Salicylic acid in plant immunity and beyond

LuxR solo regulates recalcitrant aromatic compound biodegradation: Repression and activation of dibenzofuran-catabolic genes expression in a Rhodococcus sp

Aromatic compounds contribute to the category of prevalent, toxic, and persistent pollutants in the environment. Microbial degradation of aromatic pollutants is eco-friendly, which depends on efficient manipulation of catabolic enzyme activity. As homologs of quorum sensing LuxR family regulators, LuxR solos play important roles in cell-cell interaction; however, there are few studies on its regulation of recalcitrant aromatic compounds degradation. In this study, the transcriptional regulatory mechanism of dibenzofuran catabolic genes controlled by LuxR solo was elucidated in the dioxin-degrader Rhodococcus sp. strain p52. LuxR solo encoded by catabolic plasmid pDF01 was detected to bind to the promoters of dfdA and dfdB and inhibit the genes expression, which are involved in dibenzofuran degradation. The repression of the LuxR on the catabolic genes expression was not affected by dibenzofuran, but could be alleviated by the intermediate of dibenzofuran degradation, salicylic acid. RNA-Seq analysis suggested that the LuxR solo related to regulating the expression of multiple key genes on the chromosome and catabolic plasmids pDF02. Phylogenetic analysis indicated that LuxR solos frequently distribute among aromatics-degrading bacteria. This study reveals the molecular regulatory network of dibenzofuran degradation mediated by LuxR solo and deepens the understanding of transcriptional regulatory mechanisms of aromatic compounds degradation.

Type-dependent biostimulant-mediated induction of nutrients and phenolic compounds improved plant tolerance against canola aphids (Brevicoryne brassicae L.)

The canola aphid (Brevicoryne brassicae L.) is a global threat to the production of canola. Field studies on the mechanism of biostimulants-driven plant tolerance against canola aphids are either scare or inconclusive. To assess the potential of biostimulants-salicylic acid (SA) and citric acid (CA)-in conferring induced resistance against canola aphids, two-year field experiments were conducted. The 0, 0.5, and 1 mM concentrations of each biostimulant were compared to an insecticide (Carbosulfan 20 EC) and infested control groups. Aphid abundance decreased by 19.3 % (1 mM SA), 16.3 % (0.5 mM SA), and 15.7 % (1 mM CA), compared to the insecticide treatment. Significant increases were observed in plant height, number of siliques (pods), seeds per silique, thousand-seed weight, seed yield m-2, total yield (kg ha-1), and oil contents. The 1 mM SA led to the highest levels of nitrogen, phosphorous, magnesium, calcium, and zinc, while 1 mM CA had highest concentrations of potassium, iron, and copper. Reverse-phase HPLC (RP-HPLC) separation analyses revealed that 1 mM SA promoted the accumulation of gallic, m-coumaric, p-coumaric, and cinnamic acid, while 1 mM CA induced the synthesis of myricetin, quercetin, syringic, vanillic, caffeic, chlorogenic, ferulic, and sinapic acid. The 0.5 mM concentration of either biostimulant showed intermediate efficacy. Our findings demonstrate that each biostimulant induces a distinct nutrient and phenolic compound in canola likely through a unique defense eliciting mechanism. These insights advances our understanding of the aphid-stress tolerance mechanism in canola to support the breeding of aphid-resistant varieties.

UDP-glycosyltransferase PpUGT74F2 is involved in fruit immunity via modulating salicylic acid metabolism

Flesh fruits are essential for human health, but pathogen infection poses a threat to fruit production and postharvest storage. The hormone salicylic acid (SA) and its metabolites, such as sugar conjugates and methyl salicylate (MeSA), play a crucial role in regulating plant immune responses. However, the UDP-glycosyltransferases (UGTs) responsible for modulating SA metabolism in fruit have yet to be identified, and further investigation is needed to elucidate its involvement in fruit immune response. Here, we identified PpUGT74F2 as an enzyme with the highest transcription level in peach fruit, responsible for catalyzing the biosynthesis of SA glucoside (SAG), but not for MeSAG formation in fruit. Furthermore, infection of peach fruit with Monilinia fructicola, which causes brown rot disease, led to reduced expression of PpUGT74F2, resulting in a significant decrease in SAG content and an increase in MeSA levels. Transgenic tomatoes expressing heterologous PpUGT74F2 increased susceptibility to gray mold. Interestingly, overexpressing PpUGT74F2 did not affect SA levels but dramatically reduced MeSA levels in response to pathogen infection, accompanied by significantly reduced expression of pathogen-related (PR) genes in transgenic tomatoes. This study highlights that PpUGT74F2 acts as a negative regulatory factor for fruit immunity through a distinct mechanism not previously reported in plants.

Phytohormones: Heart of plants' signaling network under biotic, abiotic, and climate change stresses

Industrialization has made the world increasingly unstable, subjecting plants to various constraints. As a consequence, plants are constantly experiencing biological, environmental, and climatic constraints, necessitating defense mechanisms to ensure their survival. Plants are vulnerable to various biotic factors, including insects, pathogens (bacterial, fungal, viral, and nematodes), weeds, and herbivores. They also face different abiotic and climate change challenges such as drought (regulated by genes like GH3, DREB, ZIFL1;3, etc), salinity, heavy metals, metalloids, ultraviolet radiations (UV), ozone (O3), low and high temperature (chilling/cold/freezing/heat), carbon dioxide (CO2), chlorofluorocarbons (CFCs), and flooding/hypoxia/anoxia. Different transcriptional factors, such as KNOX1, PYK10, and NRP1, regulate these abiotic and climate change stresses. Different phytohormones such as auxin (regulated by components AUX/IAA3, PIN, indole-glucosinolate, indole-3-acetaldoxine), gibberellin (key elements involved in the synthesis and signaling such as DELLA, GA3ox, RhHB1), cytokinin (signaling through ARR5), ethylene (involved transcription factors like AP2/ERF), abscisic acid (signaling regulated through SnRK2), salicylic acid, jasmonic acid (regulated by JAZ1/TIFYIOA), brassinosteroids, nitric oxide, and strigolactones (synthetic precursor being GR24) control plants' maturation in normal and stressed conditions by regulating various metabolic and physiological plant activities. Phytohormonal interactions and their synergy are often assessed by different techniques and assays such as CRISPR/Cas9, ELISA, RIA, luciferase, GAL4, and mEmerald GFP. Their synthesis and signaling are regulated by various genes (such as YUCCA1, YUCCA5, GA3ox, etc), transporters (PIN, such as PIN, ABCB, NPF, etc), and receptors (such as PLY4, PLY5, BZR1/BES1, MYC2, etc) and have different precursors such as L-arginine, L-tryptophan, phenylalanine, linolenic acid, S-adenosylmethionine, geranylgeranyl diphosphate. This review comprehensively analyses the breakthrough in phytohormones and their signaling in regulating plants' growth and maturation. Their significance in combating the biotic, abiotic, and climate change stresses, improving stress adaptation to identify novel strategies enhancing plant resilience, sustainable agriculture, and ensuring food security.

Hydrolase P1 in Bacillus velezensis HN-2 confers tobacco resistance by delaying TMV infection

BACKGROUND

Tobacco is a critical cash crop globally, contributing significantly to government revenues. However, its production is severely threatened by tobacco mosaic virus (TMV), which causes substantial yield and quality losses, leading to economic damage. Given the limited efficacy of chemical controls, biological control methods have gained prominence. Bacillus spp. are recognized as effective agents for plant disease management. In prior research, Bacillus velezensis HN-2 demonstrated promising traits for inducing plant resistance.

RESULTS

This study revealed that the total protein extract from B. velezensis HN-2 triggers the production of reactive oxygen species, upregulates antioxidant enzymes, activates immune-related protein genes, and induces systemic resistance in plants. Its effectiveness surpassed that of benzothiadiazole and Dufulin in delaying TMV invasion. Further analysis identified a specific hydrolase protein within the total protein extract that plays a key role in the observed antiviral activity. Exogenous expression and functional assays confirmed that this hydrolase, designated P1, is the primary active protein in B. velezensis HN-2 responsible for delaying TMV infection.

CONCLUSION

Hydrolase protein P1 acts as an elicitor to induce systemic resistance in the tobacco plant against TMV Infection. These findings provide an experimental foundation for the application of B. velezensis HN-2 in biological control strategies and offer theoretical insights into the use of Bacillus-derived proteins for TMV management. © 2025 Society of Chemical Industry.

The Role of Salicylic Acid in Activating Plant Stress Responses-Results of the Past Decade and Future Perspectives

Salicylic acid (SA) is one of the most commonly used natural plant protection compounds, considered one of the most effective in mitigating the damage caused by abiotic and biotic stressors. The current review article summarizes the most significant achievements in stress management over the past ten years. We also provide insights into new perspectives on the use of salicylic acid. The article summarizes the role of SA in signaling, its effects on biotic, abiotic and oxidative stress, evaluates the possibilities of its use in combination with other active compounds, and presents the promising application opportunities offered by new techniques that may become available in the coming decades.

A novel stress-inducible dCas9 system for solanaceous plants

Conditional manipulation of gene expression is essential in plant biology, yet a simple stimuli-based inducible system for regulating any plant gene is lacking. Here, we present an innovative stress-inducible CRISPR/dCas9-based gene-regulatory toolkit tailored for intentional gene regulation in solanaceous plants. We have translationally fused the transmembrane domain of a tomato membrane-bound NAC transcription factor with dCas9 to utilize the reversible-tethering-based activation mechanism. This system sequesters dCas9 to the plasma membrane under normal conditions and allows membrane detachment in response to heat induction and NLS-mediated nuclear transfer, enabling stress-inducible gene regulation. Transient assays with tomato codon-optimized dCas9-assisted inducible CRISPR activation and interference systems confirmed their superior ability on transcriptional control, rapid induction, and reversibility after stimulus withdrawal in solanaceous plants. The transformative potential of the toolkit was exemplified by enhancing tomato immunity against bacterial speck disease under elevated temperatures by precisely regulating crucial salicylic acid signalling components, SlCBP60g and SlSARD1. Additionally, it was instrumental in engineering heat-stress tolerance in tomato plants through multiplex activation of heat-responsive transcription factors, SlNAC2 and SlHSFA6b. These findings demonstrate the unprecedented temporal control offered by this novel stress-inducible toolkit over gene-expression dynamics, paving the way for favourable manipulation of complex traits in environmentally-challenged crops.

Trans-Kingdom RNA Dialogues: miRNA and milRNA Networks as Biotechnological Tools for Sustainable Crop Defense and Pathogen Control

MicroRNAs (miRNAs) are a class of non-coding RNAs approximately 20-24 nucleotides in length, which play a crucial role during gene regulation in plant-pathogen interaction. They negatively regulate the expression of target genes, primarily at the transcriptional or post-transcriptional level, through complementary base pairing with target gene sequences. Recent studies reveal that during pathogen infection, miRNAs produced by plants and miRNA-like RNAs (milRNAs) produced by fungi can regulate the expression of endogenous genes in their respective organisms and undergo trans-kingdom transfer. They can thereby negatively regulate the expression of target genes in recipient cells. These findings provide novel perspectives for deepening our understanding of the regulatory mechanisms underlying plant-pathogen interactions. Here, we summarize and discuss the roles of miRNAs and milRNAs in mediating plant-pathogen interactions via multiple pathways, providing new insights into the functions of these RNAs and their modes of action. Collectively, these insights lay a theoretical foundation for the targeted management of crop diseases.

Isoprene deters insect herbivory by priming plant hormone responses

Isoprene, emitted by some plants, deters insect herbivory. However, the associated biochemical and physiological responses that confer herbivory resistance remain unknown. We used engineered isoprene-emitting (IE) and non-emitting (NE) control tobacco plants to interpret isoprene-mediated defense against herbivory in plants. Hornworm larvae raised on IE plants exhibited stunted growth compared to those raised on NE plants. Worms preferred to feed on NE rather than IE leaves, indicating deterrent effects of isoprene on insect feeding. Worm feeding induced a greater increase in jasmonic acid (JA), a crucial hormone for insect resistance, in IE leaves compared to that in NE leaves. Assimilation rates were stably maintained in IE plants, suggesting a protective role of isoprene in preserving photosynthetic efficiency during insect herbivory. Wound-induced increase in isoprene emission correlated with the elevation of key metabolites of the isoprene biosynthesis pathway. Our results highlight JA-priming functions of isoprene and provide insights into isoprene-mediated defense against insect herbivory.

Choosing the right signaling pathway: hormone responses to Phytophthora cinnamomi during compatible and incompatible interactions with chestnut (Castanea spp.)

Ink disease caused by the hemibiotrophic root pathogen Phytophthora cinnamomi (Pc) is devastating for the European chestnut (Castanea sativa), unlike Asian chestnuts and interspecific hybrids, which are resistant to Pc. The role that hormone responses play for Pc resistance remains little understood, especially regarding the temporal regulation of hormone responses. We explored the relationship between changes in tree health and physiology and alterations in leaf and root phytohormones and primary and secondary metabolites during compatible and incompatible Castanea spp.-Pc interactions. Susceptible (S) C. sativa and resistant (R) C. sativa × C. crenata ramets were inoculated with Pc in roots and assessed for disease progression, leaf physiology and biochemistry at 1, 3, 5 and 8 days after inoculation (d.a.i.). In S chestnuts, Pc increasingly deteriorated the leaf physiological functioning by decreasing leaf CO2 assimilation, stomatal conductance, transpiration rate, chlorophylls content and the maximum quantum yield of the photosystem II over time, triggering aerial symptoms (leaf wilting and chlorosis) 8 d.a.i. Pc had little impact on the leaf physiological functioning of R chestnuts, which remained asymptomatic. In roots of S chestnuts, Pc transiently induced jasmonates signaling (5 d.a.i.) while impairing root carbohydrates metabolism over time. In leaves, a transient antioxidant burst (5 d.a.i.) followed by abscisic acid (ABA) accumulation (8 d.a.i.) was observed. R chestnuts responded to Pc by up-regulating root salicylic acid (SA) at early (1 d.a.i.) and late (8 d.a.i.) infection stages, in an antagonistic crosstalk with root ABA. Overall, the results pinpoint an important role of SA in mediating the resistant response of chestnuts to Pc, but also show that the specific hormone pathways induced by Pc are genotype dependent. The study also highlights that the dynamic nature of hormone responses over time must be considered when elucidating hormone-regulated responses to Pc.

Interaction between pathogenesis-related (PR) proteins and phytohormone signaling pathways in conferring disease tolerance in plants

Pathogenesis-related (PR) proteins are critical defense signaling molecules induced by phytopathogens. They play a vital role in plant's defense signaling pathways and innate immunity, particularly in systemic acquired resistance (SAR) and serve as key molecular markers of plant defense. Overexpressing PR genes, such as chitinase, thaumatin, glucanase, thionin and defensin, either individually or in combination, have significantly boosted plants' defense responses against various pathogens. However, signaling pathways regulating the expression of these versatile proteins remain only partially understood. Plant hormones like salicylic acid (SA) and jasmonic acid (JA) are known for their well-established roles in regulating PR gene responses to pathogens and other stress conditions. PR genes interact with various components of hormonal signaling pathways, including receptors (e.g., NPR1 in SA signaling), transcription factors (e.g., MYC2 in JA signaling), and cis-regulating elements (e.g., W-box), to modulate plant defense responses. Recent studies have highlighted the contributions of different plant hormones to plant immunity and their interactions with PR proteins in a process known as hormonal crosstalk, which helps coordinate immunity activation. This review provides a comprehensive overview of the PR proteins, their complexity, and hormonal crosstalk in immunity, aiming to understand these interactions for improved pathogen resistance.

Structural and Functional Analysis of the Lectin-like Protein Llp1 Secreted by Ustilago maydis upon Infection of Maize

The biotrophic fungus Ustilago maydis, which causes smut disease in maize, secretes numerous proteins upon plant colonization. Some of them, termed effectors, help to evade plant defenses and manipulate cellular processes within the host. The function of many proteins specifically secreted during infection remains elusive. In this study, we biochemically characterized one such protein, UMAG_00027, that is highly expressed during plant infection. We show that UMAG_00027 is a secreted protein with a lectin-like fold and therefore term it Llp1 (lectin-like-protein 1). Llp1 decorated the fungal cell wall of cells grown in axenic culture or proliferating in planta, which is in agreement with its potential sugar-binding ability. We were unable to identify the precise sugar moieties that are bound by Llp1. CRISPR/Cas9-mediated deletion of llp1 reveals that the gene is not essential for fungal virulence. A structural search shows the presence of several other lectin-like proteins in U. maydis that might compensate for the function of Llp1 in ∆llp1 mutants. We therefore speculate that Llp1 is part of a family of lectin-like proteins with redundant functions.

GWSF-EuSWAP70 gene expression to enhance gray mold resistance in Arabidopsis thaliana

BACKGROUND

Eucalyptus, a widely cultivated woody plant, is susceptible to a diverse array of pests and diseases, leading to reduced yields and economic losses. Traditional breeding methods are very time-consuming; therefore, plant genetic engineering has emerged as a promising approach for plant pathogen management. However, the genetic transformation system of eucalyptus is still in its early stages of development, while studies on transgenic eucalyptus and its disease resistance genes are limited. The SWAP70 gene has been shown to play a crucial role in the defense response of Arabidopsis thaliana and rice. In this study, the model plant A. thaliana was selected for genetic transformation. The aim was to enhance the expression of the EuSWAP70 gene derived from Eucalyptus grandis, and other disease resistance genes by utilizing an artificial GWSF promoter.

RESULTS

The results showed that the EuSWAP70 gene was successfully transformed into A. thaliana, and the PCR assay confirmed the presence of the EuSWAP70 gene in transgenic Arabidopsis plants. The gray mold resistance of the EuSWAP70 transgenic Arabidopsis plants under GWSF and CaMV35S promoters was evaluated against Botrytis cinerea infection. After gray mold infection, Arabidopsis plants were ranked by leaf pore area percentage: wildtype > CaMV35S-EuSWAP70 > GWSF-EuSWAP70. The transgenic plants showed stronger gray mold resistance, and the GWSF-EuSWAP70 transgenic plants were stronger than the CaMV35S-EuSWAP70 transgenic plants.

Distinct Infection Mechanisms of Rhizoctonia solani AG-1 IA and AG-4 HG-I+II in Brachypodium distachyon and Barley

Rhizoctonia solani is a basidiomycete phytopathogenic fungus that causes rapid necrosis in a wide range of crop species, leading to substantial agricultural losses worldwide. The species complex is divided into 13 anastomosis groups (AGs) based on hyphal fusion compatibility and further subdivided by culture morphology. While R. solani classifications were shown to be independent of host specificity, it remains unclear whether different R. solani isolates share similar virulence mechanisms. Here, we investigated the infectivity of Japanese R. solani isolates on Brachypodium distachyon and barley. Two isolates, AG-1 IA (from rice) and AG-4 HG-I+II (from cauliflower), infected leaves of both plants, but only AG-4 HG-I+II infected roots. B. distachyon accessions Bd3-1 and Gaz-4 and barley cultivar 'Morex' exhibited enhanced resistance to both isolates compared to B. distachyon Bd21 and barley cultivars 'Haruna Nijo' and 'Golden Promise'. During AG-1 IA infection, but not AG-4 HG-I+II infection, resistant Bd3-1 and Morex induced genes for salicylic acid (SA) and N-hydroxypipecolic acid (NHP) biosynthesis. Pretreatment with SA or NHP conferred resistance to AG-1 IA, but not AG-4 HG-I+II, in susceptible B. distachyon Bd21 and barley Haruna Nijo. On the leaves of susceptible Bd21 and Haruna Nijo, AG-1 IA developed extensive mycelial networks with numerous infection cushions, which are specialized infection structures well-characterized in rice sheath blight. In contrast, AG-4 HG-I+II formed dispersed mycelial masses associated with underlying necrosis. We propose that the R. solani species complex encompasses at least two distinct infection strategies: AG-1 IA exhibits a hemibiotrophic lifestyle, while AG-4 HG-I+II follows a predominantly necrotrophic strategy.

Maize DLR1/NHX7 Is Required for Root Development Under Potassium Deficiency

Root System Architecture (RSA) is a crucial plant trait that governs a plant's ability to absorb water and nutrients. In this study, we describe a mutant with nutrient-dependent defects in root development, affecting both the primary root and lateral roots (LRs). This mutant, identified through a screen for defects in LR development, has been designated dlr1-1. The dlr1-1 mutant exhibits impaired LR emergence rather than defects in the LR primordium (LRP) formation, particularly under potassium (K+)-deprivation conditions. This impairment likely stems from inhibited cell proliferation caused by the dlr1-1 mutation. K+ deprivation specifically leads to the accumulation of salicylic acid (SA) in the dlr1-1 mutant, consistent with the upregulation of SA biosynthesis genes. Moreover, exogenous application of SA to wild-type plants (B73) mimics the dlr1-1 phenotype. Conversely, treatment of the dlr1-1 mutant with 2-aminoindane-2-phosphonic acid, an SA biosynthesis inhibitor, partially restores LR emergence, indicating that elevated SA levels may be responsible for the mutant's developmental defects. MutMap analysis and allelism tests confirmed that the phenotypes of the dlr1-1 mutant results from the loss of the Na+/H+ antiporter, ZmNHX7. Additionally, the application of NaCl exacerbates the dlr1-1 mutant phenotype, suggesting that the root defects in dlr1-1 mutant depend on ion homoeostasis. In conclusion, our findings demonstrate that maize DLR1/NHX7 is essential for root development under potassium deprivation.

Abscisic Acid Can Play a Dual Role in the Triticum aestivum-Stagonospora nodorum Pathosystem

Abscisic acid (ABA) is not only important for plant responses to abiotic stresses, but also plays a key and multifaceted role in plant immunity. In this work, we analyzed the role of ABA in the development of resistance/susceptibility in the wheat (Triticum aestivum L.)-Stagonospora nodorum Berk. pathosystem, which includes the recognition of the necrotic effectors (NEs) of a pathogen by the corresponding wheat susceptibility genes. We studied the interaction of the S. nodorum SnB isolate, which produces two NEs, SnToxA and SnTox3, with three wheat genotypes having different combinations of the corresponding host susceptibility genes (Tsn1 and Snn3-B1). The results of this work on the gene expression and redox status of resistant and sensitive wheat genotypes treated with ABA show that ABA signaling is directed at inducing the resistance of wheat plants to S. nodorum SnB isolate through the activation of the early post-invasive defense genes TaERD15 and TaABI5. The induction of the expression of these genes leads to reactive oxygen species (ROS) accumulation during the early stage of infection, with the subsequent limitation of the pathogen's growth. In the presence of a compatible interaction of SnTox3-Snn3-B1, ABA signaling is suppressed. On the contrary, in the presence of a compatible interaction of SnToxA-Tsn1, ABA signaling is activated, but the activity of the early post-invasive defense genes TaERD15 and TaABI5 is inhibited, and the expression of the NAC (NAM, ATAF1/2, and CUC2) transcription factor (TF) family genes TaNAC29 and TaNAC21/22 is induced. The TF genes TaNAC29 and TaNAC21/22 in the presence of SnToxA induce the development of the susceptibility of wheat plants to S. nodorum SnB, associated with a decrease in the oxidative burst during the early stage of infection. Thus, our study provides new data on the role of the NEs SnTox3 and SnToxA in manipulating ABA signaling in the development of the susceptibility of wheat to S. nodorum. Deepening our knowledge in this area will be instrumental for developing new strategies for breeding programs and will contribute to the development of environmentally friendly sustainable agriculture.

Salicylic Acid Improved the Growth of Dunaliella salina and Increased the Proportion of 9-cis-β-Carotene Isomers

Dunaliella salina is an important source of natural β-carotene (containing 9-cis and all trans isomers) for industrial production. The phytohormone salicylic acid (SA) has been proven to have impacts on the stress resistance of higher plants, but research on microalgae is currently unclear. In this study, the effects of SA on the growth, biochemical composition, antioxidant enzyme activity, key enzymes of β-carotene synthesis, and cis-and trans-isomers of β-carotene in D. salina under different salt concentrations were investigated. The results were shown that at concentrations of 1.5, 2, and 2.5 M NaCl, the antioxidant enzyme activity and key enzymes for β-carotene synthesis in algal cells were significantly increased, but the content and proportion of 9-cis isomer in β-carotene isomers decreased. The addition of SA significantly increased the growth and antioxidant enzyme (SOD, MDA) activity, as well as the synthesis of key enzyme phytoene synthase (PSY), phytoene desaturase (PDS), and lycopene β cyclase (LCYB) of D. salina under high-salinity conditions. It is worth noting that under the treatment of SA, the proportion of 9-cis isomer in the three salt concentrations (1.5, 2, 2.5 M NaCl) significantly increased by 32.09%, 20.30%, and 11.32%, respectively. Moreover, SA can not only improve the salt tolerance of D. salina, but also increase the proportion of 9-cis isomer, with higher physiological activity in β-carotene, thereby enhancing the application value of D. salina.

SYNTAXIN OF PLANTS 132 underpins secretion of cargoes associated with salicylic acid signaling and pathogen defense

Secretory trafficking in plant cells is facilitated by SNARE (soluble N-ethylmaleimide-sensitive factor attachment protein receptor) proteins that drive membrane fusion of cargo-containing vesicles. In Arabidopsis, SYNTAXIN OF PLANTS 132 (SYP132) is an evolutionarily ancient SNARE that functions with syntaxins SYP121 and SYP122 at the plasma membrane. Whereas SYP121 and SYP122 mediate overlapping secretory pathways, albeit with differences in their importance in plant-environment interactions, the SNARE SYP132 is absolutely essential for plant development and survival. SYP132 promotes endocytic traffic of the plasma membrane H+-ATPase AHA1 and aquaporin PIP2;1, and it coordinates plant growth and bacterial pathogen immunity through PATHOGENESIS-RELATED1 (PR1) secretion. Yet, little else is known about SYP132 cargoes. Here, we used advanced quantitative tandem mass tagging (TMT)-MS combined with immunoblot assays to track native secreted cargo proteins in the leaf apoplast. We found that SYP132 supports a basal level of secretion in Arabidopsis leaves, and its overexpression influences salicylic acid and jasmonic acid defense-related cargoes including PR1, PR2, and PR5 proteins. Impairing SYP132 function also suppressed defense-related secretory traffic when challenged with the bacterial pathogen Pseudomonas syringae. Thus, we conclude that, in addition to its role in hormone-related H+-ATPase cycling, SYP132 influences basal plant immunity.

Pesticide-induced metabolic disruptions in crops: A global perspective at the molecular level

Pesticide pollution has emerged as a critical global environmental issue of pervasive concern. Although the application of pesticides has provided substantial benefits in controlling weeds, pests, and crop diseases, their indiscriminate use poses considerable challenges to soil health and food safety. Pesticides can be absorbed by crops through either foliar or root uptake, resulting in deleterious effects such as extensive tissue damage, growth inhibition, and reduced crop quality. Beside these visible effects, pesticides can alter gene expression and disrupt cellular signaling transduction, thereby interfering with essential metabolic processes even inducing toxic stress. Moreover, pesticides can interact intricately with biomolecules (e.g. proteins, nucleic acid) in crops, causing significant alterations in protein structure and physiological function. This review focuses on pesticide residues and their associated toxicity, emphasizing their pervasive influence on vital physiological and metabolic pathways, including carbohydrate metabolism, amino acid metabolism, and fatty acid metabolism. Particular attention is given to elucidating the molecular mechanisms underlying these disturbances, specifically regarding transcriptional regulation, cell signaling pathways, and biomolecular interactions. This review provides a comprehensive understanding of multifaceted effects of pesticides and to underscore the necessity for sustainable agricultural practices to safeguard crop yield and quality.

Phosphoproteomic analysis uncovers phosphorylated proteins in response to salicylic acid and N-hydroxypipecolic acid in Arabidopsis

BACKGROUND

The phytohormone salicylic acid (SA) serves as a crucial signaling molecule within the realm of plant immunity, playing an indispensable role in both local and systemic acquired resistance (SAR). N-hydroxypipecolic acid (NHP), a derivative of L-lysine, is integral to the induction of SAR. Recent investigations have illuminated the intricate manner in which NHP orchestrates the establishment of SAR in conjunction with the immune signal SA.

METHODS AND RESULTS

To further explore the mechanisms governing the synergistic regulation of SAR by SA and NHP, we conducted an extensive phosphoproteomic analysis aimed at identifying the phosphoproteins modulated either commonly or uniquely by SA and NHP, employing a phosphoproteomics platform built upon high-resolution mass spectrometry. Our study revealed a total of 133 phosphopeptides, derived from 115 distinct proteins, exhibiting exclusive responsiveness to NHP treatment. In contrast, 229 phosphopeptides sourced from 204 proteins demonstrated exclusive sensitivity to SA treatment. Additionally, the phosphorylation status of 215 proteins, including numerous kinases, phosphatases, transcription factors, and proteins implicated in membrane trafficking, was commonly modulated by both SA and NHP.

CONCLUSION

This investigation offers detailed insights into the key phosphoproteins influenced either collectively or specifically by SA and NHP, thereby enabling further exploration of the mechanisms underlying the synergistic regulation of immune responses orchestrated by these two potent molecules.

Post-translational modifications control the signal at the crossroads of plant-pathogen interactions

The co-evolution of plants and pathogens has enabled them to 'outsmart' each other by promoting their own defence responses and suppressing those of the other. While plants are reliant on their sophisticated immune signalling pathways, pathogens make use of effector proteins to achieve the objective. This entails rapid regulation of underlying molecular mechanisms for prompt induction of associated signalling events in both plants as well as pathogens. The past decade has witnessed the emergence of post-translational modification (PTM) of proteins as a key a factor in modulating cellular responses. The ability of PTMs to expand the functional diversity of the proteome and induce rapid changes at the appropriate time enables them to play crucial roles in the regulation of plant-pathogen interactions. Therefore, this review will delve into the intricate interplay of five major PTMs involved in plant defence and pathogen countermeasures. We discuss how plants employ PTMs to fortify their immune networks, and how pathogen effectors utilize/target host modification systems to gain entry into plants and cause disease. We also emphasize the need for identification of novel PTMs and propose the use of PTM pathways as potential targets for genome editing approaches.

Imaging the spatial distribution of structurally diverse plant hormones

Plant hormones are essential and structurally diverse molecules that regulate various aspects of plant growth, development, and stress responses. However, the precise analysis of plant hormones in complex biological samples poses a challenge due to their low concentrations, dynamic levels, and intricate spatial distribution. Moreover, the complexity and interconnectedness of hormone signaling networks make it difficult to simultaneously trace multiple hormone spatial distributions. In this review, we provide an overview of currently recognized small-molecule plant hormones, signal peptide hormones, and plant growth regulators, along with the analytical methods employed for their analysis. We delve into the latest advancements in mass spectrometry imaging and in situ fluorescence techniques, which enable the examination of the spatial distribution of plant hormones. The advantages and disadvantages of these imaging techniques are further discussed. Finally, we propose potential avenues in imaging techniques to further enhance our understanding of plant hormone biology.

A GDSL motif-containing lipase modulates Sclerotinia sclerotiorum resistance in Brassica napus

Sclerotinia stem rot (SSR) caused by Sclerotinia sclerotiorum (Lib.) De Bary is a devastating disease infecting hundreds of plant species. It also restricts the yield, quality, and safe production of rapeseed (Brassica napus) worldwide. However, the lack of resistance sources and genes to S. sclerotiorum has greatly restricted rapeseed SSR-resistance breeding. In this study, a previously identified GDSL motif-containing lipase gene, B. napus GDSL LIPASE-LIKE 1 (BnaC07.GLIP1), encoding a protein localized to the intercellular space, was characterized as functioning in plant immunity to S. sclerotiorum. The BnaC07.GLIP1 promoter is S. sclerotiorum-inducible and the expression of BnaC07.GLIP1 is substantially enhanced after S. sclerotiorum infection. Arabidopsis (Arabidopsis thaliana) heterologously expressing and rapeseed lines overexpressing BnaC07.GLIP1 showed enhanced resistance to S. sclerotiorum, whereas RNAi suppression and CRISPR/Cas9 knockout B. napus lines were hyper-susceptible to S. sclerotiorum. Moreover, BnaC07.GLIP1 affected the lipid composition and induced the production of phospholipid molecules, such as phosphatidylethanolamine, phosphatidylcholine, and phosphatidic acid, which were correlated with decreased levels of reactive oxygen species (ROS) and enhanced expression of defense-related genes. A B. napus bZIP44 transcription factor specifically binds the CGTCA motif of the BnaC07.GLIP1 promoter to positively regulate its expression. BnbZIP44 responded to S. sclerotiorum infection, and its heterologous expression inhibited ROS accumulation, thereby enhancing S. sclerotiorum resistance in Arabidopsis. Thus, BnaC07.GLIP1 functions downstream of BnbZIP44 and is involved in S. sclerotiorum resistance by modulating the production of phospholipid molecules and ROS homeostasis in B. napus, providing insights into the potential roles and functional mechanisms of BnaC07.GLIP1 in plant immunity and for improving rapeseed SSR disease-resistance breeding.

Mitochondria: great balls of fire

Recent experimental studies indicate that mitochondria in mammalian cells are maintained at temperatures of at least 50 °C. While acknowledging the limitations of current experimental methods and their interpretation, we here consider the ramifications of this finding for cellular functions and for evolution. We consider whether mitochondria as heat-producing organelles had a role in the origin of eukaryotes and in the emergence of homeotherms. The homeostatic responses of mitochondrial temperature to externally applied heat imply the existence of a molecular heat-sensing system in mitochondria. While current findings indicate high temperatures for the innermost compartments of mitochondria, those of the mitochondrial surface and of the immediately surrounding cytosol remain to be determined. We ask whether some aspects of mitochondrial dynamics and motility could reflect changes in the supply and demand for mitochondrial heat, and whether mitochondrial heat production could be a factor in diseases and immunity.

Exogenous Salicylic Acid Regulates Fruiting Body Development, Secondary Metabolite Accumulation, Cell Wall Integrity, and Endogenous Salicylic Acid Content under Heat Stress in Pleurotus ostreatus

High-temperature or heat stress (HS) represents a significant environmental challenge that adversely affects crop growth and poses a substantial threat to agricultural production. Pleurotus ostreatus, recognized as the second most widely cultivated edible fungus worldwide, is particularly susceptible to the detrimental effects of HS. Enhancing the HS resistance of P. ostreatus is crucial for increasing its yield. In a prior investigation, we discovered that salicylic acid (SA) enhanced the resistance of P. ostreatus mycelia to HS through a metabolic rearrangement. The present study further investigated the effects of SA on P. ostreatus under HS. Cultivation experiments revealed that exogenous SA improved the mycelium recovery growth rate, yield, and fruiting body quality after HS. Further experiments revealed that exogenous SA mitigated the damage to the MAPK-Slt2 signal produced by HS while maintaining cell wall integrity. Furthermore, we hypothesized that the phenylalanine ammonia-lyase pathway might serve as a source for SA. In this context, we identified two salicylic hydroxylases, Po1102164 and Po1104438. Both HS and exogenous SA were found to elevate intracellular SA levels, thereby enhancing the resistance of P. ostreatus to HS.

Transcription-Aided Selection (TAS) for Crop Disease Resistance: Strategy and Evidence

A transcription-aided selection (TAS) strategy is proposed in this paper, which utilizes the positive regulatory roles of genes involved in the plant immunity pathways to screen crops with high disease resistance. Increased evidence has demonstrated that upon pathogen attack, the expression of diverse genes involved in salicylic acid (SA)-mediated SAR are differentially expressed and transcriptionally regulated. The paper discusses the molecular mechanisms of the SA signaling pathway, which plays a central role in plant immunity, and identifies differentially expressed genes (DEGs) that could be targeted for transcriptional detection. We have conducted a series of experiments to test the TAS strategy and found that the level of GmSAGT1 expression is highly correlated with soybean downy mildew (SDM) resistance with a correlation coefficient R2 = 0.7981. Using RT-PCR, we screened 2501 soybean germplasms and selected 26 collections with higher levels of both GmSAGT1 and GmPR1 (Pathogenesis-related proteins1) gene expression. Twenty-three out of the twenty-six lines were inoculated with Peronospora manshurica (Pm) in a greenhouse. Eight showed HR (highly resistant), four were R (resistant), five were MR (moderately resistant), three were S (susceptible), and three were HS (highly susceptible). The correlation coefficient R2 between the TAS result and Pm inoculation results was 0.7035, indicating a satisfactory consistency. The authors anticipate that TAS provides an effective strategy for screening crops with broad-spectrum and long-lasting resistance.

Applications of CRISPR Technologies in Forestry and Molecular Wood Biotechnology

Forests worldwide are under increasing pressure from climate change and emerging diseases, threatening their vital ecological and economic roles. Traditional breeding approaches, while valuable, are inherently slow and limited by the long generation times and existing genetic variation of trees. CRISPR technologies offer a transformative solution, enabling precise and efficient genome editing to accelerate the development of climate-resilient and productive forests. This review provides a comprehensive overview of CRISPR applications in forestry, exploring its potential for enhancing disease resistance, improving abiotic stress tolerance, modifying wood properties, and accelerating growth. We discuss the mechanisms and applications of various CRISPR systems, including base editing, prime editing, and multiplexing strategies. Additionally, we highlight recent advances in overcoming key challenges such as reagent delivery and plant regeneration, which are crucial for successful implementation of CRISPR in trees. We also delve into the potential and ethical considerations of using CRISPR gene drive for population-level genetic alterations, as well as the importance of genetic containment strategies for mitigating risks. This review emphasizes the need for continued research, technological advancements, extensive long-term field trials, public engagement, and responsible innovation to fully harness the power of CRISPR for shaping a sustainable future for forests.

Use of Bacterial Toxin-Antitoxin Systems as Biotechnological Tools in Plants

Toxin-antitoxin (TA) systems in bacteria are key regulators of the cell cycle and can activate a death response under stress conditions. Like other bacterial elements, TA modules have been widely exploited for biotechnological purposes in diverse applications, such as molecular cloning and anti-cancer therapies. However, their use in plants has been limited, leaving room for the development of new approaches. In this study, we examined two TA systems previously tested in plants, MazEF and YefM-YoeB, and identified interesting differences between them, likely related to their modes of action. We engineered modifications to these specific modules to transform them into molecular switches that can be activated by a protease, inducing necrosis in the plant cells where they are expressed. Finally, we demonstrated the antiviral potential of the modified TA modules by using, as a proof-of-concept, the potyvirus plum pox virus as an activator of the death phenotype.

The Past, Present, and Future of Plant Activators Targeting the Salicylic Acid Signaling Pathway

Plant activators have emerged as promising alternatives to conventional crop protection chemicals for managing crop diseases due to their unique mode of action. By priming the plant's innate immune system, these compounds can induce disease resistance against a broad spectrum of pathogens without directly inhibiting their proliferation. Key advantages of plant activators include prolonged defense activity, lower effective dosages, and negligible risk of pathogen resistance development. Among the various defensive pathways targeted, the salicylic acid (SA) signaling cascade has been extensively explored, leading to the successful development of commercial activators of systemic acquired resistance, such as benzothiadiazole, for widespread application in crop protection. While the action sites of many SA-targeting activators have been preliminarily mapped to different steps along the pathway, a comprehensive understanding of their precise mechanisms remains elusive. This review provides a historical perspective on plant activator development and outlines diverse screening strategies employed, from whole-plant bioassays to molecular and transgenic approaches. We elaborate on the various components, biological significance, and regulatory circuits governing the SA pathway while critically examining the structural features, bioactivities, and proposed modes of action of classical activators such as benzothiadiazole derivatives, salicylic acid analogs, and other small molecules. Insights from field trials assessing the practical applicability of such activators are also discussed. Furthermore, we highlight the current status, challenges, and future prospects in the realm of SA-targeting activator development globally, with a focus on recent endeavors in China. Collectively, this comprehensive review aims to describe existing knowledge and provide a roadmap for future research toward developing more potent plant activators that enhance crop health.

Transcriptomic and coexpression network analyses revealed the regulatory mechanism of Cydia pomonella infestation on the synthesis of phytohormones in walnut husks

The codling moth (Cydia pomonella) has a major effect on the quality and yield of walnut fruit. Plant defences respond to insect infestation by activating hormonal signalling and the flavonoid biosynthetic pathway. However, little is known about the role of walnut husk hormones and flavonoid biosynthesis in response to C. pomonella infestation. The phytohormone content assay revealed that the contents of salicylic acid (SA), abscisic acid (ABA), jasmonic acid (JA), jasmonic acid-isoleucine conjugate (JA-ILE), jasmonic acid-valine (JA-Val) and methyl jasmonate (MeJA) increased after feeding at different time points (0, 12, 24, 36, 48, and 72 h) of walnut husk. RNA-seq analysis of walnut husks following C. pomonella feeding revealed a temporal pattern in differentially expressed genes (DEGs), with the number increasing from 3,988 at 12 h to 5,929 at 72 h postfeeding compared with the control at 0 h postfeeding. Walnut husks exhibited significant upregulation of genes involved in various defence pathways, including flavonoid biosynthesis (PAL, CYP73A, 4CL, CHS, CHI, F3H, ANS, and LAR), SA (PAL), ABA (ZEP and ABA2), and JA (AOS, AOC, OPR, JAZ, and MYC2) pathways. Three gene coexpression networks that had a significant positive association with these hormonal changes were constructed based on the basis of weighted gene coexpression network analysis (WGCNA). We identified several hub transcription factors, including the turquoise module (AIL6, MYB4, PRE6, WRKY71, WRKY31, ERF003, and WRKY75), the green module (bHLH79, PCL1, APRR5, ABI5, and ILR3), and the magenta module (ERF27, bHLH35, bHLH18, TIFY5A, WRKY31, and MYB44). Taken together, these findings provide useful genetic resources for exploring the defence response mediated by phytohormones in walnut husks.

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.

Uncovering the Mechanisms: The Role of Biotrophic Fungi in Activating or Suppressing Plant Defense Responses

This paper discusses the mechanisms by which fungi manipulate plant physiology and suppress plant defense responses by producing effectors that can target various host proteins. Effector-triggered immunity and effector-triggered susceptibility are pivotal elements in the complex molecular dialogue underlying plant-pathogen interactions. Pathogen-produced effector molecules possess the ability to mimic pathogen-associated molecular patterns or hinder the binding of pattern recognition receptors. Effectors can directly target nucleotide-binding domain, leucine-rich repeat receptors, or manipulate downstream signaling components to suppress plant defense. Interactions between these effectors and receptor-like kinases in host plants are critical in this process. Biotrophic fungi adeptly exploit the signaling networks of key plant hormones, including salicylic acid, jasmonic acid, abscisic acid, and ethylene, to establish a compatible interaction with their plant hosts. Overall, the paper highlights the importance of understanding the complex interplay between plant defense mechanisms and fungal effectors to develop effective strategies for plant disease management.

A distinct protein posttranslational modifications-linked OsATL32-OsPPKL2-OsGSK2 loop modulates rice immunity against blast disease

Protein posttranslational modifications play crucial roles in plant immunity through modulating a complicated signaling network mediated by different hormones. We previously demonstrated that OsATL32, an ATL-type E3 ligase, negatively contributes to rice immunity against Magnaporthe oryzae. Here, we show that OsATL32 forms a loop with OsPPKL2 and OsGSK2 through distinct protein posttranslational modifications to modulate rice immunity. OsATL32 ubiquitinates OsPPKL2, a protein phosphatase with Kelch-like repeat domains that exerts positive roles in regulating rice immunity against M. oryzae and chitin-triggered immune responses, for degradation. The glycogen synthase kinase 2 (OsGSK2), which acts as a negative regulator of rice immunity against M. oryzae and chitin-triggered immune responses, phosphorylates OsATL32 to elevate its protein stability and E3 ligase activity on OsPPKL2. Moreover, OsPPKL2 directly dephosphorylates OsGSK2, affecting its kinase activity on substrates including OsATL32 for phosphorylation. Like OsGSK2 as a BR signaling repressor, OsATL32 negatively regulates BR signaling; conversely, OsPPKL2 plays a positive role in BR signaling. These findings provide a molecular mechanism in which OsATL32 serves as a node connecting BR signaling and immunity by associating with OsPPKL2 and OsGSK2, assembling into a distinct protein posttranslational modifications-linked loop that functions in rice BR signaling and immunity.

In-depth analysis of isochorismate synthase-derived metabolism in plant immunity: Identification of meta-substituted benzoates and salicyloyl-malate

Isochorismate-derived metabolism enables biosynthesis of the plant defense hormone salicylic acid (SA) and its derivatives. In Arabidopsis thaliana, the stress-induced accumulation of SA depends on ISOCHORISMATE SYNTHASE1 (ICS1) and also requires the presumed isochorismate transporter ENHANCED DISEASE SUSCEPTIBILITY5 (EDS5) and the GH3 enzyme avrPphB SUSCEPTIBLE3 (PBS3). By comparative metabolite and structural analyses, we identified several hitherto unreported ICS1- and EDS5-dependent, biotic stress-inducible Arabidopsis metabolites. These involve meta-substituted SA derivatives (5-formyl-SA, 5-carboxy-SA, 5-carboxymethyl-SA), their benzoic acid (BA) analogs (3-formyl-BA, 3-carboxy-BA, 3-carboxymethyl-BA), and besides the previously detected salicyloyl-aspartate (SA-Asp), the ester conjugate salicyloyl-malate (SA-Mal). SA functions as a biosynthetic precursor for SA-Mal and SA-Asp, but not for the meta-substituted SA- and BA-derivatives, which accumulate to moderate levels at later stages of bacterial infection. Interestingly, Arabidopsis leaves possess oxidizing activity to effectively convert meta-formyl- into meta-carboxy-SA/BAs. In contrast to SA, exogenously applied meta-substituted SA/BA-derivatives and SA-Mal exert a moderate impact on plant immunity and defence-related gene expression. While the isochorismate-derived metabolites are negatively regulated by the SA receptor NON-EXPRESSOR OF PR GENES1, SA conjugates (SA-Mal, SA-Asp, SA-glucose conjugates) and meta-substituted SA/BA-derivatives are oppositely affected by PBS3. Notably, our data indicate a PBS3-independent path to isochorismate-derived SA at later stages of bacterial infection, which does not considerably impact immune-related characteristics. Moreover, our results argue against a previously proposed role of EDS5 in the biosynthesis of the immune signal N-hydroxypipecolic acid and associated transport processes. We propose a significantly extended biochemical scheme of plant isochorismate metabolism that involves an alternative generation mode for benzoate- and salicylate-derivatives.

Gamma-aminobutyric acid interactions with phytohormones and its role in modulating abiotic and biotic stress in plants

Gamma-aminobutyric acid (GABA), a ubiquitous non-protein 4-carbon amino acid present in both prokaryotic and eukaryotic organisms. It is conventionally recognized as a neurotransmitter in mammals and plays a crucial role in plants. The context of this review centers on the impact of GABA in mitigating abiotic stresses induced by climate change, such as drought, salinity, heat, and heavy metal exposure. Beyond its neurotransmitter role, GABA emerges as a key player in diverse metabolic processes, safeguarding plants against multifaceted abiotic as well as biotic challenges. This comprehensive exploration delves into the GABA biosynthetic pathway, its transport mechanisms, and its intricate interplay with various abiotic stresses. The discussion extends to the nuanced relationship between GABA and phytohormones during abiotic stress acclimation, offering insights into the strategic development of mitigation strategies against these stresses. The delineation of GABA's crosstalk with phytohormones underscores its pivotal role in formulating crucial strategies for abiotic stress alleviation in plants.

Microneedle electrochemical sensor based on disposable stainless-steel wire for real-time analysis of indole-3-acetic acid and salicylic acid in tomato leaves infected by Pst DC3000 in situ

BACKGROUND

Indole-3-acetic acid (IAA) and salicylic acid (SA), pivotal regulators in plant growth, are integral to a variety of plant physiological activities. The ongoing and simultaneous monitoring of these hormones in vivo enhances our comprehension of their interactive and regulatory roles. Traditional detection methods, such as liquid chromatography-mass spectrometry, cannot obtain precise and immediate information on IAA and SA due to the complexity of sample processing. In contrast, the electrochemical detection method offers high sensitivity, rapid response times, and compactness, making it well-suited for in vivo or real-time detection applications.

RESULTS

A microneedle electrochemical sensor system crafted from disposable stainless steel (SS) wire was specifically designed for the real-time assessment of IAA and SA in plant in situ. This sensor system included a SS wire (100 μm diameter) coated with carbon cement and multi-walled carbon nanotubes, a plain platinum wire (100 μm diameter), and an Ag/AgCl wire (100 μm diameter). Differential pulse voltammetry and amperometry were adopted for detecting SA and IAA within the range of 0.1-20 μM, respectively. This sensor was applied to track IAA and SA fluctuations in tomato leaves during PstDC3000 infection, offering continuous data. Observations indicated an uptick in SA levels following infection, while IAA production was suppressed. The newly developed disposable SS wire-based microneedle electrochemical sensor system is economical, suitable for mass production, and inflicts minimal damage during the monitoring of SA and IAA in plant tissues.

SIGNIFICANCE

This disposable microneedle electrochemical sensor facilitates in vivo detection of IAA and SA in smaller plant tissues and allows for long-time monitoring of their concentrations, which not only propels research into the regulatory and interaction mechanisms of IAA and SA but also furnishes essential tools for advancing precision agriculture.

Integrated Multi-Omics Analysis to Reveal the Molecular Mechanisms of Inflorescence Elongation in Medicago sativa

The morphological architecture of inflorescence influences seed production. The regulatory mechanisms underlying alfalfa (Medicago sativa) inflorescence elongation remain unclear. Therefore, in this study, we conducted a comparative analysis of the transcriptome, proteome, and metabolome of two extreme materials at three developmental stages to explore the mechanisms underlying inflorescence elongation in alfalfa. We observed the developmental processes of long and short inflorescences and found that the elongation capacity of alfalfa with long inflorescence was stronger than that of alfalfa with short inflorescences. Furthermore, integrative analysis of the transcriptome and proteome indicated that the phenylpropanoid biosynthesis pathway was closely correlated with the structural formation of the inflorescence. Additionally, we identified key genes and proteins associated with lignin biosynthesis based on the differential expressed genes and proteins (DEGs and DEPs) involved in phenylpropanoid biosynthesis. Moreover, targeted hormone metabolome analysis revealed that IAA, GA, and CK play an important role in the peduncle elongation of alfalfa inflorescences. Based on omics analysis, we detected key genes and proteins related to plant hormone biosynthesis and signal transduction. From the WGCNA and WPCNA results, we furthermore screened 28 candidate genes and six key proteins that were correlated with lignin biosynthesis, plant hormone biosynthesis, and signaling pathways. In addition, 19 crucial transcription factors were discovered using correlation analysis that might play a role in regulating candidate genes. This study provides insight into the molecular mechanism of inflorescence elongation in alfalfa and establishes a theoretical foundation for improving alfalfa seed production.

Abolishing ARF8A activity promotes disease resistance in tomato

Auxin response factors (ARFs) are a family of transcription factors that regulate auxin-dependent developmental processes. Class A ARFs function as activators of auxin-responsive gene expression in the presence of auxin, while acting as transcriptional repressors in its absence. Despite extensive research on the functions of ARF transcription factors in plant growth and development, the extent, and mechanisms of their involvement in plant resistance, remain unknown. We have previously reported that mutations in the tomato AUXIN RESPONSE FACTOR8 (ARF8) genes SlARF8A and SlARF8B result in the decoupling of fruit development from pollination and fertilization, leading to partial or full parthenocarpy and increased yield under extreme temperatures. Here, we report that fine-tuning of SlARF8 activity results in increased resistance to fungal and bacterial pathogens. This resistance is mostly preserved under fluctuating temperatures. Thus, fine-tuning SlARF8 activity may be a potent strategy for increasing overall growth and yield.

Elicitation of salicylic acid and methyl jasmonate provides molecular and physiological evidence for potato susceptibility to infection by Erwinia carotovora subsp. carotovora

Among the range of severe plant diseases, bacterial soft rot caused by Erwinia carotovora is a significant threat to crops. This study aimed to examine the varying response patterns of distinct potato cultivars to the influence of E. carotovora. Furthermore, it seeks to highlight the potential role of salicylic acid (SA) and methyl jasmonate (MeJA) in stimulating the antioxidant defence system. We collected eight bacterial isolates from diseased and rotted tubers which were morphologically and physiologically identified as E. carotovora subsp. carotovora. We conducted a greenhouse experiment to analyse the antioxidant responses of three different potato cultivars (Diamont, Kara, and Karros) at various time intervals (2, 4, 6, 8, 12, and 24 h) after bacterial infection (hpi). We assessed the extent of disease damage by applying a foliar spray of 0.9 mM salicylic acid (SA) and 70 μM methyl jasmonate (MeJA). Inoculating with Ecc led to an increase in total phenolic levels, as well as the activities and gene expression of phenylalanine ammonia-lyase (PAL), polyphenol oxidase (PPO) and peroxidase (POX) as time progressed. Additionally, the application of SA and MeJA resulted in a further increase relative to the diseased treatments. The Karros cultivar, unlike the Diamont and Kara cultivars, demonstrated the highest expression levels of PAL, PPO and POX through inoculation, reflecting its higher levels of activity and resistance. Furthermore, the genetic response of potato cultivars to infection at 0 hpi varied depending on their susceptibility. The examination of the rate of PAL activity upregulation following SA or MeJA stimulation clarifies the cultivars' susceptibility over time. In conclusion, the study identified E. carotovora subsp. carotovora as the most virulent isolate causing soft rot disease in potato tubers. It further revealed that the Karros cultivar displayed superior resistance with high activities and gene expression of PAL, PPO and POX, while the cv. Diamont exhibited sensitivity. Additionally, foliar exposure to SA and MeJA induced antioxidant responses, enhancing the potato plants' resistance against Ecc pathogenesis and overall plant defence.

Identification of Hsp20 gene family in Malus domestica and functional characterization of Hsp20 class I gene MdHsp18.2b

Heat shock protein 20 (Hsp20) is a small molecule heat shock protein that plays an important role in plant growth, development, and stress resistance. Little is known about the function of Hsp20 family genes in apple (Malus domestica). Here, we performed a genome-wide analysis of the apple Hsp20 gene family, and a total of 49 Hsp20s genes were identified from the apple genome. Phylogenetic analysis revealed that the 49 genes were divided into 11 subfamilies, and MdHsp18.2b, a member located in the CI branch, was selected as a representative member for functional characterization. Treatment with NaCl and Botryosphaeria dothidea (B. dothidea), the causal agent of apple ring rot disease, significantly induced MdHsp18.2b transcription level. Further analysis revealed that overexpressing MdHsp18.2b reduced the resistance to salt stress but enhanced the resistance to B. dothidea infection in apple calli. Moreover, MdHsp18.2b positively regulated anthocyanin accumulation in apple calli. Physiology assays revealed that MdHsp18.2b promoted H2O2 production, even in the absence of stress factors, which might contribute to its functions in response to NaCl and B. dothidea infection. Hsps usually function as homo- or heterooligomers, and we found that MdHsp18.2b could form a heterodimer with MdHsp17.9a and MdHsp17.5, two members from the same branch with MdHsp18.2b in the phylogenetic tree. Therefore, we identified 49 Hsp20s genes from the apple genome and found that MdHsp18.2b was involved in regulating plant resistance to salt stress and B. dothidea infection, as well as in regulating anthocyanin accumulation in apple calli.