PR1 Expression Research Articles

Chitosan, Methyl Jasmonate, and Silicon Induce Resistance to Angular Leaf Spot in Common Bean, Caused by Pseudocercospora griseola, with Expression of Defense-Related Genes and Enzyme Activities

This study assessed the efficacy of chitosan, methyl jasmonate, and silicon in the reduction of disease severity and the induction of defense responses in common bean plants against angular leaf spot caused by Pseudocercospora griseola. The expression level of several pathogenesis-related (PR) proteins, PR1, PR2 (β-1,3-glucanase), and PR3 (chitinase), and defense-related enzymes, phenylalanine ammonia-lyase, peroxidase, and lipoxygenase, was analyzed at different time points in common bean plants after different treatments. Elicitor treatments significantly reduced disease severity 21 days after inoculation, with silicon at a 2 mM concentration proving most effective with 38.93% disease control, followed by 1 mM MeJA and 2% chitosan, respectively. Treatments with chitosan, methyl jasmonate, and silicon, regardless of pathogen infection, significantly elevated PR1, PR2, and PR3 gene expressions at 48 h after inoculation (hpi). PAL and POD activities were similarly increased following elicitor treatments and pathogen infection, especially at 48 hpi. Chemical elicitors applied post-inoculation induced PR proteins, PAL, and POD enzyme activities at 48 hpi, while LOX activity exhibited a variable fluctuation with treatments. These findings suggested that chemical elicitors, especially silicon, were effective in reducing ALS disease severity in common beans, with improved resistance associated with the expression of pathogen-responsive genes. This study is the first to analyze the expression profiles of defense-related genes in common beans treated with chemical elicitors prior to P. griseola infection.

Biocontrol Potential of Bacillus strains against soybean cyst nematode (Heterodera glycines) and for promotion of soybean growth

The soybean cyst nematode (SCN, Heterodera glycines) is the most yield-limiting pathogen in soybeans worldwide. Using chemical pesticides to control this disease is harmful to human and environment. It is urgent to develop environment-friendly nematicides. The aim of this study was to discover novel biocontrol agents on H. glycines control and soybean growth under greenhouse and field conditions Eight Bacillus strains were isolated from soil rhizosphere soils and the stability and efficiency of H. glycines was assessed in greenhouse and field experiments in 2021 and 2022. In particular, the Ba2-6 strain had the highest potential, because it was a biocontrol agent against H. glycines shown to cause 93.85% juvenile mortality. Furthermore, strains Ba 1–7, Ba2-4, and Ba2-6 effectively reduced the number of females and improved the soybean seed number per plant. Based on their morphological, physiological, biochemical and molecular (16 S rRNA) characteristics, the three strains were identified as B. aryabhattai (Ba1-7), B. megatherium (Ba2-4), and B. halotolerans (Ba2-6). The ability of Ba2-6 to induce systemic resistance to H. glycines in soybeans was investigated by the split-root system and real-time quantitative PCR experiments. The results indicated that the Ba2-6 strain induced systemic resistance to suppress the penetration of H. glycines, and enhanced gene expression of PR1, PR3a, PR5, and NPR1-2, involved in the salicylic acid and jasmonic acid pathways. The study suggests that the strains of B. aryabhattai Ba1-7, B. megatherium Ba2-4, and B. halotolerans Ba2-6 can be considered as effective biocontrol agents to control H. glycines. Further, B. halotolerans Ba2-6 not only promotes soybean growth but also enhances resistance to H. glycines by regulating defense-related gene expression and inducing systemic resistance in soybean.

Cellular changes and PR-1 gene expression accompanying infection-related morphogenesis and cell progression during invasive growth Pyricularia oryzae pathotype Triticum in resistant and susceptible wheat cultivars

Pyricularia oryzae pathotype Triticum (PoT) causes Wheat Blast, a devastating crop disease present in many wheat-producing countries. With the aim to contribute with the understanding of the mechanisms underlying pathogenesis of the fungus on wheat (Triticum aestivum), cytological and molecular studies were performed here.Susceptible and resistant interactions of wheat-PoT in cultivars of different levels of resistance were investigated by cellular changes and the molecular responses of wheat leaves according PR-1 expression. There was significant difference between susceptible (Apogee-PY15-PY34, Buck, MSINTA-PY15) and resistant (Buck-PY34, MSINTA-PY34) interactions in the responses tested. The two isolates of PoT analysed showed different ability to infect wheat plants at the cellular level during early tissue penetration analysed and documented by epi-fluorescence microscopy, patterns of PR-1 genes, and wheat plant defense reaction.Microscopic time-course analysis (24, 48, 72 and 96 h after inoculation) of individual interaction sites per leaf revealed different leaf invasion strategies of the more and less aggressive PoT isolates during the first stages of the course of pathogenesis.The results and conclusions of the present study provides the first evidence that different PR-1 spatial and temporal expression patterns occur in the early infective process of wheat-PoT, underlying two different defence mechanisms in plants according susceptible or resistant interactions. Thus, the results here laid a theoretical foundation for the future control of wheat blast using the different pattern of PR-1 gene as markers for disease resistance during the first stages of infection providing a significant contribution to a more efficient selection of wheat genotypes in breeding studies.

A comprehensive physiological and -Omic analysis of trypsin-mediated protection of green pepper fruits from chilling injury

Chilling injury (CI) in green pepper fruits during low-temperature storage causes a significant decline in quality. The present study utilized physiological, transcriptomic, and metabolomic analyses to idneitfy the mechanisms by which trypsin mitigates CI in green peppers stored at 4 °C for 8 days, followed by 3 days of shelf life. Results indicated that the trypsin treatment significantly reduced electrolyte leakage and the CI index in peppers, effectively extending their shelf life and preserving postharvest quality. After 4 days of storage, comparative -omic analyses identified 2514 differentially expressed genes (DEGs) and 397 differentially abundant metabolites (DAMs) between trypsin-treated and control peppers. The trypsin treatment induced changes in sugar metabolism, modulating the expression of HK, SUS, INV, and GLGC, which affected the abundance of metabolites such as CDP-glucose and α-D-p-glucose. Trypsin also enhanced carotenoid metabolism, altering the abundance of rhodopinal glucoside, 1′-hydroxyl-γ-carotene glucoside, and farnesyl 1-PP, and influencing the expression of PDS, CRTH, CRTB, and LUT5. Notably, the trypsin treatment activated the mitogen-activated protein kinase (MAPK) pathway that plays an integral role in the signal transduction of abiotic stress. Differential expression of FLS2, ELF18, PTO, PR1, PTI5, WPKY, MEKK1, and MPK6 genes in the MAPK pathway was observed, which was correlated with CI mitigation in green peppers during cold storage. In conclusion, trypsin is an effective treatment for reducing CI in green peppers during cold storage. The present study provides valuable insights into its physiological and molecular impact on green pepper fruit.

A novel member of miR169 family negatively regulates maize resistance against Bipolaris maydis.

MicroRNAs (miRNAs) have been confirmed to play important roles in plant defense response. However, the key maize miRNAs involved in the defense response against Bipolaris maydis are very limited. In this study, a novel member of the miR169 family in response to B. maydis, named zma-miR169s, was discovered and investigated. The expression levels of pre-miR169s and zma-miR169s were significantly repressed during B. maydis infection. CRISPR/Cas9-induced zma-miR169s mutant exhibited more resistance against B. maydis, whereas overexpression zma-miR169s enhanced susceptibility, supporting that zma-miR169s might play a negative role in maize resistance. Moreover, RNA-seq and GO analysis showed that differentially expressed genes were highly enriched in the oxidation-reduction process and plant hormone pathway. Hence, reactive oxygen species (ROS) and plant hormone levels were further investigated. ROS detection confirmed that zma-miR169s mutant accumulated more ROS, while less ROS was detected in transgenic maize OE-miR169s. Furthermore, more remarkable changes in PR-1 expression levels and salicylic acid (SA) contents were detected in zma-miR169s mutant compared to wild-type and transgenic maize during B. maydis infection. Additionally, nuclear transcription factors (NF-YA1 and NF-YA13) were identified as targets regulated by zma-miR169s through the agrobacterium-mediated transient expression method. Overexpression of ZmNF-YA13 enhanced Arabidopsis resistance to Pseudomonas syringae pv. tomato DC3000. Taken together, our results suggest that zma-miR169s negatively regulate maize defense responses by influencing ROS accumulation and the SA-dependent signaling pathway.

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.

Tomato SlWRKY3 Negatively Regulates Botrytis cinerea Resistance via TPK1b.

Botrytis cinerea is considered the second most important fungal plant pathogen, and can cause serious disease, especially on tomato. The TPK1b gene encodes a receptor-like kinase that can positively regulate plant resistance to B. cinerea. Here, we identified a tomato WRKY transcription factor SlWRKY3 that binds to the W-box on the TPK1b promoter. It can negatively regulate TPK1b transcription, then regulate downstream signaling pathways, and ultimately negatively regulate tomato resistance to B. cinerea. SlWRKY3 interference can enhance resistance to B. cinerea, and SlWRKY3 overexpression leads to susceptibility to B. cinerea. Additionally, we found that B. cinerea can significantly, and rapidly, induce the upregulation of SlWRKY3 expression. In SlWRKY3 transgenic plants, the TPK1b expression level was negatively correlated with SlWRKY3 expression. Compared with the control, the expression of the SA pathway marker gene PR1 was downregulated in W3-OE plants and upregulated in W3-Ri plants when inoculated with B. cinerea for 48 h. Moreover, SlWRKY3 positively regulated ROS production. Overall, SlWRKY3 can inhibit TPK1b transcription in tomato, and negatively regulate resistance to B. cinerea by modulating the downstream SA and ROS pathways.

Enhancing Botrytis disease management in tomato plants: insights from a Pseudomonas putida strain with biocontrol activity.

This study explores the biocontrol potential of Pseudomonas putida Z13 against Botrytis cinerea in tomato plants, addressing challenges posed by the pathogen's fungicide resistance. The aims of the study were to investigate the in vitro and in silico biocontrol traits of Z13, identify its plant-colonizing efficacy, evaluate the efficacy of different application strategies against B. cinerea in planta, and assess the capacity of Z13 to trigger induced systemic resistance (ISR) in plants. The in vitro experiments revealed that Z13 inhibits the growth of B. cinerea, produces siderophores, and exhibits swimming and swarming activity. Additionally, the Z13 genome harbors genes that encode compounds triggering ISR, such as pyoverdine and pyrroloquinoline quinone. The in planta experiments demonstrated Z13's efficacy in effectively colonizing the rhizosphere and leaves of tomato plants. Therefore, three application strategies of Z13 were evaluated against B. cinerea: root drenching, foliar spray, and the combination of root drenching and foliar spray. It was demonstrated that the most effective treatment of Z13 against B. cinerea was the combination of root drenching and foliar spray. Transcriptomic analysis showed that Z13 upregulates the expression of the plant defense-related genes PR1 and PIN2 upon B. cinerea inoculation. The results of the study demonstrated that Z13 possesses significant biocontrol traits, such as the production of siderophores, resulting in significant plant protection against B. cinerea when applied as a single treatment to the rhizosphere or in combination with leaf spraying. Additionally, it was shown that Z13 root colonization primes plant defenses against the pathogen.

Brevipalpus yothersiBaker (Tenuipalpidae) development in sweet orange plants is influenced by previous mite infestation and the presence of shelters.

Citrus leprosis is the most important viral disease affecting citrus. The disease is caused predominantly by CiLV-C and is transmitted by Brevipalpus yothersi Baker mites. This study brings some insight into the colonization of B. yothersi in citrus [(Citrus × sinensis (L.) Osbeck (Rutaceae)] previously infested by viruliferous or non-viruliferous B. yothersi. It also assesses the putative role of shelters on the behavior of B. yothersi. Expression of PR1 and PR4 genes, markers of plant defense mechanisms, were evaluated by RT-qPCR to correlate the role of the plant hormonal changes during the tri-trophic virus-mite-plant interplay. A previous infestation with either non-viruliferous and viruliferous mites positively influenced oviposition and the number of adult individuals in the resulting populations. Mite populations were higher on branches that had received a previous mite infestation than branches that did not. There was an increase in the expression of PR4, a marker gene in the jasmonic acid (JA) pathway, in the treatment with non-viruliferous mites, indicating a response from the plant to their feeding. Conversely, an induced expression of PR1, a marker gene in the salicylic acid (SA) pathway, was observed mainly in the treatment with viruliferous mites, which suggests the activation of a plant response against the pathogen. The earlier mite infestation, as well as the presence of leprosis lesions and a gypsum mixture as artificial shelters, all fostered the growth of the B. yothersi populations after the second infestation, regardless of the presence or absence of CiLV-C. Furthermore, it is suggested that B. yothersi feeding actually induces the JA pathway in plants. At the same time, the CiLV-C represses the JA pathway and induces the SA pathway, which benefits the mite vector.

Unveiling the dynamic expression of PR-1 during Musa spp. infection by Fusarium oxysporum fsp. Cubense: a cloning and characterization study.

Pathogen-related proteins (PR) are pivotal in plant defense, combating diverse biotic and abiotic stresses. While multiple gene families contribute to banana resistance against Fusarium oxysporum f sp. cubense (Foc), Pseudocercospora eumusae, and Pratylenchus coffeae, the significance of PR-1 genes in defense is paramount. Three PR-1 genes, up-regulated under diverse biotic stresses, were cloned from both resistant and susceptible cultivars of Foc, P. eumusae, and P. coffeae. Molecular characterization, phylogenetic analysis, and docking studies with the Foc TR4 CP gene were conducted. Through transcriptomic and real-time studies, three PR-1 genes (Ma02_g15050, Ma02_g15060, and Ma04_g34800) from Musa spp. were identified. These genes exhibited significant up-regulation in resistant cultivars when exposed to Foc, P. eumusae, and P. coffeae. Cloning of these genes was successfully performed from both resistant and susceptible cultivars of Foc race 1 and TR4, P. eumusae, and P. coffeae. Distinct characteristics were observed among the PR-1 genes, with groups 1 and 2 being acidic with signal peptides, and group 3 being basic without signal peptides. All cloned PR-1 proteins belonged to the CAP superfamily (PF00188). Phylogenetic analysis revealed clustering patterns for acidic PR-1 proteins, and KEGG orthology showed associations with vital pathways, including MAPK signaling, plant hormone signal transduction, and plant-pathogen interaction. Secondary and tertiary structure analyses confirmed sequence conservation across studied species. Docking studies explored interactions between the cerato-platanin (CP) gene from Foc TR4 and Ma02_g15060 from banana, suggesting the potential hindrance of PR-1 antifungal activity through direct interaction. The findings underscore the crucial role of cloned PR-1 genes in banana plant defense mechanisms against a broad spectrum of biotic stresses. These genes, especially those in groups 1 and 2, hold promise as candidates for developing stress-tolerant banana cultivars. The study provides valuable insights into the molecular aspects of banana defense strategies, emphasizing the potential applications of PR-1 genes in enhancing banana resilience.

Phase I Study of the T-Cell Receptor-like Antibody, Hu8F4 in Patients with Relapsed and Refractory Myeloid Malignancies

Background: Relapse after conventional chemotherapy for newly diagnosed AML is responsible for the majority of treatment failure. Relapsed (R/R) disease is frequently refractory to salvage attempts with further chemotherapy. The effectiveness of stem cell transplant and associated graft vs. leukemia effect implies an important role for immune-based therapy in producing long lasting remissions. Existing approaches using immunotherapy have failed to establish a suitable surface target or treatment paradigm that is effective in myeloid malignancies. Hu8F4 is a humanized T-cell receptor-like monoclonal antibody that binds to the conformational epitope of PR1 bound to HLA-A2, which is highly, differentially expressed on the surface of AML compared to normal progenitors. Methods: This is a first-in-human, Phase I dose escalation trial of Hu8F4 in patients (pts) with myeloid malignancies. Pts with R/R AML, MDS, CMML, and myeloid blast phase of CML with adequate organ function and PS ≤ 2 were eligible. Pts were treated on 7 escalating dose levels, ranging from 0.01 mg/kg to 10 mg/kg IV on D1 & 15. Initial dose levels required 1 pt per dose (0.01, 0.03, 0.1, 0.3, 1), followed by 3 pts per dose (3, 10). Results: Fifteen pts with R/R AML have been enrolled, with a median age of 62 years (range, 23-77 years), including 7 females (47%). Pts had received a median of 4 prior therapies; 5 pts (33%) had a PS of 2. At enrollment, the median WBC was 2 (0.1 - 18.4), median BM blasts were 21% (0 - 76); 9 pts (60%) had complex karyotype and 4 (27%) had a TP53 mutation. All pts had > 98% surface expression of PR1 on the myeloid blasts. Hu8F4 C max ranged up to 160,000 ng/mL with t 1/2 of 48 hours and clearance of 2.61 hr*ng/mL at the highest dose. Weak anti-drug antibodies were observed after week 4 in 2 of 3 pts treated at 3 mg/kg. With a median follow up of 5 months (1.1 - 9.9), pts have received a median of 1 (1-4) cycle of therapy. No DLTs were observed at the 3 mg/kg cohort.; 4 additional pts who were on concomitant tacrolimus were enrolled at this level to assess safety with concurrent use, and no DLTs were observed. Three pts were enrolled at the 10 mg/kg level, and 1 experienced dose limiting thrombocytopenia, triggering expansion to 6 pts. Two pts had a decline in BM blasts and 4 had stable disease. There was rapid decline in peripheral blasts immediately after infusion of Hu8F4 on D1 and 15 with associated elevation in serum LDH in some pts and a rise in normal granulocytes, consistent with drug-mediated anti-leukemia effects. The pharmacokinetic parameters and transient blast reduction indicated a possible sink effect mediated by high levels of circulating blasts. SAEs documented on study were mostly disease-related and included infections, cytopenias, hemoptysis, pneumonia, and GI bleeding. Treatment related AEs were temporally related to the drug infusion, including hypotension (Grade 2: N=2), and rigors (Grade 2: N=10; Grade 1: N=1). Infusion reactions were observed at all dose levels, more common at 3 and 10 mg/kg, but were transient, and managed with steroids and antihistamines. All pts proceeded with their next dose without further issues. Neither cytokine release syndrome nor neurologic toxicities were observed. Correlative studies support antibody dependent cellular cytotoxicity and phagocytosis as important mechanisms of anti-AML activity, which was more effective at lower dose levels. Conclusion: Hu8F4, a first-in-class TCR mimic antibody, was well tolerated with expansion planned at more frequent dose intervals. On-target peripheral blast reduction temporally related to infusion suggests biological activity. Real-time pharmacokinetic data indicate a possible sink effect that may be overcome by a more frequent dosing strategy that is planned.

Exogenous Melatonin Regulates Plant‐Disease Interaction by Inducing Maize Resistance and Decreasing the Pathogenicity of Fusarium graminearum

AbstractPlants cannot avoid environmental challenges and are constantly threatened by diverse biotic and abiotic stresses. However, plants have developed a unique immune system to defend themselves against the invasion of various pathogens. Melatonin, N‐acetyl‐5‐methoxytryptamine has positive physiological effects in plants that are involved in disease resistance. The processes underlying melatonin‐induced pathogen resistance in plants are still unknown. The current study explores how melatonin regulates the plant‐disease interaction in maize. The results showed that 400 μM melatonin strongly reduced the disease lesion on maize stalks by 1.5 cm and corn by 4.0 cm caused by Fusarium graminearum PH‐1. Furthermore, after treatment with melatonin, the plant defense enzymes like SOD significantly increased, while POD and APX significantly decreased compared to the control. In addition, melatonin can also improve maize's innate immunity, which is mediated by melatonin treatments through the salicylic acid signaling pathway, and up‐regulate the defense‐associated expression of PR1, LOX1, OXR, serPIN, and WIPI genes in maize. Melatonin not only inhibits the disease in the maize stalks and corn, but also down‐regulates the deoxynivalenol (DON) production‐related expression of genes Tri1, Tri4, Tri5, and Tri6 in maize. Overall, this study sheds new light on the mechanisms by which melatonin regulates antioxidant enzymes and defense‐related genes involved in plant immunity to effectively suppress plant diseases.

Ralstonia solanacearum effector RipAK suppresses homodimerization of the host transcription factor ERF098 to enhance susceptibility and the sensitivity of pepper plants to dehydration.

Plants have evolved a sophisticated immune system to defend against invasion by pathogens. In response, pathogens deploy copious effectors to evade the immune responses. However, the molecular mechanisms used by pathogen effectors to suppress plant immunity remain unclear. Herein, we report that an effector secreted by Ralstonia solanacearum, RipAK, modulates the transcriptional activity of the ethylene-responsive factor ERF098 to suppress immunity and dehydration tolerance, which causes bacterial wilt inpepper (Capsicum annuum L.) plants. Silencing ERF098 enhances the resistance of pepper plants to R.solanacearum infection not only by inhibiting the host colonization of R. solanacearum but also by increasing the immunity and tolerance of pepper plants to dehydration and including the closure of stomata to reduce the loss of water in an abscisic acid signal-dependent manner. In contrast, the ectopic expression of ERF098 in Nicotiana benthamiana enhances wilt disease. We also show that RipAK targets and inhibits the ERF098 homodimerization to repress the expression of salicylic acid-dependent PR1 and dehydration tolerance-related OSR1 and OSM1 by cis-elements in their promoters. Taken together, our study reveals a regulatory mechanism used by the R. solanacearum effector RipAK to increase virulence by specifically inhibiting the homodimerization of ERF098 and reprogramming the transcription of PR1, OSR1, and OSM1 to boost susceptibility and dehydration sensitivity. Thus, our study sheds light on a previously unidentified strategy by which a pathogen simultaneously suppresses plant immunity and tolerance to dehydration by secreting an effector to interfere with the activity of a transcription factor and manipulate plant transcriptional programs.

A geraniol synthase regulates plant defense via alternative splicing in tea plants.

Geraniol is an important contributor to the pleasant floral scent of tea products and one of the most abundant aroma compounds in tea plants; however, its biosynthesis and physiological function in response to stress in tea plants remain unclear. The proteins encoded by the full-length terpene synthase (CsTPS1) and its alternative splicing isoform (CsTPS1-AS) could catalyze the formation of geraniol when GPP was used as a substrate in vitro, whereas the expression of CsTPS1-AS was only significantly induced by Colletotrichum gloeosporioides and Neopestalotiopsis sp. infection. Silencing of CsTPS1 and CsTPS1-AS resulted in a significant decrease of geraniol content in tea plants. The geraniol content and disease resistance of tea plants were compared when CsTPS1 and CsTPS1-AS were silenced. Down-regulation of the expression of CsTPS1-AS reduced the accumulation of geraniol, and the silenced tea plants exhibited greater susceptibility to pathogen infection than control plants. However, there was no significant difference observed in the geraniol content and pathogen resistance between CsTPS1-silenced plants and control plants in the tea plants infected with two pathogens. Further analysis showed that silencing of CsTPS1-AS led to a decrease in the expression of the defense-related genes PR1 and PR2 and SA pathway-related genes in tea plants, which increased the susceptibility of tea plants to pathogens infections. Both in vitro and in vivo results indicated that CsTPS1 is involved in the regulation of geraniol formation and plant defense via alternative splicing in tea plants. The results of this study provide new insights into geraniol biosynthesis and highlight the role of monoterpene synthases in modulating plant disease resistance via alternative splicing.

Suppression of tomato wilt by cell-free supernatants of Acinetobacter baumannii isolates from wild cacao from the Colombian Amazon

Tomato vascular wilt caused by Fusarium oxysporum f. sp. lycopersici (Fol) is one of the most limiting diseases of this crop. The use of fungicides and varieties resistant to the pathogen has not provided adequate control of the disease. In this study, siderophore-producing bacteria isolated from wild cocoa trees from the Colombian Amazon were characterized to identify prominent strategies for plant protection. The isolates were taxonomically classified into five different genera. Eight of the fourteen were identified as bacteria of the Acinetobacter baumannii complex. Isolates CBIO024, CBIO086, CBIO117, CBIO123, and CBIO159 belonging to this complex showed the highest efficiency in siderophore synthesis, producing these molecules in a range of 91–129 µmol/L deferoxamine mesylate equivalents. A reduction in disease severity of up to 45% was obtained when plants were pretreated with CBIO117 siderophore-rich cell-free supernatant (SodSid). Regarding the mechanism of action that caused antagonistic activity against Fol, it was found that plants infected only with Fol and plants pretreated with SodSid CBIO117 and infected with Fol showed higher levels of PR1 and ERF1 gene expression than control plants. In contrast, MYC2 gene expression was not induced by the SodSid CBIO117 application. However, it was upregulated in plants infected with Fol and plants pretreated with SodSid CBIO117 and infected with the pathogen. In addition to the disease suppression exerted by SodSid CBIO117, the results suggest that the mechanism underlying this effect is related to an induction of systemic defense through the salicylic acid, ethylene, and priming defense via the jasmonic acid pathway.Graphical abstract

Defense-related gene expression in response to the application of biological control agents in banana

Black Sigatoka, caused by P. fijiensis, is the most important banana disease in Latin America as increasing applications of chemical fungicides used for its management result in both higher banana production costs and pathogen resistance. Spores of Bacillus subtilis, a proprietary Trichoderma sp., and a biological fermentation product composed of Saccharomyces cerevisiae cell walls and copper sulfate, were applied separately to evaluate potential defense responses in banana plants. The leaves were artificially inoculated with the pathogen, and the biological control agents were applied to the soil to avoid direct antagonism with the pathogen. Significantly lower (P < 0.05) area under disease progress curve values were observed among all treated plants compared with the control, with the lowest value measured in the treatment with a 5 % (w/v) concentration of a yeast cell wall product. In a second trial, the same biological control agents were applied to banana plants at 5 % (w/v) concentration to determine the relative expression of defense-related genes. Higher relative expression (P < 0.05) of PR3 and PR9 was observed at 3 and 24 h after application in the plants treated with B. subtilis and Trichoderma sp., respectively. In the plants treated with the yeast cell wall product, higher relative expression (P < 0.05) of PR3 was measured 48 h after application. The findings indicate that plant defenses may be activated by the biological control agents.

Trichoderma gamsiiT6085, a biocontrol agent of Fusarium head blight, modulates biocontrol‐relevant defence genes expression in wheat

AbstractTo enhance the framework of the mechanisms of action used by Trichoderma gamsii T6085 for the control of Fusarium head blight (FHB), this work investigated its ability to modulate the expression of defence‐related genes of wheat (Triticum aestivum ‘Apogee’) in response to endophytic colonization of plant tissues. Changes in relative expression of pal1, pr1, pgip2 and lox1 genes were assessed over time in wheat roots, in spikes colonized by T6085 alone and both T6085 and Fusarium graminearum, and in leaves from wheat seedlings root‐inoculated with T6085. Results indicate the ability of T6085 to induce local and systemic defence responses in wheat plants in the presence of one of the causal agents of FHB. There was a general significant up‐regulation of the plant defence‐related genes analysed, especially in the first days after the application of T6085. According to these results, modulation of plant defence genes could be included within the arsenal of mechanisms used by T6085 when applied to wheat, an additional feature of interest in the management of FHB. To evaluate the effect of the plant genotype on the ability of T6085 to endophytically colonize roots, root colonization was assessed on four cultivars of T. aestivum and two cultivars of T. durum. Data showed that roots of only two T. aestivum cultivars were endophytically colonized by T6085, similar to cv. Apogee used here as control, thus demonstrating an effect of the host genotype on the endophytic ability of T6085.

Cotton RSG2 Mediates Plant Resistance against Verticillium dahliae by miR482b Regulation.

Cotton Verticillium wilt, mainly caused by Verticillium dahliae, has a serious impact on the yield and quality of cotton fiber. Many microRNAs (miRNAs) have been identified to participate in plant resistance to V. dahliae infection, but the exploration of miRNA's function mechanism in plant defense is needed. Here, we demonstrate that the ghr-miR482b-GhRSG2 module mediates cotton plant resistance to V. dahliae infection. Based on the mRNA degradation data and GUS fusion experiments, ghr-miR482b directedly bonds to GhRSG2 mRNA to lead to its degradation. The knockdown and overexpression of ghr-miR482b through virus-induced gene silencing strategies enhanced (decreased by 0.39-fold in disease index compared with the control) and weakened (increased by 0.46-fold) the plant resistance to V. dahliae, respectively. In addition, silencing GhRSG2 significantly increased (increased by 0.93-fold in disease index) the plant sensitivity to V. dahliae compared with the control plants treated with empty vector. The expression levels of two SA-related disease genes, GhPR1 and GhPR2, significantly decreased in GhRSG2-silenced plants by 0.71 and 0.67 times, respectively, and in ghr-miR482b-overexpressed (OX) plants by 0.59 and 0.75 times, respectively, compared with the control, whereas the expression levels of GhPR1 and GhPR2 were significantly increased by 1.21 and 2.59 times, respectively, in ghr-miR482b knockdown (KD) plants. In sum, the ghr-miR482b-GhRSG2 module participates in the regulation of plant defense against V. dahliae by inducing the expression of PR1 and PR2 genes.

Nitric Oxide and Globin Glb1 Regulate Fusarium oxysporum Infection of Arabidopsis thaliana.

Plants continuously interact with fungi, some of which, such as Fusarium oxysporum, are lethal, leading to reduced crop yields. Recently, nitric oxide (NO) has been found to play a regulatory role in plant responses to F. oxysporum, although the underlying mechanisms involved are poorly understood. In this study, we show that Arabidopsis mutants with altered levels of phytoglobin 1 (Glb1) have a higher survival rate than wild type (WT) after infection with F. oxysporum, although all the genotypes analyzed exhibited a similar fungal burden. None of the defense responses that were analyzed in Glb1 lines, such as phenols, iron metabolism, peroxidase activity, or reactive oxygen species (ROS) production, appear to explain their higher survival rates. However, the early induction of the PR genes may be one of the reasons for the observed survival rate of Glb1 lines infected with F. oxysporum. Furthermore, while PR1 expression was induced in Glb1 lines very early on the response to F. oxysporum, this induction was not observed in WT plants.

Comparative Analysis of the Expression Profiles of Pathogenesis-Related Genes in Tomato Systemically Infected with Tobacco Mosaic and Cucumber Mosaic Viruses

In this study, we used RT-qPCR to examine how PR genes were expressed in model tomato (Solanum lycopersicum L.) plants that had been infected with TMV or CMV. Under greenhouse conditions, the indirect ELISA data showed that both viruses were detected for the first time at 6 dpi. Then, the levels of accumulation increased very quickly, reaching a peak of 15 dpi. During the course of the study (1–15 dpi), the Delta CT, NormFinder, BestKeeper, and GeNorm software tools revealed that the β-actin gene was the most informative reference gene in the virally infected tomato tissues. For both the TMV- and CMV-infected tomato plants, the transcriptional expression levels of most tested genes changed between activation and repression, especially in the first 12 dpi. Compared to mock-inoculated plants, the expression levels of PR-1 were induced at all time intervals except at 8 dpi for CMV and at 6, 7, and 8 dpi for TMV infection. Conversely, the greater activation and accumulation of both viruses were associated with the greater up-regulation of PR-2 at 8 dpi, with relative expression levels of 7.28- and 5.84-fold for TMV and CMV, respectively. The up-regulated expression of PR-3, PR-4, and PR-7 was shown at 4 dpi. In contrast, the PR-5 gene was inhibited in TMV at 1 dpi until 9 dpi, and the induction of this gene at 10 dpi increased by 1.72-fold, but PR-5 was observed to up-regulate the expression of CMV at 1 dpi. This study provides the first valuable information on the comparative transcriptional levels of these tomato genes between TMV and CMV infections.