Salicylic Acid Pathway Research Articles

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

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

Identification of host gene regulation and resistance pathway dynamics at diverse infection stages of Rhizoctonia solani AG3-TB.

Rhizoctonia solani is a fungal pathogen that causes significant losses in agricultural production. Because of its rapid transmission and broad host range, the exploration of genes involved in defense responses to the infection of R. solani has become an important task. Here, we performed a time-course RNA-Seq experiment to explore crucial genes or pathways involved in host responses to R. solani AG3-TB infection at 6, 12, 24, 36, 48, and 72 hours post inoculation (hpi). GO and KEGG enrichment analysis revealed that most DEGs were enriched in the basal metabolism pathways, including carbohydrate metabolic processes and the biosynthesis of amino acids. Moreover, catalase (CAT) and superoxide dismutase (SOD) were up-regulated, and transcription factors (TFs) such as WRKY, AP2, and MYB were increased significantly compared to the control (0 hpi). Silencing of WRKY70 and catalase-3 exhibited elevated susceptibility to the fungal infection. To summarize, the TFs WRKY70 and WRKY75, genes involved in jasmonic acid (JA), salicylic acid (SA), and brassinosteroids (BR) signaling pathways, and defense-related enzymes may play crucial roles in the host responses to R. solani AG3-TB infection.

Transcriptome-wide N6-methyladenosine profiling reveals growth-defense trade-offs in the response of rice to brown planthopper (Nilaparvata lugens) infestation.

N6-Methyladenosine (m6A) is a common messenger RNA (mRNA) modification that affects various physiological processes in stress responses. However, the role of m6A modifications in plants responses to herbivore stress remains unclear. Here, we found that an infestation of brown planthopper (Nilaparvata lugens) female adults enhanced the resistance of rice to N. lugens. The m6A methylome analysis of N. lugens-infested and uninfested rice samples was performed to explore the interaction between rice and N. lugens. The m6A methylation mainly occurred in genes that were actively expressed in rice following N. lugens infestation, while an analysis of the whole-genomic mRNA distribution of m6A showed that N. lugens infestation caused an overall decrease in the number of m6A methylation sites across the chromosomes. The m6A methylation of genes involved in the m6A modification machinery and several defense-related phytohormones (jasmonic acid and salicylic acid) pathways was increased in N. lugens-infested rice compared to that in uninfested rice. In contrast, m6A modification levels of growth-related phytohormone (auxin and gibberellin) biosynthesis-related genes were significantly attenuated during N. lugens infestation, accompanied by the down-regulated expression of these transcripts, indicating that rice growth was restricted during N. lugens attack to rapidly optimize resource allocation for plant defense. Integrative analysis of the differential patterns of m6A methylation and the corresponding transcripts showed a positive correlation between m6A methylation and transcriptional regulation. The m6A modification is an important strategy for regulating the expression of genes involved in rice defense and growth during rice-N. lugens interactions. These findings provide new ideas for formulating strategies to control herbivorous pests. © 2024 Society of Chemical Industry.

Biocontrol of Fusarium head blight in rice using Bacillus velezensis JCK-7158.

Fusarium head blight (FHB) is a destructive disease caused by several species of Fusarium, such as Fusarium graminearum and F. asiaticum. FHB affects cereal crops, including wheat, barley, and rice, worldwide. Fusarium-infected kernels not only cause reduced yields but also cause quality loss by producing mycotoxins, such as trichothecenes and zearalenone, which are toxic to animals and humans. For decades, chemical fungicides have been used to control FHB because of their convenience and high control efficacy. However, the prolonged use of chemical fungicides has caused adverse effects, including the emergence of drug resistance to pathogens and environmental pollution. Biological control is considered one of the most promising alternatives to chemicals and can be used for integrated management of FHB due to the rare possibility of environment pollution and reduced health risks. In this study, Bacillus velezensis JCK-7158 isolated from rice was selected as an ecofriendly alternative to chemical fungicides for the management of FHB. JCK-7158 produced the extracellular enzymes protease, chitinase, gelatinase, and cellulase; the plant growth hormone indole-3-acetic acid; and the 2,3-butanediol precursor acetoin. Moreover, JCK-7158 exhibited broad antagonistic activity against various phytopathogenic fungi and produced iturin A, surfactin, and volatile substances as active antifungal compounds. It also enhanced the expression of PR1, a known induced resistance marker gene, in transgenic Arabidopsis plants expressing β-glucuronidase (GUS) fused with the PR1 promoter. Under greenhouse conditions, treatments with the culture broth and suspension concentrate formulation of JCK-7158 at a 1,000-fold dilution inhibited the development of FHB by 50 and 66%, respectively. In a field experiment, treatment with the suspension concentrate formulation of JCK-7158 at a 1,000-fold dilution effectively controlled the development of FHB with a control value of 55% and reduced the production of the mycotoxin nivalenol by 40%. Interestingly, treatment with JCK-7158 enhanced the expression of plant defense-related genes in salicylic acid, jasmonic acid, ethylene, and reactive oxygen species (ROS) signaling pathways before and after FHB pathogen inoculation. Taken together, our findings support that JCK-7158 has the potential to serve as a new biocontrol agent for the management of FHB.

Chloride salt enhances plant resistance to biotic stresses.

Biotic stresses caused by bacterial and fungal pathogens damage crops; identifying treatments that enhance disease resistance provides important information for understanding plant defenses and sustainable agriculture. Salt stress affects crop yields worldwide; however, studies have focused on the toxic sodium ion, leaving the effects of the chloride ion unclear. In this study, we found that irrigation with a combination of chloride salts (MgCl2, CaCl2, and KCl) suppressed the cell death phenotype of the ceramide kinase mutant acd5. Chloride salt pre-irrigation also significantly limited the cell death caused by Pseudomonas syringae pv maculicola infection and inhibited the multiplication of this bacterial pathogen in a mechanism partially dependent on the salicylic acid pathway. Moreover, chloride salt pre-irrigation improved plant defenses against the fungal pathogen challenge, confining the lesion area caused by Botrytis cinerea infection. Furthermore, the growth of herbivorous larvae of Spodoptera exigua was retarded by feeding on chloride salt irrigated plants. Thus, our data suggest that treatment with Cl- increases broad spectrum resistance to biotic challenges.

Ceramides involve sugarcane defense response to Sporisorium scitamineum

AbstractSugarcane smut, a widespread and destructive disease induced by Sporisorium scitamineum, has a significant effect on sugarcane cultivation. Sphingolipids, crucial components of membranes, play a role in plant resistance regulation. However, the specific function of sphingolipids in sugarcane smut resistance has not been understood. This study revealed that following the S. scitamineum infection, ceramide (Cer) and hydroxyceramide (hCer) levels specifically increased in the sugarcane variety ROC22, along with significant alterations in plant hormone levels. Analysis of lipid composition in S. scitamineum‐sensitive and ‐resistant sugarcane varieties indicated that the resistant variety YT93‐159 had lower Cer and hCer levels compared to the sensitive variety ROC22. Additionally, YT93‐159 displayed an increased level of jasmonoyl‐isoleucine (JA‐Ile) and upregulated the expression of genes linked to the pathway of jasmonic acid (JA). Through experiments using the sugarcane protoplast system, it was observed that exogenous ceramide could influence the expression of genes associated with the salicylic acid and JA pathways. This research was the initial examination into the lipidomics‐based molecular mechanisms underlying sugarcane's resistance to S. scitamineum, offering a theoretical foundation for enhancing sugarcane resistance through genetic engineering.

Sugarcane ScOPR1 gene enhances plant disease resistance through the modulation of hormonal signaling pathways.

Transgenic plants stably overexpressing ScOPR1 gene enhanced disease resistance by increasing the accumulation of JA, SA, and GST, as well as up-regulating the expression of genes related to signaling pathways. 12-Oxo-phytodienoate reductase (OPR) is an oxidoreductase that depends on flavin mononucleotide (FMN) and catalyzes the conversion of 12-oxophytodienoate (12-OPDA) into jasmonic acid (JA). It plays a key role in plant growth and development, and resistance to adverse stresses. In our previous study, we have obtained an OPR gene (ScOPR1, GenBank Accession Number: MG755745) from sugarcane. This gene showed positive responses to methyl jasmonate (MeJA), salicylic acid (SA), abscisic acid (ABA), and Sporisorium scitamineum, suggesting its potential for pathogen resistance. Here, in our study, we observed that Nicotiana benthamiana leaves transiently overexpressing ScOPR1 exhibited weaker disease symptoms, darker 3,3-diaminobenzidine (DAB) staining, higher accumulation of reactive oxygen species (ROS), and higher expression of hypersensitive response (HR) and SA pathway-related genes after inoculation with Ralstonia solanacearum and Fusarium solanacearum var. coeruleum. Furthermore, the transgenic N. benthamiana plants stably overexpressing the ScOPR1 gene showed enhanced resistance to pathogen infection by increasing the accumulation of JA, SA, and glutathione S-transferase (GST), as well as up-regulating genes related to HR, JA, SA, and ROS signaling pathways. Transcriptome analysis revealed that the specific differentially expressed genes (DEGs) in ScOPR1-OE were significantly enriched in hormone transduction signaling and plant-pathogen interaction pathways. Finally, a functional mechanism model of the ScOPR1 gene in response to pathogen infection was depicted. This study provides insights into the molecular mechanism of ScOPR1 and presents compelling evidence supporting its positive involvement in enhancing plant disease resistance.

Sugarcane ScCAX4 is a Negative Regulator of Resistance to Pathogen Infection.

Calcium (Ca2+) is a second messenger in various physiological processes within plants. The significance of the Ca2+/H+ exchanger (CAX) has been established in facilitating Ca2+ transport in plants; however, disease resistance functions of the CAX gene remain elusive. In this study, we conducted sequence characterization and expression analysis for a sugarcane CAX gene, ScCAX4 (GenBank Accession Number: MW206380). In order to further investigate the disease resistance functions, this gene was then transiently overexpressed in Nicotiana benthamiana leaves, which were subsequently inoculated with Fusarium solani var. coeruleum. Results showed that ScCAX4 overexpression increased the susceptibility of N. benthamiana to pathogen infection by regulating the expression of genes related to salicylic acid (SA), jasmonic acid (JA), and ethylene (ET) pathways, suggesting its negative role in disease resistance. Furthermore, we genetically transformed the ScCAX4 gene into N. benthamiana and obtained three positive T2 generation lines. Interestingly, the symptomatology of transgenic plants was consistent with that of transient overexpression after pathogen inoculation. Notably, the JA content in transgenic overexpression lines was significantly higher than that in the wild-type. RNA-seq revealed that ScCAX4 could mediate multiple signaling pathways, and the JA signaling pathway played a key role in modulating disease resistance. Finally, a regulatory model was depicted for the increased susceptibility to pathogen infection conferred by the ScCAX4 gene. This study provides genetic resources for sugarcane molecular breeding and the research direction for plant CAX genes.

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

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

Cotton SNARE complex component GhSYP121 regulates salicylic acid signaling during defense against Verticillium dahliae.

Syntaxin of plant (SYP) plays a crucial role in SNARE-mediated membrane trafficking during endocytic and secretory pathways, contributing to the regulation and execution of plant immunity against pathogens. Verticillium wilt is among the most destructive fungal diseases affecting cotton worldwide. However, information regarding SYP family genes in cotton is scarce. Through genome-wide identification and transcriptome profiling, we identified GhSYP121, a Qa SNARE gene in Gossypium hirsutum. GhSYP121 is notably induced by Verticillium dahliae, the causal agent of Verticillium wilt in cotton, and acts as a negative regulator of defense against V. dahliae. This is evidenced by the reduced resistance of GhSYP121-deficient cotton and the increased susceptibility of GhSYP121-overexpressing lines. Furthermore, the activation of the salicylic acid (SA) pathway by V. dahliae is inversely correlated with the expression level of GhSYP121. GhSYP121 interacts with its cognate SNARE component, GhSNAP33, which is required for the penetration resistance against V. dahliae in cotton. Collectively, GhSYP121, as a member of the cotton SNARE complex, is involved in regulating the SA pathway during plant defense against V. dahliae. This finding enhances our understanding of the potential role of GhSYP121 in these distinct pathways that contribute to plant defense against V. dahliae infection.

Insights into the biocontrol and plant growth promotion functions of Bacillus altitudinis strain KRS010 against Verticillium dahliae

BackgroundVerticillium wilt, caused by the fungus Verticillium dahliae, is a soil-borne vascular fungal disease, which has caused great losses to cotton yield and quality worldwide. The strain KRS010 was isolated from the seed of Verticillium wilt-resistant Gossypium hirsutum cultivar “Zhongzhimian No. 2.”ResultsThe strain KRS010 has a broad-spectrum antifungal activity to various pathogenic fungi as Verticillium dahliae, Botrytis cinerea, Fusarium spp., Colletotrichum spp., and Magnaporthe oryzae, of which the inhibition rate of V. dahliae mycelial growth was 73.97% and 84.39% respectively through confrontation test and volatile organic compounds (VOCs) treatments. The strain was identified as Bacillus altitudinis by phylogenetic analysis based on complete genome sequences, and the strain physio-biochemical characteristics were detected, including growth-promoting ability and active enzymes. Moreover, the control efficiency of KRS010 against Verticillium wilt of cotton was 93.59%. After treatment with KRS010 culture, the biomass of V. dahliae was reduced. The biomass of V. dahliae in the control group (Vd991 alone) was 30.76-folds higher than that in the treatment group (KRS010+Vd991). From a molecular biological aspect, KRS010 could trigger plant immunity by inducing systemic resistance (ISR) activated by salicylic acid (SA) and jasmonic acid (JA) signaling pathways. Its extracellular metabolites and VOCs inhibited the melanin biosynthesis of V. dahliae. In addition, KRS010 had been characterized as the ability to promote plant growth.ConclusionsThis study indicated that B. altitudinis KRS010 is a beneficial microbe with a potential for controlling Verticillium wilt of cotton, as well as promoting plant growth.

Molecular characterization revealed the role of thaumatin-like proteins of Rhizoctonia solani AG4-JY in inducing maize disease resistance.

The gene family of thaumatin-like proteins (TLPs) plays a crucial role in the adaptation of organisms to environmental stresses. In recent years, fungal secreted proteins (SP) with inducing disease resistance activity in plants have emerged as important elicitors in the control of fungal diseases. Identifying SPs with inducing disease resistance activity and studying their mechanisms are crucial for controlling sheath blight. In the present study, 10 proteins containing the thaumatin-like domain were identified in strain AG4-JY of Rhizoctonia solani and eight of the 10 proteins had signal peptides. Analysis of the TLP genes of the 10 different anastomosis groups (AGs) showed that the evolutionary relationship of the TLP gene was consistent with that between different AGs of R. solani. Furthermore, it was found that RsTLP3, RsTLP9 and RsTLP10 were regarded as secreted proteins for their signaling peptides exhibited secretory activity. Prokaryotic expression and enzyme activity analysis revealed that the three secreted proteins possess glycoside hydrolase activity, suggesting they belong to the TLP family. Additionally, spraying the crude enzyme solution of the three TLP proteins could enhance maize resistance to sheath blight. Further analysis showed that genes associated with the salicylic acid and ethylene pathways were up-regulated following RsTLP3 application. The results indicated that RsTLP3 had a good application prospect in biological control.

Physiological responses and transcriptome analysis of Hemerocallis citrina Baroni exposed to Thrips palmi feeding stress.

Thrips are serious pests of Hemerocallis citrina Baroni (daylily), affecting crop yield and quality. To defend against pests, daylily has evolved a set of sophisticated defense mechanisms. In the present study, induction of systemic resistance in Hemerocallis citrina 'Datong Huanghua' by Thrips palmi feeding was investigated at both biochemical and molecular levels. The soluble sugar content of daylily leaves was significantly lower than that in control check (CK) at all time points of feeding by T. palmi, whereas the amino acid and free fatty acid contents started to be significantly lower than those in CK after 7 days. Secondary metabolites such as tannins, flavonoids, and total phenols, which are harmful to the growth and reproduction of T. palmi, were increased significantly. The activities of defense enzymes such as peroxidase (POD), phenylalanine ammonia lyase (PAL), and polyphenol oxidase (PPO) were significantly increased, and the degree of damage to plants was reduced. The significant increase in protease inhibitor (PI) activity may lead to disrupted digestion and slower growth in T. palmi. Using RNA sequencing, 1,894 differentially expressed genes (DEGs) were identified between control and treatment groups at five timepoints. DEGs were mainly enriched in secondary metabolite synthesis, jasmonic acid (JA), salicylic acid (SA), and other defense hormone signal transduction pathways, defense enzyme synthesis, MAPK signaling, cell wall thickening, carbohydrate metabolism, photosynthesis, and other insect resistance pathways. Subsequently, 698 DEGs were predicted to be transcription factors, including bHLH and WRKY members related to biotic stress. WGCNA identified 18 hub genes in four key modules (Purple, Midnight blue, Blue, and Red) including MYB-like DNA-binding domain (TRINITY_DN2391_c0_g1, TRINITY_DN3285_c0_g1), zinc-finger of the FCS-type, C2-C2 (TRINITY_DN21050_c0_g2), and NPR1 (TRINITY_DN13045_c0_g1, TRINITY_DN855_c0_g2). The results indicate that biosynthesis of secondary metabolites, phenylalanine metabolism, PIs, and defense hormones pathways are involved in the induced resistance to T. palmi in daylily.

Elicitors of plant defenses as a standalone tactic failed to provide sufficient protection to fruits against spotted-wing drosophila

Spotted-wing drosophila, Drosophila suzukii (Matsumura), is a globally important invasive pest of soft-skinned fruits including raspberries, blueberries, and strawberries. Current control measures for this pest primarily rely on calendar-based insecticide sprays; therefore, more sustainable methods are desirable. Adults of D. suzukii use cues derived from fruits and symbiotic microbes to identify optimal sites for feeding, mating, and oviposition. We hypothesized that modifying any of these cues could influence D. suzukii adult behavior, making them less likely to select suitable fruits. One approach involves applying synthetic elicitors of the salicylic acid (SA) and jasmonic acid (JA) plant defense pathways, which are associated with defenses against pathogens and herbivores, respectively, or the use of crop sterilants, employed for microbial control, to reduce D. suzukii attraction, oviposition, and larval performance in fruits. Here, the preference and performance of D. suzukii was investigated in blueberry fruits treated exogenously with four commercial elicitors of plant defenses – three that primarily activate SA-related defenses (Actigard, LifeGard, and Regalia) and one activator of JA-related defenses (Blush) – and the crop sterilant OxiDate. A series of choice and no-choice experiments were conducted in laboratory, semi-field, and field settings that were performed at various time intervals to assess the residual effects of each treatment. Our results showed no consistent repellent, oviposition deterrent, or larval toxicity activity for any of the products tested. As a result, our findings do not provide sufficient support to recommend the use of these elicitors or the crop sterilant as viable standalone options for D. suzukii management.

Control of Peach Leaf Curl with Foliar Applications of Plant Immunity Inducers and Insights in Elicitation of Defense Responses against Taphrina deformans.

Taphrina deformans is the causal agent of leaf curl, a serious peach disease which causes significant losses in peach production worldwide. Nowadays, in order to control plant diseases, it is necessary to adopt novel and low-cost alternatives to conventional chemical fungicides. These promising strategies are targeted at eliciting host defense mechanisms via priming the host through the consecutive application of plant immunity inducers prior to pathogen challenge. In this study, we investigated whether chitosan or yeast cell wall extracts could provide enhanced tolerance against leaf curl in two-season field trials. Furthermore, we addressed the possible molecular mechanisms involved beyond the priming of immune responses by monitoring the induction of key defense-related genes. The efficacy of spraying treatments against peach leaf curl with both inducers was significantly higher compared to the untreated control, showing efficacy in reducing disease severity of up to 62.6% and 73.9% for chitosan and yeast cell wall extracts, respectively. The application of chitosan in combination with copper hydroxide was more efficient in reducing disease incidence and severity, showing efficacy values in the range of 79.5-93.18%. Peach plantlets were also spray-treated with immunity inducers three times prior to leaf inoculation with T. deformans blastospores in their yeast phase. The relative expression levels of nine key defense and priming genes, including those encoding members of pathogenesis-related (PR) proteins and hub genes associated with hormone biosynthesis, were monitored by RT-qPCR across three days after inoculation (dai). The results indicate that pre-treatments with these plant immunity inducers activated the induction of genes involved in salicylic acid (SA) and jasmonate (JA) defense signaling pathways that may offer systemic resistance, coupled with the upregulation of genes conferring direct antimicrobial effects. Our experiments suggest that these two plant immunity inducers could constitute useful components towards the effective control of T. deformans in peach crops.

Antagonistic control of rice immunity against distinct pathogens by the two transcription modules via salicylic acid and jasmonic acid pathways

Although the antagonistic effects of host resistance against biotrophic and necrotrophic pathogens have been documented in various plants, the underlying mechanisms are unknown. Here, we investigated the antagonistic resistance mediated by the transcription factor ETHYLENE-INSENSITIVE3-LIKE 3 (OsEIL3) in rice. The Oseil3 mutant confers enhanced resistance to the necrotroph Rhizoctonia solani but greater susceptibility to the hemibiotroph Magnaporthe oryzae and biotroph Xanthomonas oryzae pv. oryzae. OsEIL3 directly activates OsERF040 transcription while repressing OsWRKY28 transcription. The infection of R.solani and M.oryzae or Xoo influences the extent of binding of OsEIL3 to OsWRKY28 and OsERF040 promoters, resulting in the repression or activation of both salicylic acid (SA)- and jasmonic acid (JA)-dependent pathways and enhanced susceptibility or resistance, respectively. These results demonstrate that the distinct effects of plant immunity to different pathogen types are determined by two transcription factor modules that control transcriptional reprogramming and the SA and JA pathways.

AtVQ25 promotes salicylic acid-related leaf senescence by fine-tuning the self-repression of AtWRKY53.

Most mechanistic details of chronologically ordered regulation of leaf senescence are unknown. Regulatory networks centered on AtWRKY53 are crucial for orchestrating and integrating various senescence-related signals. Notably, AtWRKY53 binds to its own promoter and represses transcription of AtWRKY53, but the biological significance and mechanism underlying this self-repression remain unclear. In this study, we identified the VQ motif-containing protein AtVQ25 as a cooperator of AtWRKY53. The expression level of AtVQ25 peaked at mature stage and was specifically repressed after the onset of leaf senescence. AtVQ25-overexpressing plants and atvq25 mutants displayed precocious and delayed leaf senescence, respectively. Importantly, we identified AtWRKY53 as an interacting partner of AtVQ25. We determined that interaction between AtVQ25 and AtWRKY53 prevented AtWRKY53 from binding to W-box elements on the AtWRKY53 promoter and thus counteracted the self-repression of AtWRKY53. In addition, our RNA-sequencing data revealed that the AtVQ25-AtWRKY53 module is related to the salicylic acid (SA) pathway. Precocious leaf senescence and SA-induced leaf senescence in AtVQ25-overexpressing lines were inhibited by an SA pathway mutant, atsid2, and NahG transgenic plants; AtVQ25-overexpressing/atwrky53 plants were also insensitive to SA-induced leaf senescence. Collectively, we demonstrated that AtVQ25 directly attenuates the self-repression of AtWRKY53 during the onset of leaf senescence, which is substantially helpful for understanding the timing of leaf senescence onset modulated by AtWRKY53.

Screening for disease resistance and profiling the expression of defense-related genes contributing to resistance against bacterial blight (Xanthomonas oryzae pv. oryzae) in rice genotypes

Bacterial Bight profoundly affects global rice-growing regions. Breeding resistant cultivars is a reliable, effective, and eco-friendly way to control bacterial blight. The study was conducted during 2021–2022 to evaluate the resistance of rice genotypes to bacterial blight under glasshouse conditions. A total of 137 rice genotypes were screened for their resistance against two Xanthomonas oryzae pv. oryzae strains (TXO01 and TXO08) using the leaf clipping method. The results revealed diverse disease reactions among the genotypes, with some exhibiting high levels of resistance characterized by hypersensitive reactions and shorter lesion lengths. To further investigate the genetic basis of resistance, we screened moderately resistant and resistant genotypes for major bacterial blight resistance genes, including Xa21, xa5, and xa13, using gene-specific markers. Five genotypes viz., ADT55, CB MAS 13056, CB MAS 13060, CB MAS 13066, and ACM 18234 confirmed the presence of all R genes in a homozygous state, indicating a potentially robust resistance background. In addition, we examined the expression patterns of five defense-related genes involved in the salicylic acid (SA) and jasmonic acid (JA) signaling pathways using quantitative real-time PCR (qRT-PCR). The resistant genotypes exhibited significantly elevated expression levels of OsNPR1, OsWRKY45, OsPAL1, OsPR1a, and OsPR10a, ranging from 2 to 20-fold changes compared with the susceptible genotype. In conclusion, our findings suggest that the resistant genotypes not only harbor multiple bacterial blight resistance genes but also manifest up regulated defense responses against Xanthomonas oryzae pv. oryzae, possibly substantiating their elevated level of disease resistance.

Suppression of CsFAD3 in a JA-dependent manner, but not through the SA pathway, impairs drought stress tolerance in tea

The growth and yield of tea plants are seriously limited by drought stress. Fatty acid desaturases (FADs) contribute to the mediation of membrane fluidity in response to different stresses, although the role of ω-3 FAD (Omega-3 fatty acid desaturase)-mediated damage induced by drought stress in tea plants is poorly understood. In this study, drought stress significantly promoted the synthesis of C18:3 (linolenic acid) and the expression level of CsFAD3. Yeast experiments further demonstrated that CsFAD3 can convert C18:2 to C18:3, and that the 35S:GFP-CsFAD3 fusion protein was localized in the endoplasmic reticulum of Nicotiana benthamiana cells. CsFAD3-silenced tea leaves exhibited poor drought tolerance, with a lower Fv/Fm and a higher malondialdehyde (MDA) content than the control plants. However, transgenic 35S:CsFAD3 Arabidopsis plants showed the opposite phenotypes. In addition, the jasmonic acid (JA) content and the expression levels of CsLOX2, CsLOX4, CsAOS, CsAOC3 and CsOPR2 were significantly reduced in CsFAD3-silenced leaves under drought stress. However, no substantial difference in the salicylic acid (SA) content was detected under normal or drought conditions. An analysis of Atcoi1 (JA receptor) or Atnpr1 (SA receptor) mutant Arabidopsis plants in 35S:CsFAD3 backgrounds further revealed that knockout of Atcoi1 impaired the drought-tolerant phenotypes of CsFAD3 overexpression lines. Therefore, this study demonstrated that CsFAD3 plays a crucial role in drought tolerance by mediating JA pathways.

Pattern-Triggered Immunity and Effector-Triggered Immunity: crosstalk and cooperation of PRR and NLR-mediated plant defense pathways during host-pathogen interactions.

The elucidation of the molecular basis underlying plant-pathogen interactions is imperative for the development of sustainable resistance strategies against pathogens. Plants employ a dual-layered immunological detection and response system wherein cell surface-localized Pattern Recognition Receptors (PRRs) and intracellular Nucleotide-Binding Leucine-Rich Repeat Receptors (NLRs) play pivotal roles in initiating downstream signalling cascades in response to pathogen-derived chemicals. Pattern-Triggered Immunity (PTI) is associated with PRRs and is activated by the recognition of conserved molecular structures, known as Pathogen-Associated Molecular Patterns. When PTI proves ineffective due to pathogenic effectors, Effector-Triggered Immunity (ETI) frequently confers resistance. In ETI, host plants utilize NLRs to detect pathogen effectors directly or indirectly, prompting a rapid and more robust defense response. Additionally epigenetic mechanisms are participating in plant immune memory. Recently developed technologies like CRISPR/Cas9 helps in exposing novel prospects in plant pathogen interactions. In this review we explore the fascinating crosstalk and cooperation between PRRs and NLRs. We discuss epigenomic processes and CRISPR/Cas9 regulating immune response in plants andrecent findings that shed light on the coordination of these defense layers. Furthermore, we alsohave discussed the intricate interactions between the salicylic acid and jasmonic acid signalling pathways in plants, offering insights into potential synergistic interactions that would be harnessed for the development of novel and sustainable resistance strategies against diverse group of pathogens.