ethylene (ETH) at 4-leaf stage. A virus-induced gene silencing (VIGS) approach based on the Tobacco Rattle Virus (TRV) was used to silence CaWRKY3 in pepper, and transiently over-expressed to infer its role against RSI.

RESULTS

Phytohormones and RSI increased CaWRKY3 transcription. The transcriptions of defense-associated marker genes, including CaNPR1, CaPR1, CaDEF1, and CaHIR1 were decreased in VIGS experiment, which made pepper less resistant to RSI. Significant hypersensitive (HR)-like cell death, H2O2 buildup, and transcriptional up-regulation of immunological marker genes were noticed in pepper when CaWRKY3 was transiently overexpressed. Transcriptional activity of CaWRKY3 was increased with overexpression of CaWRKY6, CaWRKY22, CaWRKY27, and CaWRKY40, and vice versa. In contrast, Pseudomonas syringae pv tomato DC3000 (Pst DC3000) was easily repelled by the innate immune system of transgenic Arabidopsis thaliana that overexpressed CaWRKY3. The transcriptions of defense-related marker genes like AtPR1, AtPR2, and AtNPR1 were increased in CaWRKY3-overexpressing transgenic A. thaliana plants.

CONCLUSION

It is concluded that CaWRKY3 favorably regulates phytohormone-mediated synergistic signaling, which controls cell death in plant and immunity of pepper plant against bacterial infections.

Salivary Protein Cyclin-Dependent Kinase-like from Grain Aphid Sitobion avenae Suppresses Wheat Defense Response and Enhances Aphid Adaptation

Aphids are insect pests that suck phloem sap and introduce salivary proteins into plant tissues through saliva secretion. The effector of salivary proteins plays a key role in the modulation of host plant defense responses and enhancing aphid host adaptation. Based on previous transcriptome sequencing results, a candidate effector cyclin-dependent kinase-like (CDK) was identified from the grain aphid Sitobion avenae. In this study, the function of SaCDK in wheat defense response and the adaptation of S. avenae was investigated. Our results showed that the transient overexpression of SaCDK in tobacco Nicotiana benthamiana suppressed cell death triggered by mouse pro-apoptotic protein-BAX or Phytophthora infestans PAMP-INF1. SaCDK, delivered into wheat cells through a Pseudomonas fluorescens-mediated bacterial type III secretion system, suppressed callose deposition in wheat seedlings, and the overexpression of SaCDK in wheat significantly decreased the expression levels of salicylic acid and jasmonic acid signaling pathway-related genes phenylalanine ammonia lyase (PAL), pathogenesis-related 1 protein (PR1), lipoxygenase (LOX) and Ω-3 fatty acid desaturase (FAD). In addition, aphid bioassay results showed that the survival and fecundity of S. avenae were significantly increased while feeding on the wheat plants carrying SaCDK. Taken together, our findings demonstrate that the salivary protein SaCDK is involved in inhibiting host defense response and improving its host adaptation, which lays the foundation to uncover the mechanism of the interaction of cereal aphids and host plants.

Recent Advances in Dissecting the Function of Ethylene in Interaction between Host and Pathogen

Pathogens influence the growth and development of plants, resulting in detrimental damage to their yields and quality. Ethylene, a gaseous phytohormone, serves a pivotal function in modulating diverse physiological processes in plants, including defense mechanisms against pathogen invasion. Ethylene biosynthesis is involved in both plants and pathogens. Recent empirical research elucidates the intricate interactions and regulatory mechanisms between ethylene and pathogens across various plant species. In this review, we provide a comprehensive overview of the latest findings concerning ethylene's role and its regulatory networks in host-pathogen interactions. Additionally, we explore the crosstalk between ethylene and other phytohormones. Points regarding ethylene emission and its modulation by pathogens are also emphasized. Moreover, we also discuss potential unresolved issues in the field that warrant further investigation.

Signalling responses in the bark and foliage of canker-susceptible and -resistant cypress clones inoculated with Seiridium cardinale

The necrotrophic fungus Seiridium cardinale is the main responsible for Cypress Canker Disease (CCD), a pandemic affecting many Cupressaceae worldwide. The present study aims to elucidate the signalling of the early responses in the bark and foliage of CCD-susceptible and -resistant C. sempervirens clones to S. cardinale inoculation (SI and RI, respectively). In the bark of SI, a peaking production of ethylene (Et) and jasmonic acid (JA) occurred at 3 and 4 days post inoculation (dpi), respectively, suggesting an attempted plant response to the pathogen. A response that, however, was ineffective, as confirmed by the severe accumulation of malondialdehyde by-products at 13 dpi (i.e., lipid peroxidation). Differently, Et emission peaked in RI bark at 3 and 13 dpi, whereas abscisic acid (ABA) accumulated at 1, 4 and 13 dpi, resulting in a lower MDA accumulation (and unchanged levels of antioxidant capacity). In the foliage of SI, Et was produced at 1 and 9 dpi, whereas JA and salicylic acid (SA) accumulated at 1 and 3 dpi. Conversely, an increase of ABA and SA occurred at 1 dpi in the RI foliage. This outcome indicates that some of the observed metabolic alterations, mainly occurring as local defence mechanisms, might be able to gradually shift to a systemic resistance, although an accumulation of MDA was observed in both SI and RI foliage (but with an increased antioxidant capacity reported only in the resistant clone). We believe that the results reported here will be useful for the selection of clones able to limit the spread and damage of CCD.

Genome-wide analysis of the peanut CaM/CML gene family reveals that the AhCML69 gene is associated with resistance to Ralstonia solanacearum

BACKGROUND

Calmodulins (CaMs)/CaM-like proteins (CMLs) are crucial Ca2+-binding sensors that can decode and transduce Ca2+ signals during plant development and in response to various stimuli. The CaM/CML gene family has been characterized in many plant species, but this family has not yet been characterized and analyzed in peanut, especially for its functions in response to Ralstonia solanacearum. In this study, we performed a genome-wide analysis to analyze the CaM/CML genes and their functions in resistance to R. solanacearum.

RESULTS

Here, 67, 72, and 214 CaM/CML genes were identified from Arachis duranensis, Arachis ipaensis, and Arachis hypogaea, respectively. The genes were divided into nine subgroups (Groups I-IX) with relatively conserved exon‒intron structures and motif compositions. Gene duplication, which included whole-genome duplication, tandem repeats, scattered repeats, and unconnected repeats, produced approximately 81 pairs of homologous genes in the AhCaM/CML gene family. Allopolyploidization was the main reason for the greater number of AhCaM/CML members. The nonsynonymous (Ka) versus synonymous (Ks) substitution rates (less than 1.0) suggested that all homologous pairs underwent intensive purifying selection pressure during evolution. AhCML69 was constitutively expressed in different tissues of peanut plants and was involved in the response to R. solanacearum infection. The AhCML69 protein was localized in the cytoplasm and nucleus. Transient overexpression of AhCML69 in tobacco leaves increased resistance to R. solanacearum infection and induced the expression of defense-related genes, suggesting that AhCML69 is a positive regulator of disease resistance.

CONCLUSIONS

This study provides the first comprehensive analysis of the AhCaM/CML gene family and potential genetic resources for the molecular design and breeding of peanut bacterial wilt resistance.

The Targeted Regulation of BDUbc and BDSKL1 Enhances Resistance to Blight in Bambusa pervariabilis × Dendrocalamopsis grandis

Arthrinium phaeospermum is the major pathogen responsible for the significant stem disease "blight" in B. pervariabilis × D. grandis. The interacting proteins of the key pathogenic factor ApCtf1β, BDUbc and BDSKL1, have previously been obtained by two-hybrid, BiFC, GST pull-down yeast assays. However, the functions of these interacting proteins remain unknown. This study successfully obtained transgenic plants overexpressing BDUbc, BDSKL1, and BDUbc + BDSKL1 via Agrobacterium-mediated gene overexpression. qRT-PCR analysis revealed significantly increased expression levels of BDUbc and BDSKL1 in the transgenic plants. After infection with the pathogenic spore suspension, the disease incidence and severity index significantly decreased across all three transgenic plants, accompanied by a marked increase in defense enzyme levels. Notably, the co-transformed plant, OE-BDUbc + BDSKL1, demonstrated the lowest disease incidence and severity index among the transgenic variants. These results not only indicate that BDUbc and BDSKL1 are disease-resistant genes, but also that these two genes may exhibit a synergistic enhancement effect, which further improves the resistance to blight in Bambusa pervariabilis × Dendrocalamopsis grandis.

Innate functions of natural products: A promising path for the identification of novel therapeutics

In the course of evolution, living organisms have become well equipped with diverse natural products that serve important functions, including defence from biotic and abiotic stress, growth regulation, reproduction, metabolism, and epigenetic regulation. It seems to be the organism's ecological niche that influences the natural product's structural and functional diversity. Indeed, natural products constitute the nuts and bolts of molecular co-evolution and ecological relationships among different life forms. Since natural products in the form of specialized secondary metabolites exhibit biological functions via interactions with specific target proteins, they can provide a simultaneous glimpse of both new therapeutics and therapeutic targets in humans as well. In this review, we have discussed the innate role of natural products in the ecosystem and how this intrinsic role provides a futuristic opportunity to identify new drugs and therapeutic targets rapidly.

WRKY transcription factors in plant defense

Environmental stressors caused by climate change are fundamental barriers to agricultural sustainability. Enhancing the stress resilience of crops is a key strategy in achieving global food security. Plants perceive adverse environmental conditions and initiate signaling pathways to activate precise responses that contribute to their survival. WRKY transcription factors (TFs) are essential players in several signaling cascades and regulatory networks that have crucial implications for defense responses in plants. This review summarizes advances in research concerning how WRKY TFs mediate various signaling cascades and metabolic adjustments as well as how epigenetic modifications involved in environmental stress responses in plants can modulate WRKYs and/or their downstream genes. Emerging research shows that clustered regularly interspaced short palindromic repeats (CRISPR)/CRISPR-associated protein (Cas)-mediated genome editing of WRKYs could be used to improve crop resilience.

Hormonal and proteomic analyses of southern blight disease caused by Athelia rolfsii and root chitosan priming on Cannabis sativa in an in vitro hydroponic system

Southern blight disease, caused by the fungal pathogen Athelia rolfsii, suppresses plant growth and reduces product yield in Cannabis sativa agriculture. Mechanisms of pathology of this soil-borne disease remain poorly understood, with disease management strategies reliant upon broad-spectrum antifungal use. Exposure to chitosan, a natural elicitor, has been proposed as an alternative method to control diverse fungal diseases in an eco-friendly manner. In this study, C. sativa plants were grown in the Root-TRAPR system, a transparent hydroponic growth device, where plant roots were primed with .2% colloidal chitosan prior to A. rolfsii inoculation. Both chitosan-primed and unprimed inoculated plants displayed classical symptoms of wilting and yellowish leaves, indicating successful infection. Non-primed infected plants showed increased shoot defense responses with doubling of peroxidase and chitinase activities. The levels of growth and defense hormones including auxin, cytokinin, and jasmonic acid were increased 2-5-fold. In chitosan-primed infected plants, shoot peroxidase activity and phytohormone levels were decreased 1.5-4-fold relative to the unprimed infected plants. When compared with shoots, roots were less impacted by A. rolfsii infection, but the pathogen secreted cell wall-degrading enzymes into the root-growth solution. Chitosan priming inhibited root growth, with root lengths of chitosan-primed plants approximately 65% shorter than the control, but activated root defense responses, with root peroxidase activity increased 2.7-fold along with increased secretion of defense proteins. The results suggest that chitosan could be an alternative platform to manage southern blight disease in C. sativa cultivation; however, further optimization is required to maximize effectiveness of chitosan.

Functions of Plant Phytochrome Signaling Pathways in Adaptation to Diverse Stresses

Phytochromes are receptors for red light (R)/far-red light (FR), which are not only involved in regulating the growth and development of plants but also in mediated resistance to various stresses. Studies have revealed that phytochrome signaling pathways play a crucial role in enabling plants to cope with abiotic stresses such as high/low temperatures, drought, high-intensity light, and salinity. Phytochromes and their components in light signaling pathways can also respond to biotic stresses caused by insect pests and microbial pathogens, thereby inducing plant resistance against them. Given that, this paper reviews recent advances in understanding the mechanisms of action of phytochromes in plant resistance to adversity and discusses the importance of modulating the genes involved in phytochrome signaling pathways to coordinate plant growth, development, and stress responses.

Mechanisms of systemic resistance to pathogen infection in plants and their potential application in forestry

BACKGROUND

The complex systemic responses of tree species to fight pathogen infection necessitate attention due to the potential for yield protection in forestry.

RESULTS

In this paper, both the localized and systemic responses of model plants, such as Arabidopsis and tobacco, are reviewed. These responses were compared to information available that investigates similar responses in woody plant species and their key differences were highlighted. In addition, tree-specific responses that have been documented were summarised, with the critical responses still relying on certain systemic acquired resistance pathways. Importantly, coniferous species have been shown to utilise phenolic compounds in their immune responses. Here we also highlight the lack of focus on systemic induced susceptibility in trees, which can be important to forest health.

CONCLUSIONS

This review highlights the possible mechanisms of systemic response to infection in woody plant species, their potential applications, and where research may be best focused in future.

From Nature to Lab: A Review of Secondary Metabolite Biosynthetic Pathways, Environmental Influences, and In Vitro Approaches

Secondary metabolites are gaining an increasing importance in various industries, such as pharmaceuticals, dyes, and food, as is the need for reliable and efficient methods of procuring these compounds. To develop sustainable and cost-effective approaches, a comprehensive understanding of the biosynthetic pathways and the factors influencing secondary metabolite production is essential. These compounds are a unique type of natural product which recognizes the oxidative damage caused by stresses, thereby activating the defence mechanism in plants. Various methods have been developed to enhance the production of secondary metabolites in plants. The elicitor-induced in vitro culture technique is considered an efficient tool for studying and improving the production of secondary metabolites in plants. In the present review, we have documented various biosynthetic pathways and the role of secondary metabolites under diverse environmental stresses. Furthermore, a practical strategy for obtaining consistent and abundant secondary metabolite production via various elicitation agents used in culturing techniques is also mentioned. By elucidating the intricate interplay of regulatory factors, this review paves the way for future advancements in sustainable and efficient production methods for high-value secondary metabolites.

Signaling Cross-Talk between Salicylic and Gentisic Acid in the 'Candidatus Phytoplasma Solani' Interaction with Sangiovese Vines

"Bois noir" disease associated with 'Candidatus Phytoplasma solani' seriously compromises the production and survival of grapevines (Vitis vinifera L.) in Europe. Understanding the plant response to phytoplasmas should help to improve disease control strategies. Using a combined metabolomic and transcriptomic analysis, this work, therefore, investigated the phytoplasma-grapevine interaction in red cultivar Sangiovese in a vineyard over four seasonal growth stages (from late spring to late summer), comparing leaves from healthy and infected grapevines (symptomatic and symptomless). We found an accumulation of both conjugate and free salicylic acids (SAs) in the leaves of 'Ca. P. solani'-positive plants from early stages of infection, when plants are still asymptomatic. A strong accumulation of gentisic acid (GA) associated with symptoms progression was found for the first time. A detailed analysis of phenylpropanoids revealed a significant accumulation of hydroxycinnamic acids, flavonols, flavan 3-ols, and anthocyanin cyanidin 3-O-glucoside, which are extensively studied due to their involvement in the plant response to various pathogens. Metabolomic data corroborated by gene expression analysis indicated that phenylpropanoid biosynthetic and salicylic acid-responsive genes were upregulated in 'Ca. P. solani-positive plants compared to -negative ones during the observed period.

Multifunctionality of Jasmonic Acid Accumulation during Aphid Infestation in Altering the Plant Physiological Traits That Suppress the Plant Defenses in Wheat Cultivar XN979

Crop plants have coevolved phytohormone-mediated defenses to combat and/or repel their colonizers. The present study determined the effects of jasmonic acid (JA) accumulation during aphid infestation on the preference and performance of Sitobion miscanthi Takahashi (Hemiptera: Aphididae), and its potential role in fine-tuning hormone-dependent responses in XN979 wheat cultivar seedlings was evaluated via the transcriptional profiles of marker genes related to JA- and salicylic acid (SA)-dependent responses. The preference experiment and the life table data reveal that direct foliage spraying of 2.5 mM methyl jasmonate (MeJA) exhibited weak negative or positive effects on the preferential selection and the population dynamics and oviposition parameters of S. miscanthi. The transcription level of phytohormone biosynthesis genes shows that foliage spraying of MeJA significantly upregulated the marker genes in the JA biosynthesis pathway while downregulating the SA pathway. In addition, either MeJA treatment or previous aphid infestation significantly induced upregulated transcription of the genes involved in the JA- and SA-dependent defense responses, and the transcription level of the tryptophan decarboxylase (TaTDC) gene, which facilitates the conversion of L-tryptophan to tryptamine, was rapidly upregulated after the treatments as well. The main products of tryptamine conversion could play a crucial role in suppressing SA-dependent defense responses. These results will provide more experimental evidence to enable understanding of the antagonistic interaction between hormone signaling processes in cereals under aphid infestation.

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.

Effects of chitin and chitosan on root growth, biochemical defense response and exudate proteome of Cannabis sativa

Fungal pathogens pose a major threat to Cannabis sativa production, requiring safe and effective management procedures to control disease. Chitin and chitosan are natural molecules that elicit plant defense responses. Investigation of their effects on C. sativa will advance understanding of plant responses towards elicitors and provide a potential pathway to enhance plant resistance against diseases. Plants were grown in the in vitro Root-TRAPR system and treated with colloidal chitin and chitosan. Plant morphology was monitored, then plant tissues and exudates were collected for enzymatic activity assays, phytohormone quantification, qPCR analysis and proteomics profiling. Chitosan treatments showed increased total chitinase activity and expression of pathogenesis-related (PR) genes by 3-5 times in the root tissues. In the exudates, total peroxidase and chitinase activities and levels of defense proteins such as PR protein 1 and endochitinase 2 were increased. Shoot development was unaffected, but root development was inhibited after chitosan exposure. In contrast, chitin treatments had no significant impact on any defense parameters, including enzymatic activities, hormone quantities, gene expression levels and root secreted proteins. These results indicate that colloidal chitosan, significantly enhancing defense responses in C. sativa root system, could be used as a potential elicitor, particularly in hydroponic scenarios to manage crop diseases.

A unique resistance mechanism is associated with RBgh2 barley powdery mildew adult plant resistance

KEY MESSAGE

Gene expression at the RBgh2 locus indicates involvement in cAMP/G-protein-coupled signalling and innate immunity in barley powdery mildew adult plant resistance. Barley powdery mildew is a globally significant disease, responsible for reduced grain yield and quality. A major effect adult plant resistance gene, RBgh2, was previously found in a landrace from Azerbaijan. The atypical phenotype suggested different underlying genetic factors compared to conventional resistance genes and to investigate this, genome-wide gene expression was compared between sets of heterogeneous doubled haploids. RBgh2 resistance is recessive and induces both temporary genome-wide gene expression changes during powdery mildew infection together with constitutive changes, principally at the RBgh2 locus. Defence-related genes significantly induced included homologues of genes associated with innate immunity and pathogen recognition. Intriguingly, RBgh2 resistance does not appear to be dependent on salicylic acid signalling, a key pathway in plant resistance to biotrophs. Constitutive co-expression of resistance gene homologues was evident at the 7HS RBgh2 locus, while no expression was evident for a 6-transmembrane gene, predicted in silico to contain both G-protein- and calmodulin-binding domains. The gene was disrupted at the 5' end, and G-protein-binding activity was suppressed. RBgh2 appears to operate through a unique mechanism that co-opts elements of innate immunity.

Differences in the transcriptional immune response to Albugo candida between white rust resistant and susceptible cultivars in Brassica rapa L

Albugo candida causing white rust disease decreases the yield of Brassica rapa vegetables greatly. Resistant and susceptible cultivars in B. rapa vegetables have different immune responses against A. candida inoculation, however, the mechanism of how host plants respond to A. candida is still unknown. Using RNA-sequencing, we identified differentially expressed genes (DEGs) between A. candida inoculated [48 and 72 h after inoculation (HAI)] and non-inoculated samples in resistant and susceptible cultivars of komatsuna (B. rapa var. perviridis). Functional DEGs differed between the resistant and susceptible cultivars in A. candida inoculated samples. Salicylic acid (SA) responsive genes tended to be changed in their expression levels by A. candida inoculation in both resistant and susceptible cultivars, but different genes were identified in the two cultivars. SA-dependent systemic acquired resistance (SAR) involving genes were upregulated following A. candida inoculation in the resistant cultivar. Particular genes categorized as SAR that changed expression levels overlapped between A. candida and Fusarium oxysporum f. sp. conglutinans inoculated samples in resistant cultivar, suggesting a role for SAR in defense response to both pathogens particularly in the effector-triggered immunity downstream pathway. These findings will be useful for understanding white rust resistance mechanisms in B. rapa.

PIF8-WRKY42-mediated salicylic acid synthesis modulates red light induced powdery mildew resistance in oriental melon

Light signals and plant hormones are involved in regulating the growth, development and stress resistance of plants; however, it remains unclear whether light affects hormones and thus pathogen resistance in oriental melon. Here, we found that red light promoted salicylic acid (SA) accumulation and powdery mildew resistance by activating the transcription of CmICS, the key gene for SA biosynthesis, and silencing CmICS seriously weakened the induction effect of red light on powdery mildew resistance in oriental melon leaves. Further studies showed that red light induced the expression of CmWRKY42 under powdery mildew stress, and CmWRKY42 directly bound to the CmICS promoter to activate its expression and promote the accumulation of SA under red light. Furthermore, we found that PHYTOCHROME INTERACTING FACTOR 8 (PIF8), as a negative regulator of SA biosynthesis, inhibits CmWRKY42 transcriptional activation by binding to the CmWRKY42 promoter, and thus inhibits transcriptional activation of CmICS by CmWRKY42. Also, CmPIF8 binds to the CmICS promoter and directly inhibits its transcription. In conclusion, our study revealed a new molecular mechanism of the relationship between red light-SA-powdery mildew resistance and provided a theoretical basis for resistance breeding of oriental melon.

Current status and future prospect of managing lead (Pb) stress through microbes for sustainable agriculture

Soil is an important residence under various biotic and abiotic conditions. Contamination of soil by various means has hazardous effects on both plants and humans. Soil contamination by heavy metals occurs due to various man-made activities, including improper industrial and agricultural practices. Among the heavy metals, after arsenic, lead (Pb) was found to be the second most toxic metal and potent pollutants that accumulate in sediments and soils. Pb is not considered an essential element for promoting plant growth but is readily absorbed and accumulated in different plant parts. Many parameters such as pH, root exudation, soil particle size, cation exchange capacity, and other physicochemical parameters are involved in Pb uptake in plants. Excess amounts of Pb pose a threat to plant growth and cause toxicity such as chlorosis, blackening of the root system, and stunted growth. Pb toxicity may inhibit photosynthesis, disturb water balance and mineral nutrition, and alter the hormonal status, structure, and membrane permeability of plants. Therefore, this review addresses the effects of Pb toxicity and its impact on plant growth, including the morphological, physiological, and biological effects of Pb toxicity, the mechanisms behind different strategies promoting plant growth, and in combating Pb-induced stress. The bioremediation strategy for Pb removal from Pb-contaminated soil also plays an important role in combating Pb toxicity using bacterial community. Pb-contaminated soil may be remediated using different technologies such as rhizofiltration and phytoremediation, which tend to have a great capacity to curb Pb-contamination within the soil.

Plant Protection against Viruses: An Integrated Review of Plant Immunity Agents

Plant viruses are an important class of pathogens that seriously affect plant growth and harm crop production. Viruses are simple in structure but complex in mutation and have thus always posed a continuous threat to agricultural development. Low resistance and eco-friendliness are important features of green pesticides. Plant immunity agents can enhance the resilience of the immune system by activating plants to regulate their metabolism. Therefore, plant immune agents are of great importance in pesticide science. In this paper, we review plant immunity agents, such as ningnanmycin, vanisulfane, dufulin, cytosinpeptidemycin, and oligosaccharins, and their antiviral molecular mechanisms and discuss the antiviral applications and development of plant immunity agents. Plant immunity agents can trigger defense responses and confer disease resistance to plants, and the development trends and application prospects of plant immunity agents in plant protection are analyzed in depth.

Quantitative disease resistance: Multifaceted players in plant defense

In contrast to large-effect qualitative disease resistance, quantitative disease resistance (QDR) exhibits partial and generally durable resistance and has been extensively utilized in crop breeding. The molecular mechanisms underlying QDR remain largely unknown but considerable progress has been made in this area in recent years. In this review, we summarize the genes that have been associated with plant QDR and their biological functions. Many QDR genes belong to the canonical resistance gene categories with predicted functions in pathogen perception, signal transduction, phytohormone homeostasis, metabolite transport and biosynthesis, and epigenetic regulation. However, other "atypical" QDR genes are predicted to be involved in processes that are not commonly associated with disease resistance, such as vesicle trafficking, molecular chaperones, and others. This diversity of function for QDR genes contrasts with qualitative resistance, which is often based on the actions of nucleotide-binding leucine-rich repeat (NLR) resistance proteins. An understanding of the diversity of QDR mechanisms and of which mechanisms are effective against which classes of pathogens will enable the more effective deployment of QDR to produce more durably resistant, resilient crops.

Ozone-Induced Biochemical and Molecular Changes in Vitis vinifera Leaves and Responses to Botrytis cinerea Infections

To investigate how plants cope with multi-stress conditions, we analyzed the biochemical and molecular changes of Vitis vinifera leaves subjected to single or sequential double stresses (infection by Botrytis cinerea (Bc) and ozone (O₃, 100 ppb for 3 h) treatment). In Bc⁺/O₃^- leaves, the hydrogen peroxide (H₂O₂) induction (observed at 12 and 24 h from the end of treatment (FET)) triggered a production of ethylene (Et; +35% compared with Bc^-/O₃^- leaves), which was preceded by an increase of salicylic acid (SA; +45%). This result confirms a crosstalk between SA- and Et-related signaling pathways in lesion spread. The ozone induced an early synthesis of Et followed by jasmonic acid (JA) and SA production (about 2-fold higher), where Et and SA signaling triggered reactive oxygen species production by establishing a feedback loop, and JA attenuated this cycle by reducing Et biosynthesis. In Bc⁺ + O₃⁺ leaves, Et peaked at 6 and 12 h FET, before SA confirmed a crosstalk between Et- and SA-related signaling pathways in lesion propagation. In O₃⁺ + Bc⁺ leaves, the H₂O₂ induction triggered an accumulation of JA and Et, demonstrating a synergistic action in the regulation of defence reactions. The divergence in these profiles suggests a rather complex network of events in the transcriptional regulation of genes involved in the systemic acquired resistance.

Plant Hormonomics: A Key Tool for Deep Physiological Phenotyping to Improve Crop Productivity

Agriculture is particularly vulnerable to climate change. To cope with the risks posed by climate-related stressors to agricultural production, global population growth, and changes in food preferences, it is imperative to develop new climate-smart crop varieties with increased yield and environmental resilience. Molecular genetics and genomic analyses have revealed that allelic variations in genes involved in phytohormone-mediated growth regulation have greatly improved productivity in major crops. Plant science has remarkably advanced our understanding of the molecular basis of various phytohormone-mediated events in plant life. These findings provide essential information for improving the productivity of crops growing in changing climates. In this review, we highlight the recent advances in plant hormonomics (multiple phytohormone profiling) and discuss its application to crop improvement. We present plant hormonomics as a key tool for deep physiological phenotyping, focusing on representative plant growth regulators associated with the improvement of crop productivity. Specifically, we review advanced methodologies in plant hormonomics, highlighting mass spectrometry- and nanosensor-based plant hormone profiling techniques. We also discuss the applications of plant hormonomics in crop improvement through breeding and agricultural management practices.

Analysis of metabolic and transcription levels provides insights into the interactions of plant hormones and crosstalk with MAPKs in the early signaling response of cherry tomato fruit induced by the yeast cell wall

Yeast cell walls (YCW) are promising bio-based elicitors for controlling post-harvest fruit decay. In this study, 1% YCW induction increased the resistance of cherry tomato fruits, reducing disease incidence by 66%. This study aimed to explore the interaction of hormones and crosstalk with MAPKs (mitogen-activated protein kinases) in the early response of resistance regulation in cherry tomato fruits treated with YCW and U0126. We analyzed the temporal changes in hormone content, the expression of critical genes involved in phytohormone biosynthesis, and signal transduction in cherry tomato fruits response to the induction. Results revealed that jasmonic acid (JA) and brassinosteroids (BR) significantly regulated early resistance response in fruit induced by 1% YCW. The salicylic acid (SA) pathway is inhibited by the activation of the JA pathway. JA and SA signaling pathway crosstalk with the MAPK3 pathway. BR plays an essential role in the regulation of fruit resistance. The BR pathway may function independently when JA/SA and MAPK3 pathways are inhibited.

A comprehensive dynamic immune acetylproteomics profiling induced by Puccinia polysora in maize

Lysine-ε-acetylation (Kac) is a reversible post-translational modification that plays important roles during plant-pathogen interactions. Some pathogens can deliver secreted effectors encoding acetyltransferases or deacetylases into host cell to directly modify acetylation of host proteins. However, the function of these acetylated host proteins in plant-pathogen defense remains to be determined. Employing high-resolution tandem mass spectrometry, we analyzed protein abundance and lysine acetylation changes in maize infected with Puccinia polysora (P. polysora) at 0 h, 12 h, 24 h, 48 h and 72 h. A total of 7412 Kac sites from 4697 proteins were identified, and 1732 Kac sites from 1006 proteins were quantified. Analyzed the features of lysine acetylation, we found that Kac is ubiquitous in cellular compartments and preferentially targets lysine residues in the -F/W/Y-X-X-K (ac)-N/S/T/P/Y/G- motif of the protein, this Kac motif contained proteins enriched in basic metabolism and defense-associated pathways during fungal infection. Further analysis of acetylproteomics data indicated that maize regulates cellular processes in response to P. polysora infection by altering Kac levels of histones and non-histones. In addition, acetylation of pathogen defense-related proteins presented converse patterns in signaling transduction, defense response, cell wall fortification, ROS scavenging, redox reaction and proteostasis. Our results provide informative resources for studying protein acetylation in plant-pathogen interactions, not only greatly extending the understanding on the roles of acetylation in vivo, but also providing a comprehensive dynamic pattern of Kac modifications in the process of plant immune response.

Ambivalent response in pathogen defense: A double-edged sword?

Plants possess effective immune systems that defend against most microbial attackers. Recent plant immunity research has focused on the classic binary defense model involving the pivotal role of small-molecule hormones in regulating the plant defense signaling network. Although most of our current understanding comes from studies that relied on information derived from a limited number of pathosystems, newer studies concerning the incredibly diverse interactions between plants and microbes are providing additional insights into other novel mechanisms. Here, we review the roles of both classical and more recently identified components of defense signaling pathways and stress hormones in regulating the ambivalence effect during responses to diverse pathogens. Because of their different lifestyles, effective defense against biotrophic pathogens normally leads to increased susceptibility to necrotrophs, and vice versa. Given these opposing forces, the plant potentially faces a trade-off when it mounts resistance to a specific pathogen, a phenomenon referred to here as the ambivalence effect. We also highlight a novel mechanism by which translational control of the proteins involved in the ambivalence effect can be used to engineer durable and broad-spectrum disease resistance, regardless of the lifestyle of the invading pathogen.

Identification of candidate genes associated with resistance against race 0 of Colletotrichum lentis in Lens ervoides

Resistance to anthracnose caused by the fungal pathogen Colletotrichum lentis was explored through transcriptome sequencing over a period of 24 to 96 h post-inoculation (hpi) of the partially resistant recombinant inbred lines (RIL) LR-66-528 and susceptible LR-66-524 of the crop wild relative Lens ervoides population LR-66. The development of infection vesicles and primary hyphae by C. lentis were significantly higher on susceptible RIL LR-66-524 compared to partially resistant LR-66-528 at 24 and 48 hpi, but exponential trends in fungal growth were observed between 24 to 96 hpi in both RILs. Comparison of inoculated with mock-inoculated samples revealed 3091 disease responsive genes, among which 477 were differentially expressed between the two RILs. These were clustered into six expression clusters with genes that had either high or low expression in one of the RILs. Differentially expressed genes (DEGs) were functionally annotated and included genes coding LRR and NB-ARC domain disease resistance proteins, protein detoxification, LRR receptor-like kinase family proteins, and wall-associated Ser/Thr Kinases. DEGs were compared to genes in previously published anthracnose resistance QTLs mapped in LR-66 and revealed 22 DEGs located in 3 QTLs. Expression of 21 DEGs was validated using RT-qPCR confirming expression trends in RNA-seq.

Plant-soil-microbes: A tripartite interaction for nutrient acquisition and better plant growth for sustainable agricultural practices

Plants can achieve their proper growth and development with the help of microorganisms associated with them. Plant-associated microbes convert the unavailable nutrients to available form and make them useful for plants. Besides nutrient acquisition, soil microbes also inhibit the pathogens that cause harm to plant growth and induces defense response. Due to the beneficial activities of soil nutrient-microbe-plant interactions, it is necessary to study more on this topic and develop microbial inoculant technology in the agricultural field for better crop improvement. The soil microbes can be engineered, and plant growth-promoting rhizobacteria (PGPR) and plant growth-promoting bacteria (PGPB) technology can be developed as well, as its application can be improved for utilization as biofertilizer, biopesticides, etc., instead of using harmful chemical biofertilizers. Moreover, plant growth-promoting microbe inoculants can enhance crop productivity. Although, scientists have discussed several tools and techniques by omics and gene editing approaches for crop improvement to avoid biotic and abiotic stress and make the plant healthier and more nutritive. However, beneficial soil microbes that help plants with the nutrient acquisition, development, and stress resistance were ignored, and farmers started utilizing chemical fertilizers. Thus, this review attempts to summarize the interaction system of plant microbes, the role of beneficiary soil microbes in the rhizosphere zone, and their role in plant health promotion, particularly in the nutrition acquisition of the plant. The review will also provide a better understanding of soil microbes that can be exploited as biofertilizers and plant growth promoters in the field to create environmentally friendly, sustainable agriculture systems.

Current understanding of plant-microbe interaction through the lenses of multi-omics approaches and their benefits in sustainable agriculture

The success of sustainable agricultural practices has now become heavily dependent on the interactions between crop plants and their associated microbiome. Continuous advancement in high throughput sequencing platforms, omics-based approaches, and gene editing technologies has remarkably accelerated this area of research. It has enabled us to characterize the interactions of plants with associated microbial communities more comprehensively and accurately. Furthermore, the genomic and post-genomic era has significantly refined our perspective toward the complex mechanisms involved in those interactions, opening new avenues for efficiently deploying the knowledge in developing sustainable agricultural practices. This review focuses on our fundamental understanding of plant-microbe interactions and the contribution of existing multi-omics approaches, including those under active development and their tremendous success in unraveling different aspects of the complex network between plant hosts and microbes. In addition, we have also discussed the importance of sustainable and eco-friendly agriculture and the associated outstanding challenges ahead.

The Improved Biocontrol Agent, F1-35, Protects Watermelon against Fusarium Wilt by Triggering Jasmonic Acid and Ethylene Pathways

Watermelon Fusarium wilt, caused by Fusarium oxysporum f. sp. niveum (FON), is one of the most important diseases, and has become a major limiting factor to watermelon production worldwide. Previous research has found that the improved biocontrol agent, F1-35, had a high control efficiency to watermelon Fusarium wilt. In this study, the control efficiency of F1-35 to watermelon Fusarium wilt was firstly tested, and the control efficiency was 61.7%. Then, we investigated the mode of action of F1-35 in controlling watermelon Fusarium wilt. Using a pairing assay, we found that F1-35 did not inhibit the normal growth of FON. To know more about the interaction between F1-35 and watermelon root, the protein expressions of roots after 12, 24, and 48 h post-inoculation were examined. A total of 1109 differentially expressed proteins were obtained. KEGG analysis found that the most differentially expressed proteins occurred in alpha-linolenic acid metabolism, cysteine and methionine metabolism, plant–pathogen interaction, and the MAPK signaling pathway to the plant. A further analysis of differentially expressed proteins showed that F1-35 triggered the jasmonic acid and ethylene pathways in watermelon. To validate our results, the qRT-PCR was used to analyze the gene expression levels of PAL, LOX1, and CTR1. The gene expression results showed that those genes, which were positive correlated with the JA pathway, were up-expressed, including PAL and LOX1, and the negative associated gene, CTR1, was down-expressed. In conclusion, the improved biocontrol agent, F1-35, improves the resistance of watermelons to FON by triggering the JA and ET pathways.

Comparative transcriptome analysis revealed molecular mechanisms of peanut leaves responding to Ralstonia solanacearum and its type III secretion system mutant

Bacterial wilt caused by Ralstonia solanacearum is a serious soil-borne disease that limits peanut production and quality, but the molecular mechanisms of the peanut response to R. solanacearum remain unclear. In this study, we reported the first work analyzing the transcriptomic changes of the resistant and susceptible peanut leaves infected with R. solanacearum HA4-1 and its type III secretion system mutant strains by the cutting leaf method at different timepoints (0, 24, 36, and 72 h post inoculation). A total of 125,978 differentially expressed genes (DEGs) were identified and subsequently classified into six groups to analyze, including resistance-response genes, susceptibility-response genes, PAMPs induced resistance-response genes, PAMPs induced susceptibility-response genes, T3Es induced resistance-response genes, and T3Es induced susceptibility-response genes. KEGG enrichment analyses of these DEGs showed that plant-pathogen interaction, plant hormone signal transduction, and MAPK signaling pathway were the outstanding pathways. Further analysis revealed that CMLs/CDPKs-WRKY module, MEKK1-MKK2-MPK3 cascade, and auxin signaling played important roles in the peanut response to R. solanacearum. Upon R. solanacearum infection (RSI), three early molecular events were possibly induced in peanuts, including Ca²⁺ activating CMLs/CDPKs-WRKY module to regulate the expression of resistance/susceptibility-related genes, auxin signaling was induced by AUX/IAA-ARF module to activate auxin-responsive genes that contribute to susceptibility, and MEKK1-MKK2-MPK3-WRKYs was activated by phosphorylation to induce the expression of resistance/susceptibility-related genes. Our research provides new ideas and abundant data resources to elucidate the molecular mechanism of the peanut response to R. solanacearum and to further improve the bacterial wilt resistance of peanuts.

Nanosensor Applications in Plant Science

Plant science is a major research topic addressing some of the most important global challenges we face today, including energy and food security. Plant science has a role in the production of staple foods and materials, as well as roles in genetics research, environmental management, and the synthesis of high-value compounds such as pharmaceuticals or raw materials for energy production. Nanosensors-selective transducers with a characteristic dimension that is nanometre in scale-have emerged as important tools for monitoring biological processes such as plant signalling pathways and metabolism in ways that are non-destructive, minimally invasive, and capable of real-time analysis. A variety of nanosensors have been used to study different biological processes; for example, optical nanosensors based on Förster resonance energy transfer (FRET) have been used to study protein interactions, cell contents, and biophysical parameters, and electrochemical nanosensors have been used to detect redox reactions in plants. Nanosensor applications in plants include nutrient determination, disease assessment, and the detection of proteins, hormones, and other biological substances. The combination of nanosensor technology and plant sciences has the potential to be a powerful alliance and could support the successful delivery of the 2030 Sustainable Development Goals. However, a lack of knowledge regarding the health effects of nanomaterials and the high costs of some of the raw materials required has lessened their commercial impact.

Comparative transcriptome analysis of rice cultivars resistant and susceptible to Rhizoctonia solani AG1-IA

BACKGROUND

Rice sheath blight, which is caused by Rhizoctonia solani, is the most destructive disease affecting rice production, but the resistance mechanism to this pathogen has not been fully elucidated.

RESULTS

In this study, we selected two rice cultivars based on their resistance to the pathogen and analyzed and compared the transcriptomic profiles of two cultivars, the moderately resistant variety Gangyuan8 and the highly susceptible variety Yanfeng47, at different time points after inoculation. The comparative transcriptome profiling showed that the expression of related genes gradually increased after pathogen inoculation. The number of differentially expressed genes (DEGs) in Yanfeng47 was higher than that in Gangyuan8, and this result revealed that Yanfeng47 was more susceptible to fungal attack. At the early stage (24 and 48 h), the accumulation of resistance genes and a resistance metabolism occurred earlier in Ganguan8 than in Yanfeng47, and the resistance enrichment entries were more abundant in Ganguan8 than in Yanfeng47.

CONCLUSIONS

Based on the GO and KEGG enrichment analyses at five infection stages, we concluded that phenylalanine metabolism and the jasmonic acid pathway play a crucial role in the resistance of rice to sheath blight. Through a comparative transcriptome analysis, we preliminarily analyzed the molecular mechanism responsible for resistance to sheath blight in rice, and the results lay the foundation for the development of gene mining and functional research on rice resistance to sheath blight.

Bacterial cyclodipeptides elicit Arabidopsis thaliana immune responses reducing the pathogenic effects of Pseudomonas aeruginosa PAO1 strains on plant development

Plants being sessile organisms are exposed to various biotic and abiotic factors, thus causing stress. The Pseudomonas aeruginosa bacterium is an opportunistic pathogen for animals, insects, and plants. Direct exposure of Arabidopsis thaliana to the P. aeruginosa PAO1 strain induces plant death by producing a wide variety of virulence factors, which are regulated mainly by quorum sensing systems. Besides virulence factors, P. aeruginosa PAO1 also produces cyclodipeptides (CDPs), which possess auxin-like activity and promote plant growth through activation of the target of the rapamycin (AtTOR) pathway. On the other hand, plant defense mechanisms are regulated through the production of phytohormones, such as salicylic acid (SA) and jasmonic acid (JA), which are induced in response to pathogen-associated molecular patterns (PAMPs), activating defense genes associated with SA and JA such as PATHOGENESIS-RELATED-1 (PR-1) and LIPOXYGENASE2 (LOX2), respectively. PR proteins are suggested to play critical roles in coordinating the Systemic Acquired Resistance (SAR). In contrast, LOX proteins (LOX2, LOX3, and LOX4) have been associated with the production of JA by producing its precursors, oxylipins. The activation of defense mechanisms involves signaling cascades such as Mitogen-Activated Protein Kinases (MAPKs) or the TOR pathway as a switch for re-directing energy towards defense or growth. In this work, we challenged A. thaliana (wild type, mpk6 or mpk3 mutants, and overexpressing TOR) seedlings with P. aeruginosa PAO1 strains to identify the role of bacterial CDPs in the plant immune response. Results showed that the pre-exposure of these Arabidopsis seedlings to CDPs significantly reduced plant infection of the pathogenic P. aeruginosa PAO1 strains, indicating that plants that over-express AtTOR or lack MPK3/MPK6 protein-kinases are more susceptible to the pathogenic effects. In addition, CDPs induced the GUS activity only in the LOX2::GUS plants, indicative of JA-signaling activation. Our findings indicate that the CDPs are molecules that trigger SA-independent and JA-dependent defense responses in A. thaliana; hence, bacterial CDPs may be considered elicitors of the Arabidopsis immune response to pathogens.

Impact of Future Elevated Carbon Dioxide on C3 Plant Resistance to Biotic Stresses

Before the end of the century, atmospheric carbon dioxide levels are predicted to increase to approximately 900 ppm. This will dramatically affect plant physiology and influence environmental interactions and, in particular, plant resistance to biotic stresses. This review is a broad survey of the current research on the effects of elevated CO₂ (eCO₂) on phytohormone-mediated resistance of C₃ agricultural crops and related model species to pathogens and insect herbivores. In general, while plants grown in eCO₂ often have increased constitutive and induced salicylic acid levels and suppressed induced jasmonate levels, there are exceptions that implicate other environmental factors, such as light and nitrogen fertilization in modulating these responses. Therefore, this review sets the stage for future studies to delve into understanding the mechanistic basis behind how eCO₂ will affect plant defensive phytohormone signaling pathways under future predicted environmental conditions that could threaten global food security to inform the best agricultural management practices.[Formula: see text] Copyright © 2022 The Author(s). This is an open access article distributed under the CC BY-NC-ND 4.0 International license.

Transcriptomic and proteomic analyses of Cucurbita ficifolia Bouché (Cucurbitaceae) response to Fusarium oxysporum f.sp. cucumerium

Background

Fusarium oxysporum f. sp. cucumerinum (FOC) is the causal agent of cucumber Fusarium wilt, which can cause extensive damages and productivity losses. Cucurbita ficifolia Bouché (Cucurbitaceae) is usually used as rootstock for cucumber because of its excellent resistance to Fusarium wilt. Our previous study found that C.ficifolia has high FOC resistance, the underlying mechanism of which is unclear.

Results

Transcriptome and proteome profiling was performed on the basis of RNA-Seq and isobaric tag for relative and absolute quantitation technology to explore the molecular mechanisms of the response of Cucurbita ficifolia Bouché to Fusarium oxysporum f. sp. cucumerium infection. Comparative analyses revealed that 1850 genes and 356 protein species were differentially regulated at 2d and 4d after FOC inoculation. However, correlation analysis revealed that only 11 and 39 genes were differentially regulated at both the transcriptome and proteome levels after FOC inoculation at 2d and 4d, respectively. After FOC inoculation, plant hormones signal transduction, transcription factors were stimulated, whereas wax biosynthesis and photosynthesis were suppressed. Increased synthesis of oxidative-redox proteins is involved in resistance to FOC.

Conclusions

This study is the first to reveal the response of C. ficifolia leaf to FOC infection at the transcriptome and proteome levels, and to show that FOC infection activates plant hormone signaling and transcription factors while suppressing wax biosynthesis and photosynthesis. The accumulation of oxidative-redox proteins also plays an important role in the resistance of C. ficifolia to FOC. Results provide new information regarding the processes of C. ficifolia leaf resistance to FOC and will contribute to the breeding of cucumber rootstock with FOC resistance.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12864-022-08674-7.

Integrative omics approaches revealed a crosstalk among phytohormones during tuberous root development in cassava

Integrative omics approaches revealed a crosstalk among phytohormones during tuberous root development in cassava. Tuberous root formation is a complex process consisting of phase changes as well as cell division and elongation for radial growth. We performed an integrated analysis to clarify the relationships among metabolites, phytohormones, and gene transcription during tuberous root formation in cassava (Manihot esculenta Crantz). We also confirmed the effects of the auxin (AUX), cytokinin (CK), abscisic acid (ABA), jasmonic acid (JA), gibberellin (GA), brassinosteroid (BR), salicylic acid, and indole-3-acetic acid conjugated with aspartic acid on tuberous root development. An integrated analysis of metabolites and gene expression indicated the expression levels of several genes encoding enzymes involved in starch biosynthesis and sucrose metabolism are up-regulated during tuberous root development, which is consistent with the accumulation of starch, sugar phosphates, and nucleotides. An integrated analysis of phytohormones and gene transcripts revealed a relationship among AUX signaling, CK signaling, and BR signaling, with AUX, CK, and BR inducing tuberous root development. In contrast, ABA and JA inhibited tuberous root development. These phenomena might represent the differences between stem tubers (e.g., potato) and root tubers (e.g., cassava). On the basis of these results, a phytohormonal regulatory model for tuberous root development was constructed. This model may be useful for future phytohormonal studies involving cassava.

Ascorbate peroxidase 1 confers resistance to southern corn leaf blight in maize

Southern corn leaf blight (SCLB), caused by Bipolaris maydis, is one of the most devastating diseases affecting maize production. However, only one SLCB resistance gene, conferring partial resistance, is currently known, underscoring the importance of isolating new SCLB resistance-related genes. Here, we performed a comparative proteomic analysis and identified 258 proteins showing differential abundance during the maize response to B. maydis. These proteins included an ascorbate peroxidase (Zea mays ascorbate peroxidase 1 (ZmAPX1)) encoded by a gene located within the mapping interval of a previously identified quantitative trait locus associated with SCLB resistance. ZmAPX1 overexpression resulted in lower H₂ O₂ accumulation and enhanced resistance against B. maydis. Jasmonic acid (JA) contents and transcript levels for JA biosynthesis and responsive genes increased in ZmAPX1-overexpressing plants infected with B. maydis, whereas Zmapx1 mutants showed the opposite effects. We further determined that low levels of H₂ O₂ are accompanied by an accumulation of JA that enhances SCLB resistance. These results demonstrate that ZmAPX1 positively regulates SCLB resistance by decreasing H₂ O₂ accumulation and activating the JA-mediated defense signaling pathway. This study identified ZmAPX1 as a potentially useful gene for increasing SCLB resistance. Furthermore, the generated data may be relevant for clarifying the functions of plant APXs.

A new NLR gene for resistance to Tomato spotted wilt virus in tomato (Solanum lycopersicum)

A typical NLR gene, Sl5R-1, which regulates Tomato spotted wilt virus resistance, was fine mapped to a region less than 145 kb in the tomato genome. Tomato spotted wilt is a viral disease caused by Tomato spotted wilt virus (TSWV), which is a devastating disease that affects tomato (Solanum lycopersicum) production worldwide, and the resistance provided by the Sw-5 gene has broken down in some cases. In order to identify additional genes that confer resistance to TSWV, the F₂ population was mapped using susceptible (M82) and resistant (H149) tomato lines. After 3 years of mapping, the main quantitative trait locus on chromosome 05 was narrowed to a genomic region of 145 kb and was subsequently identified by the F₂ population, with 1971 plants in 2020. This region encompassed 14 candidate genes, and in it was found a gene cluster consisting of three genes (Sl5R-1, Sl5R-2, and Sl5R-3) that code for NBS-LRR proteins. The qRT-PCR and virus-induced gene silencing approach results confirmed that Sl5R-1 is a functional resistance gene for TSWV. Analysis of the Sl5R-1 promoter region revealed that there is a SlTGA9 transcription factor binding site caused by a base deletion in resistant plants, and its expression level was significantly up-regulated in infected resistant plants. Analysis of salicylic acid (SA) and jasmonic acid (JA) levels and the expression of SA- and JA-regulated genes suggest that SlTGA9 interacts or positively regulates Sl5R-1 to affect the SA- and JA-signaling pathways to resist TSWV. These results demonstrate that the identified Sl5R-1 gene regulates TSWV resistance by its own promoter interacting with the transcription factor SlTGA9.

The secretome of Verticillium dahliae in collusion with plant defence responses modulates Verticillium wilt symptoms

Verticillium dahliae is a notorious soil‐borne pathogen that enters hosts through the roots and proliferates in the plant water‐conducting elements to cause Verticillium wilt. Historically, Verticillium wilt symptoms have been explained by vascular occlusion, due to the accumulation of mycelia and plant biomacromolecule aggregation, and also by phytotoxicity caused by pathogen‐secreted toxins. Beyond the direct cytotoxicity of some members of the secretome, this review systematically discusses the roles of the V. dahliae secretome in vascular occlusion, including the deposition of polysaccharides as an outcome of plant cell wall destruction, the accumulation of fungal mycelia, and modulation of plant defence responses. By modulating plant defences and hormone levels, the secretome manipulates the vascular environment to induce Verticillium wilt. Thus, the secretome of V. dahliae colludes with plant defence responses to modulate Verticillium wilt symptoms, and thereby bridges the historical concepts of both toxin production by the pathogen and vascular occlusion as the cause of wilting symptoms.

Root-TRAPR: a modular plant growth device to visualize root development and monitor growth parameters, as applied to an elicitor response of Cannabis sativa

BACKGROUND

Plant growth devices, for example, rhizoponics, rhizoboxes, and ecosystem fabrication (EcoFAB), have been developed to facilitate studies of plant root morphology and plant-microbe interactions in controlled laboratory settings. However, several of these designs are suitable only for studying small model plants such as Arabidopsis thaliana and Brachypodium distachyon and therefore require modification to be extended to larger plant species like crop plants. In addition, specific tools and technical skills needed for fabricating these devices may not be available to researchers. Hence, this study aimed to establish an alternative protocol to generate a larger, modular and reusable plant growth device based on different available resources.

RESULTS

Root-TRAPR (Root-Transparent, Reusable, Affordable three-dimensional Printed Rhizo-hydroponic) system was successfully developed. It consists of two main parts, an internal root growth chamber and an external structural frame. The internal root growth chamber comprises a polydimethylsiloxane (PDMS) gasket, microscope slide and acrylic sheet, while the external frame is printed from a three-dimensional (3D) printer and secured with nylon screws. To test the efficiency and applicability of the system, industrial hemp (Cannabis sativa) was grown with or without exposure to chitosan, a well-known plant elicitor used for stimulating plant defense. Plant root morphology was detected in the system, and plant tissues were easily collected and processed to examine plant biological responses. Upon chitosan treatment, chitinase and peroxidase activities increased in root tissues (1.7- and 2.3-fold, respectively) and exudates (7.2- and 21.6-fold, respectively). In addition, root to shoot ratio of phytohormone contents were increased in response to chitosan. Within 2 weeks of observation, hemp plants exhibited dwarf growth in the Root-TRAPR system, easing plant handling and allowing increased replication under limited growing space.

CONCLUSION

The Root-TRAPR system facilitates the exploration of root morphology and root exudate of C. sativa under controlled conditions and at a smaller scale. The device is easy to fabricate and applicable for investigating plant responses toward elicitor challenge. In addition, this fabrication protocol is adaptable to study other plants and can be applied to investigate plant physiology in different biological contexts, such as plant responses against biotic and abiotic stresses.

Simultaneous Electrochemical Sensing of Indole-3-Acetic Acid and Salicylic Acid on Poly(L-Proline) Nanoparticles-Carbon Dots-Multiwalled Carbon Nanotubes Composite-Modified Electrode

Sensitive simultaneous electrochemical sensing of phytohormones indole-3-acetic acid and salicylic acid based on a novel poly(L-Proline) nanoparticles-carbon dots composite consisting of multiwalled carbon nanotubes was reported in this study. The poly(L-Proline) nanoparticles-carbon dots composite was facilely prepared by the hydrothermal method, and L-Proline was used as a monomer and carbon source for the preparation of poly(L-Proline) nanoparticles and carbon dots, respectively. Then, the poly(L-Proline) nanoparticles-carbon dots-multiwalled carbon nanotubes composite was prepared by ultrasonic mixing of poly(L-Proline) nanoparticles-carbon dots composite dispersion and multiwalled carbon nanotubes. Scanning electron microscope, transmission electron microscope, Fourier transform infrared spectroscopy, ultraviolet visible spectroscopy, energy dispersive spectroscopy, cyclic voltammetry, electrochemical impedance spectroscopy, and linear sweep voltammetry were used to characterize the properties of the composite. poly(L-Proline) nanoparticles were found to significantly enhance the conductivity and sensing performance of the composite. Under optimal conditions, the composite-modified electrode exhibited a wide linear range from 0.05 to 25 μM for indole-3-acetic acid and from 0.2 to 60 μM for salicylic acid with detection limits of 0.007 μM and 0.1 μM (S/N = 3), respectively. In addition, the proposed sensor was also applied to simultaneously test indole-3-acetic acid and salicylic acid in real leaf samples with satisfactory recovery.

(+)-Catechin, epicatechin and epigallocatechin gallate are important inducible defensive compounds against Ectropis grisescens in tea plants

The tea plant, Camellia sinensis (L.) O. Kuntze, is an economically important, perennial woody plant rich in catechins. Although catechins have been reported to play an important role in plant defences against microbes, their roles in the defence of tea plants against herbivores remain unknown. In this study, we allowed the larvae of Ectropis grisescens, a leaf-feeding pest, to feed on the plants, and alternatively, we wounded the plants and then treated them with E. grisescens oral secretions (WOS). Both approaches triggered jasmonic acid-, ethylene- and auxin-mediated signalling pathways; as a result, plants accumulated three catechin compounds: (+)-catechin, epicatechin and epigallocatechin. Not only was the mass of E. grisescens larvae fed on plants previously infested with E. grisescens or treated with WOS significantly lower than that of larvae fed on controls, but also artificial diet supplemented with epicatechin, (+)-catechin or epigallocatechin gallate reduced larval growth rates. In addition, the exogenous application of jasmonic acid, ethylene or auxin induced the biosynthesis of the three catechins, which, in turn, enhanced the resistance of tea plants to E. grisescens, leading to the coordination of the three signalling pathways. Our results suggest that the three catechins play an important role in the defences of tea plants against E. grisescens.