Immunity to pathogenic fungi in the eye.

Fusarium, Aspergillus and Candida are important fungal pathogens that cause visual impairment and blindness in the USA and worldwide. This review will summarize the epidemiology and clinical features of corneal infections and discuss the immune and inflammatory responses that play an important role in clinical disease. In addition, we describe fungal virulence factors that are required for survival in infected corneas, and the activities of neutrophils in fungal killing, tissue damage and cytokine production.

Serine hydroxymethyltransferase6 is involved in growth and resistance against pathogens via ethylene and lignin production in Arabidopsis.

Photorespiratory serine hydroxymethyltransferases (SHMTs) are important enzymes of cellular one-carbon metabolism. In this study, we investigated the potential role of SHMT6 in Arabidopsis thaliana. We found that SHMT6 is localized in the nucleus and expressed in different tissues during development. Interestingly SHMT6 is inducible in response to avirulent, virulent Pseudomonas syringae and to Fusarium oxysporum infection. Overexpression of SHMT6 leads to larger flowers, siliques, seeds, roots, and consequently an enhanced overall biomass. This enhanced growth was accompanied by increased stomatal conductance and photosynthetic capacity as well as ATP, protein, and chlorophyll levels. By contrast, a shmt6 knockout mutant displayed reduced growth. When challenged with Pseudomonas syringae pv tomato (Pst) DC3000 expressing AvrRpm1, SHMT6 overexpression lines displayed a clear hypersensitive response which was characterized by enhanced electrolyte leakage and reduced bacterial growth. In response to virulent Pst DC3000, the shmt6 mutant developed severe disease symptoms and becomes very susceptible, whereas SHMT6 overexpression lines showed enhanced resistance with increased expression of defense pathway associated genes. In response to Fusarium oxysporum, overexpression lines showed a reduction in symptoms. Moreover, SHMT6 overexpression lead to enhanced production of ethylene and lignin, which are important components of the defense response. Collectively, our data revealed that SHMT6 plays an important role in development and defense against pathogens.

FgCWM1 modulates TaNDUFA9 to inhibit SA synthesis and reduce FHB resistance in wheat.

BACKGROUND: Fusarium head blight (FHB) significantly impacts wheat yield and quality. Understanding the intricate interaction mechanisms between Fusarium graminearum (the main pathogen of FHB) and wheat is crucial for developing effective strategies to manage and this disease. Our previous studies had shown that the absence of the cell wall mannoprotein FgCWM1, located at the outermost layer of the cell wall, led to a decrease in the pathogenicity of F. graminearum and induced the accumulation of salicylic acid (SA) in wheat. Hence, we propose that FgCWM1 may play a role in interacting between F. graminearum and wheat, as its physical location facilitates interaction effects. RESULTS: In this study, we have identified that the C-terminal region of NADH dehydrogenase [ubiquinone] 1 alpha subcomplex subunit 9 (NDUFA9) could interact with FgCWM1 through the yeast two-hybrid assay. The interaction was further confirmed through the combination of Co-IP and BiFC analyses. Consistently, the results of subcellular localization indicated that TaNDUFA9 was localized in the cytoplasm adjacent to the cell membrane and chloroplasts. The protein was also detected to be associated with mitochondria and positively regulated complex I activity. The loss-of-function mutant of TaNDUFA9 exhibited a delay in flowering, decreased seed setting rate, and reduced pollen fertility. However, it exhibited elevated levels of SA and increased resistance to FHB caused by F. graminearum infection. Meanwhile, inoculation with the FgCWM1 deletion mutant strain led to increased synthesis of SA in wheat. CONCLUSIONS: These findings suggest that TaNDUFA9 inhibits SA synthesis and FHB resistance in wheat. FgCWM1 enhances this inhibition by interacting with the C-terminal region of TaNDUFA9, ultimately facilitating F. graminearum infection in wheat. This study provides new insights into the interaction mechanism between F. graminearum and wheat. TaNDUFA9 could serve as a target gene for enhancing wheat resistance to FHB.

Identification of candidate genes for Fusarium head blight resistance from QTLs using RIL population in wheat.

Fusarium head blight (FHB) stands out as one of the most devastating wheat diseases and leads to significantly grain yield losses and quality reductions in epidemic years. Exploring quantitative trait loci (QTL) for FHB resistance is a critical step for developing new FHB-resistant varieties. We previously constructed a genetic map of unigenes (UG-Map) according to the physical positions using a set of recombinant-inbred lines (RILs) derived from the cross of 'TN18 × LM6' (TL-RILs). Here, the number of diseased spikelets (NDS) and relative disease index (RDI) for FHB resistance were investigated under four environments using TL-RILs, which were distributed across 13 chromosomes. A number of 36 candidate genes for NDS and RDI from of 19 stable QTLs were identified. The average number of candidate genes per QTL was 1.89, with 14 (73.7%), two (10.5%), and three (15.8%) QTLs including one, two, and 3-10 candidate genes, respectively. Among the 24 candidate genes annotated in the reference genome RefSeq v1.1, the homologous genes of seven candidate genes, including TraesCS4B02G227300 for QNds/Rdi-4BL-4553, TraesCS5B02G303200, TraesCS5B02G303300, TraesCS5B02G303700, TraesCS5B02G303800 and TraesCS5B02G304000 for QNds/Rdi-5BL-9509, and TraesCS7A02G568400 for QNds/Rdi-7AL-14499, were previously reported to be related to FHB resistance in wheat, barely or Brachypodium distachyon. These genes should be closely associated with FHB resistance in wheat. In addition, the homologous genes of five genes, including TraesCS1A02G037600LC for QNds-1AS-2225, TraesCS1D02G017800 and TraesCS1D02G017900 for QNds-1DS-527, TraesCS1D02G018000 for QRdi-1DS-575, and TraesCS4B02G227400 for QNds/Rdi-4BL-4553, were involved in plant defense responses against pathogens. These genes should be likely associated with FHB resistance in wheat.

QTL analysis of native Fusarium head blight and deoxynivalenol resistance in 'D8006W'/'Superior', soft white winter wheat population.

BACKGROUND: Fusarium head blight (FHB), caused by Fusarium graminearum, is a major disease of wheat in North America. FHB infection causes fusarium damaged kernels (FDKs), accumulation of deoxynivalenol (DON) in the grain, and a reduction in quality and grain yield. Inheritance of FHB resistance is complex and involves multiple genes. The objective of this research was to identify QTL associated with native FHB and DON resistance in a 'D8006W'/'Superior', soft white winter wheat population. RESULTS: Phenotyping was conducted in replicated FHB field disease nurseries across multiple environments and included assessments of morphological and FHB related traits. Parental lines had moderate FHB resistance, however, the population showed transgressive segregation. A 1913.2 cM linkage map for the population was developed with SNP markers from the wheat 90 K Infinium iSelect SNP array. QTL analysis detected major FHB resistance QTL on chromosomes 2D, 4B, 5A, and 7A across multiple environments, with resistance from both parents. Trait specific unique QTL were detected on chromosomes 1A (visual traits), 5D (FDK), 6B (FDK and DON), and 7D (DON). The plant height and days to anthesis QTL on chromosome 2D coincided with Ppd-D1 and were linked with FHB traits. The plant height QTL on chromosome 4B was also linked with FHB traits; however, the Rht-B1 locus did not segregate in the population. CONCLUSIONS: This study identified several QTL, including on chromosome 2D linked with Ppd-D1, for FHB resistance in a native winter wheat germplasm.

Analyzing genetic diversity in luffa and developing a Fusarium wilt-susceptible linked SNP marker through a single plant genome-wide association (sp-GWAS) study.

BACKGROUND: Luffa (Luffa spp.) is an economically important crop of the Cucurbitaceae family, commonly known as sponge gourd or vegetable gourd. It is an annual cross-pollinated crop primarily found in the subtropical and tropical regions of Asia, Australia, Africa, and the Americas. Luffa serves not only as a vegetable but also exhibits medicinal properties, including anti-inflammatory, antidiabetic, and anticancer effects. Moreover, the fiber derived from luffa finds extensive applications in various fields such as biotechnology and construction. However, luffa Fusarium wilt poses a severe threat to its production, and existing control methods have proven ineffective in terms of cost-effectiveness and environmental considerations. Therefore, there is an urgent need to develop luffa varieties resistant to Fusarium wilt. Single-plant GWAS (sp-GWAS) has been demonstrated as a promising tool for the rapid and efficient identification of quantitative trait loci (QTLs) associated with target traits, as well as closely linked molecular markers. RESULTS: In this study, a collection of 97 individuals from 73 luffa accessions including two major luffa species underwent single-plant GWAS to investigate luffa Fusarium wilt resistance. Utilizing the double digest restriction site associated DNA (ddRAD) method, a total of 8,919 high-quality single nucleotide polymorphisms (SNPs) were identified. The analysis revealed the potential for Fusarium wilt resistance in accessions from both luffa species. There are 6 QTLs identified from 3 traits, including the area under the disease progress curve (AUDPC), a putative disease-resistant QTL, was identified on the second chromosome of luffa. Within the region of linkage disequilibrium, a candidate gene homologous to LOC111009722, which encodes peroxidase 40 and is associated with disease resistance in Cucumis melo, was identified. Furthermore, to validate the applicability of the marker associated with resistance from sp-GWAS, an additional set of 21 individual luffa plants were tested, exhibiting 93.75% accuracy in detecting susceptible of luffa species L. aegyptiaca Mill. CONCLUSION: In summary, these findings give a hint of genome position that may contribute to luffa wild resistance to Fusarium and can be utilized in the future luffa wilt resistant breeding programs aimed at developing wilt-resistant varieties by using the susceptible-linked SNP marker.

Intercropping improves faba bean photosynthesis and reduces disease caused by Fusarium commune and cinnamic acid-induced stress.

Modern intensive cropping systems often contribute to the accumulation of phenolic acids in the soil, which promotes the development of soilborne diseases. This can be suppressed by intercropping. This study analyzed the effects of intercropping on Fusarium wilt based on its effect on photosynthesis under stress by the combination of Fusarium commune and cinnamic acid. The control was not inoculated with F. commune, while the faba bean plants (Vicia faba L.) were inoculated with this pathogen in the other treatments. The infected plants were also treated with cinnamic acid. This study examined the development of Fusarium wilt together with its effects on the leaves, absorption of nutrients, chlorophyll fluorescence parameters, contents of photosynthetic pigments, activities of photosynthetic enzymes, gas exchange parameters, and the photosynthetic assimilates of faba bean from monocropping and intercropping systems. Under monocropping conditions, the leaves of the plants inoculated with F. commune grew significantly less, and there was enhanced occurrence of the Fusarium wilt compared with the control. Compared with the plants solely inoculated with F. commune, the exogenous addition of cinnamic acid to the infected plants significantly further reduced the growth of faba bean leaves and increased the occurrence of Fusarium wilt. A comparison of the combination of F. commune and cinnamic acid in intercropped wheat and faba bean compared with monocropping showed that intercropping improved the absorption of nutrients, increased photosynthetic pigments and its contents, electron transport, photosynthetic enzymes, and photosynthetic assimilates. The combination of these factors reduced the occurrence of Fusarium wilt in faba bean and increased the growth of its leaves. These results showed that intercropping improved the photosynthesis, which promoted the growth of faba bean, thus, reducing the development of Fusarium wilt following the stress of infection by F. commune and cinnamic acid. This research should provide more information to enhance sustainable agriculture.

Comprehensive genome-wide analysis of wheat xylanase inhibitor protein (XIP) genes: unveiling their role in Fusarium head blight resistance and plant immune mechanisms.

In this comprehensive genome-wide study, we identified and classified 83 Xylanase Inhibitor Protein (XIP) genes in wheat, grouped into five distinct categories, to enhance understanding of wheat's resistance to Fusarium head blight (FHB), a significant fungal threat to global wheat production. Our analysis reveals the unique distribution of XIP genes across wheat chromosomes, particularly at terminal regions, suggesting their role in the evolutionary expansion of the gene family. Several XIP genes lack signal peptides, indicating potential alternative secretion pathways that could be pivotal in plant defense against FHB. The study also uncovers the sequence homology between XIPs and chitinases, hinting at a functional diversification within the XIP gene family. Additionally, the research explores the association of XIP genes with plant immune mechanisms, particularly their linkage with plant hormone signaling pathways like abscisic acid and jasmonic acid. XIP-7A3, in particular, demonstrates a significant increase in expression upon FHB infection, highlighting its potential as a key candidate gene for enhancing wheat's resistance to this disease. This research not only enriches our understanding of the XIP gene family in wheat but also provides a foundation for future investigations into their role in developing FHB-resistant wheat cultivars. The findings offer significant implications for wheat genomics and breeding, contributing to the development of more resilient crops against fungal diseases.

Baseline tebuconazole sensitivity and potential resistant risk in Fusarium Graminearum.

BACKGROUND: The Fusarium head blight caused by Fusarium graminearum results in reduced crop yields and the potential for vomitoxin contamination, which poses a risk to both human and livestock health. The primary method of control relies on the application of chemical fungicides. RESULTS: The current study found that the tebuconazole sensitivity of 165 F. graminearum isolates collected from the Huang-Huai-Hai region of China between 2019 and 2023 ranged from 0.005 to 2.029 µg/mL, with an average EC50 value of 0.33 ± 0.03 µg/mL. The frequency distribution conformed to a unimodal curve around the mean, and therefore provides a useful reference for monitoring the emergence of tebuconazole resistance in field populations of F. graminearum. No cross-resistance was detected between tebuconazole and other unrelated fungicides such as flutriafol, propiconazole and fluazinam, but there was a clear negative cross-resistance with triazole fungicides including fludioxonil, epoxiconazole, hexaconazole, and metconazole. Analysis of five tebuconazole-resistant mutants produced under laboratory conditions indicated that although the mycelial growth of the mutants were significantly (p < 0.05) reduced, spore production and germination rates could be significantly (p < 0.05) increased. However, pathogenicity tests confirmed a severe fitness cost associated with tebuconazole resistance, as all of the mutants completely loss the ability to infect host tissue. Furthermore, in general the resistant mutants were found to have increased sensitivity to abiotic stress, such as ionic and osmotic stress, though not to Congo red and oxidative stress, to which they were more tolerant. Meanwhile, molecular analysis identified several point mutations in the CYP51 genes of the mutants, which resulted in two substitutions (I281T, and T314A) in the predicted sequence of the FgCYP51A subunit, as well as seven (S195F, Q332V, V333L, L334G, M399T, E507G, and E267G) in the FgCYP51C subunit. In addition, it was also noted that the expression of the CYP51 genes in one of the mutants, which lacked point mutations, was significantly up-regulated in response to tebuconazole treatment. CONCLUSIONS: These results provide useful data that allow for more rational use of tebuconazole in the control of F. graminearum, as well as for more effective monitoring of fungicide resistance in the field.

Characterization of the wheat-tetraploid Thinopyrum elongatum 7E(7D) substitution line with Fusarium head blight resistance.

BACKGROUND: Fusarium head blight (FHB), a devastating disease of wheat production, is predominantly elicited by Fusarium graminearum (Fg). The tetraploid Thinopyrum elongatum is a tertiary gene resource of common wheat that possesses high affinity and displays high resistance traits against multiple biotic and abiotic stress. We aim to employ and utilize the novel FHB resistance resources from the wild germplasm of common wheat for breeding. RESULTS: Durum wheat-tetraploid Th. elongatum amphiploid 8801 was hybridized with common wheat cultivars SM482 and SM51, and the F5 generation was generated. We conducted cytogenetically in situ hybridization (ISH) technologies to select and confirm a genetically stable 7E(7D) substitution line K17-1069-5, which showed FHB expansion resistance in both field and greenhouse infection experiments and displayed no significant disadvantage in agronomic traits compared to their common wheat parents in the field. The F2 segregation populations (K17-1069-5 × SM830) showed that the 7E chromosome conferred dominant FHB resistance with dosage effect. We developed 19 SSR molecular markers specific to chromosome 7E, which could be conducted for genetic mapping and large breeding populations marker-assisted selection (MAS) during selection procedures in the future. We isolated a novel Fhb7 allele from the tetraploid Th. elongatum chromosome 7E (Chr7E) using homology-based cloning, which was designated as TTE7E-Fhb7. CONCLUSIONS: In summary, our study developed a novel wheat-tetraploid Thinopyrum elongatum 7E(7D) K17-1069-5 substitution line which contains stable FHB resistance.

A delayed response in phytohormone signaling and production contributes to pine susceptibility to Fusarium circinatum.

BACKGROUND: Fusarium circinatum is the causal agent of pine pitch canker disease, which affects Pinus species worldwide, causing significant economic and ecological losses. In Spain, two Pinus species are most affected by the pathogen; Pinus radiata is highly susceptible, while Pinus pinaster has shown moderate resistance. In F. circinatum-Pinus interactions, phytohormones are known to play a crucial role in plant defense. By comparing species with different degrees of susceptibility, we aimed to elucidate the fundamental mechanisms underlying resistance to the pathogen. For this purpose, we used an integrative approach by combining gene expression and metabolomic phytohormone analyses at 5 and 10 days post inoculation. RESULTS: Gene expression and metabolite phytohormone contents suggested that the moderate resistance of P. pinaster to F. circinatum is determined by the induction of phytohormone signaling and hormone rearrangement beginning at 5 dpi, when symptoms are still not visible. Jasmonic acid was the hormone that showed the greatest increase by 5 dpi, together with the active gibberellic acid 4 and the cytokinin dehydrozeatin; there was also an increase in abscisic acid and salicylic acid by 10 dpi. In contrast, P. radiata hormonal changes were delayed until 10 dpi, when symptoms were already visible; however, this increase was not as high as that in P. pinaster. Indeed, in P. radiata, no differences in jasmonic acid or salicylic acid production were found. Gene expression analysis supported the hormonal data, since the activation of genes related to phytohormone synthesis was observed earlier in P. pinaster than in the susceptible P. radiata. CONCLUSIONS: We determine that the moderate resistance of P. pinaster to F. circinatum is in part a result of early and strong activation of plant phytohormone-based defense responses before symptoms become visible. We suggest that jasmonic acid signaling and production are strongly associated with F. circinatum resistance. In contrast, P. radiata susceptibility was attributed to a delayed response to the fungus at the moment when symptoms were visible. Our results contribute to a better understanding of the phytohormone-based defense mechanism involved in the Pinus-F. circinatum interactions and provide insight into the development of new strategies for disease mitigation.

Enhancing cowpea wilt resistance: insights from gene coexpression network analysis with exogenous melatonin treatment.

BACKGROUND: Cowpea wilt is a harmful disease caused by Fusarium oxysporum, leading to substantial losses in cowpea production. Melatonin reportedly regulates plant immunity to pathogens; however the specific regulatory mechanism underlying the protective effect of melatonin pretreated of cowpea against Fusarium oxysporum remains known. Accordingly, the study sought to evaluate changes in the physiological and biochemical indices of cowpea following melatonin treated to facilitate Fusarium oxysporum resistance and elucidate the associated molecular mechanism using a weighted gene coexpression network. RESULTS: Treatment with 100 µM melatonin was effective in increasing cowpea resistance to Fusarium oxysporum. Glutathione peroxidase (GSH-PX), catalase (CAT), and salicylic acid (SA) levels were significantly upregulated, and hydrogen peroxide (H2O2) levels were significantly downregulated in melatonin treated samples in roots. Weighted gene coexpression network analysis of melatonin- and Fusarium oxysporum-treated samples identified six expression modules comprising 2266 genes; the number of genes per module ranged from 9 to 895. In particular, 17 redox genes and 32 transcription factors within the blue module formed a complex interconnected expression network. KEGG analysis revealed that the associated pathways were enriched in secondary metabolism, peroxisomes, phenylalanine metabolism, flavonoids, and flavonol biosynthesis. More specifically, genes involved in lignin synthesis, catalase, superoxide dismutase, and peroxidase were upregulated. Additionally, exogenous melatonin induced activation of transcription factors, such as WRKY and MYB. CONCLUSIONS: The study elucidated changes in the expression of genes associated with the response of cowpea to Fusarium oxysporum under melatonin treated. Specifically, multiple defence mechanisms were initiated to improve cowpea resistance to Fusarium oxysporum.

Host RNAi-mediated silencing of Fusarium oxysporum f. sp. lycopersici specific-fasciclin-like protein genes provides improved resistance to Fusarium wilt in Solanum lycopersicum.

MAIN CONCLUSION: Tomato transgenics expressing dsRNA against FoFLPs act as biofungicides and result in enhanced disease resistance upon Fol infection, by downregulating the endogenous gene expression levels of FoFLPs within Fol. Fusarium oxysporum f. sp. lycopersici (Fol) hijacks plant immunity by colonizing within the host and further instigating secondary infection causing vascular wilt disease in tomato that leads to significant yield loss. Here, RNA interference (RNAi) technology was used to determine its potential in enduring resistance against Fusarium wilt in tomato. To gain resistance against Fol infection, host-induced gene silencing (HIGS) of Fol-specific genes encoding for fasciclin-like proteins (FoFLPs) was done by generating tomato transgenics harbouring FoFLP1, FoFLP4 and FoFLP5 RNAi constructs confirmed by southern hybridizations. These tomato transgenics were screened for stable siRNA production in T0 and T1 lines using northern hybridizations. This confirmed stable dsRNAhp expression in tomato transgenics and suggested durable trait heritability in the subsequent progenies. FoFLP-specific siRNAs producing T1 tomato progenies were further selected to ascertain its disease resistance ability using seedling infection assays. We observed a significant reduction in FoFLP1, FoFLP4 and FoFLP5 transcript levels in Fol, upon infecting their respective RNAi tomato transgenic lines. Moreover, tomato transgenic lines, expressing intended siRNA molecules in the T1 generation, exhibit delayed disease onset with improved resistance. Furthermore, reduced fungal colonization was observed in the roots of Fol-infected T1 tomato progenies, without altering the plant photosynthetic efficiency of transgenic plants. These results substantiate the cross-kingdom dsRNA or siRNA delivery from transgenic tomato to Fol, leading to enhanced resistance against Fusarium wilt disease. The results also demonstrated that HIGS is a successful approach in rendering resistance to Fol infection in tomato plants.

Investigation of the biocontrol mechanism of a novel Pseudomonas species against phytopathogenic Fusarium graminearum revealed by multi-omics integration analysis.

Phytopathogenic Fusarium graminearum poses significant threats to crop health and soil quality. Although our laboratory-cultivated Pseudomonas sp. P13 exhibited potential biocontrol capacities, its effectiveness against F. graminearum and underlying antifungal mechanisms are still unclear. In light of this, our study investigated a significant inhibitory effect of P13 on F. graminearum T1, both in vitro and in a soil environment. Conducting genomic, metabolomic, and transcriptomic analyses of P13, we sought to identify evidence supporting its antagonistic effects on T1. The results revealed the potential of P13, a novel Pseudomonas species, to produce active antifungal components, including phenazine-1-carboxylate (PCA), hydrogen cyanide (HCN), and siderophores [pyoverdine (Pvd) and histicorrugatin (Hcs)], as well as the dynamic adaptive changes in the metabolic pathways of P13 related to these active ingredients. During the logarithmic growth stage, T1-exposed P13 strategically upregulated PCA and HCN biosynthesis, along with transient inhibition of the tricarboxylic acid (TCA) cycle. However, with growth stabilization, upregulation of PCA and HCN synthesis ceased, whereas the TCA cycle was enhanced, increasing siderophores secretion (Pvd and Hcs), suggesting that this mechanism might have caused continuous inhibition of T1. These findings improved our comprehension of the biocontrol mechanisms of P13 and provided the foundation for potential application of Pseudomonas strains in the biocontrol of phytopathogenic F. graminearum. IMPORTANCE: Pseudomonas spp. produces various antifungal substances, making it an effective natural biocontrol agent against pathogenic fungi. However, the inhibitory effects and the associated antagonistic mechanisms of Pseudomonas spp. against Fusarium spp. are unclear. Multi-omics integration analyses of the in vitro antifungal effects of novel Pseudomonas species, P13, against F. graminearum T1 revealed the ability of P13 to produce antifungal components (PCA, HCN, Pvd, and Hcs), strategically upregulate PCA and HCN biosynthesis during logarithmic growth phase, and enhance the TCA cycle during stationary growth phase. These findings improved our understanding of the biocontrol mechanisms of P13 and its potential application against pathogenic fungi.

A potent endophytic fungus Purpureocillium lilacinum YZ1 protects against Fusarium infection in field-grown wheat.

Fusarium diseases pose a severe global threat to major cereal crops, particularly wheat. Existing biocontrol strains against Fusarium diseases are believed to primarily rely on antagonistic mechanisms, but not widely used under field conditions. Here, we report an endophytic fungus, Purpureocillium lilacinum YZ1, that shows promise in combating wheat Fusarium diseases. Under glasshouse conditions, YZ1 inoculation increased the survival rate of Fusarium graminearum (Fg)-infected wheat seedlings from 0% to > 60% at the seedling stage, and reduced spikelet infections by 70.8% during anthesis. In field trials, the application of YZ1 resulted in an impressive 89.0% reduction in Fg-susceptible spikelets. While a slight antagonistic effect of YZ1 against Fg was observed on plates, the induction of wheat systemic resistance by YZ1, which is distantly effective, non-specific, and long-lasting, appeared to be a key contributor to YZ1's biocontrol capabilities. Utilizing three imaging methods, we confirmed YZ1 as a potent endophyte capable of rapid colonization of wheat roots, and systematically spreading to the stem and leaves. Integrating dual RNA-Seq, photosynthesis measurements and cell wall visualization supported the link between YZ1's growth-promoting abilities and the activation of wheat systemic resistance. In conclusion, endophytes such as YZ1, which exhibits non-antagonistic mechanisms, hold significant potential for industrial-scale biocontrol applications.

The RALF2-FERONIA-MYB63 module orchestrates growth and defense in tomato roots.

Plant secreted peptides RAPID ALKALINISATION FACTORs (RALFs), which act through the receptor FERONIA (FER), play important roles in plant growth. However, it remains unclear whether and how RALF-FER contributes to the trade-off of plant growth-defense. Here, we used a variety of techniques such as CRISPR/Cas9, protein-protein interaction and transcriptional regulation methods to investigate the role of RALF2 and its receptor FER in regulating lignin deposition, root growth, and defense against Fusarium oxysporum f. sp. lycopersici (Fol) in tomato (Solanum lycopersicum). The ralf2 and fer mutants show reduced primary root length, elevated lignin accumulation, and enhanced resistance against Fol than the wild-type. FER interacts with and phosphorylates MYB63 to promote its degradation. MYB63 serves as an activator of lignin deposition by regulating the transcription of dirigent protein gene DIR19. Mutation of DIR19 suppresses lignin accumulation, and reverses the short root phenotype and Fol resistance in ralf2 or fer mutant. Collectively, our results demonstrate that the RALF2-FER-MYB63 module fine-tunes root growth and resistance against Fol through regulating the deposition of lignin in tomato roots. The study sheds new light on how plants maintain the growth-defense balance via RALF-FER.

Proline-rich protein PRPL1 enhances Panax notoginseng defence against Fusarium solani by regulating reactive oxygen species balance and strengthening the cell wall barrier.

The root rot mainly caused by Fusarium solani is a bottleneck in the cultivation of Panax notoginseng. In this study, we reported a gene encoding a plant cell wall structural protein, P. notoginseng proline-rich protein (PnPRPL1), whose transcription was upregulated by F. solani and induced by some hormone signals. The PnPRPL1 recombinant protein significantly inhibited the growth and conidial germination of the root rot pathogens. Downregulation of PnPRPL1 by RNA interference (RNAi) in P. notoginseng leaves increased the susceptibility to F. solani, whereas overexpression of PnPRPL1 in tobacco (Nicotiana tabacum) enhanced the resistance to F. solani. Compared with wild-type tobacco, the PnPRPL1-overexpressing transgenic tobacco had higher reactive oxygen species (ROS)-scavenging enzyme activities, lower ROS levels, and more lignin and callose deposition. The opposite results were obtained for the P. notoginseng expressing PnPRPL1 RNAi fragments. Furthermore, the PnPRPL1 promoter transcription activity was induced by several plant hormones and multiple stress stimuli. In addition, the transcription factor PnWRKY27 activated the expression of PnPRPL1 by directly binding to the promoter region. Thus, PnPRPL1, which is positively regulated by a WRKY transcription factor, encodes an antimicrobial protein that also mediates ROS homoeostasis and callose/lignin deposition during the response to F. solani infection.

CERK1 compromises Fusarium solani resistance by reducing jasmonate level and undergoes a negative feedback regulation via the MMK2-WRKY71 module in apple.

Fusarium spp., a necrotrophic soil-borne pathogen, causes root rot disease on many crops. CERK1, as a typical pattern recognition receptor, has been widely studied. However, the function of CERK1 during plant-Fusarium interaction has not been well described. We determined that MdCERK1 is a susceptibility gene in the apple-Fusarium solani (Fs) interaction, and jasmonic acid (JA) plays a crucial role in this process. MdCERK1 directly targets and phosphorylates the lipoxygenase MdLOX2.1, an enzyme initiating the JA biosynthesis, at positions Ser326 and Thr327. These phosphorylations inhibit its translocation from the cytosol to the chloroplasts, leading to a compromised JA biosynthesis. Fs upregulates MdCERK1 expression during infection. In turn, when the JA level is low, the apple MdWRKY71, a transcriptional repressor of MdCERK1, is markedly upregulated and phosphorylated at Thr99 and Thr102 residues by the MAP kinase MdMMK2. The phosphorylation of MdWRKY71 enhances its transcription inhibition on MdCERK1. Taken together, MdCERK1 plays a novel role in limiting JA biosynthesis. There seems to be an arms race between apple and Fs, in which Fs activates MdCERK1 expression to reduce the JA level, while apple senses the low JA level and activates the MdMMK2-MdWRKY71 module to elevate JA level by inhibiting MdCERK1 expression.

Oligogalacturonide application increases resistance to Fusarium head blight in durum wheat.

Fusariosis causes substantial yield losses in the wheat crop worldwide and compromises food safety because of the presence of toxins associated with the fungal disease. Among the current approaches to crop protection, the use of elicitors able to activate natural defense mechanisms in plants is a strategy gaining increasing attention. Several studies indicate that applications of plant cell-wall-derived elicitors, such as oligogalacturonides (OGs) derived from partial degradation of pectin, induce local and systemic resistance against plant pathogens. The aim of this study was to establish the efficacy of OGs in protecting durum wheat (Triticum turgidum subsp. durum), which is characterized by an extreme susceptibility to Fusarium graminearum. To evaluate the functionality of OGs, spikes and seedlings of cv. Svevo were inoculated with OGs, F. graminearum spores, and a co-treatment of both. Results demonstrated that OGs are active elicitors of wheat defenses, triggering typical immune marker genes and determining regulation of fungal genes. Moreover, bioassays on spikes and transcriptomic analyses on seedlings showed that OGs can regulate relevant physiological processes in Svevo with dose-dependent specificity. Thus, the OG sensing system plays an important role in fine tuning immune signaling pathways in durum wheat.

Contrasting transcriptional responses to Fusarium virguliforme colonization in symptomatic and asymptomatic hosts.

The broad host range of Fusarium virguliforme represents a unique comparative system to identify and define differentially induced responses between an asymptomatic monocot host, maize (Zea mays), and a symptomatic eudicot host, soybean (Glycine max). Using a temporal, comparative transcriptome-based approach, we observed that early gene expression profiles of root tissue from infected maize suggest that pathogen tolerance coincides with the rapid induction of senescence dampening transcriptional regulators, including ANACs (Arabidopsis thaliana NAM/ATAF/CUC protein) and Ethylene-Responsive Factors. In contrast, the expression of senescence-associated processes in soybean was coincident with the appearance of disease symptom development, suggesting pathogen-induced senescence as a key pathway driving pathogen susceptibility in soybean. Based on the analyses described herein, we posit that root senescence is a primary contributing factor underlying colonization and disease progression in symptomatic versus asymptomatic host-fungal interactions. This process also supports the lifestyle and virulence of F. virguliforme during biotrophy to necrotrophy transitions. Further support for this hypothesis lies in comprehensive co-expression and comparative transcriptome analyses, and in total, supports the emerging concept of necrotrophy-activated senescence. We propose that F. virguliforme conditions an environment within symptomatic hosts, which favors susceptibility through transcriptomic reprogramming, and as described herein, the induction of pathways associated with senescence during the necrotrophic stage of fungal development.