To Tobacco Mosaic Virus Research Articles

RNA silencing is activated by N gene-mediated hypersensitive response and plays a key role in local and systemic virus resistance

AbstractIn plants, recognition between resistance gene (R) and virus induces a local hypersensitive response (HR), which is accompanied by systemic acquired resistance (SAR). The dominant resistance gene N in tobacco confers resistance to tobacco mosaic virus (TMV) at both locally inoculated tissues and systemically infected tissues. However, the mechanisms underlying HR- and SAR-mediated viral inhibition are not fully revealed. In this study, we find that Nicotiana glutinosa RNA-binding protein (NgRBP) is an RNA silencing suppressor which enhances TMV-triggered HR. Stronger HR could result in stronger local and systemic RNA silencing as well as SAR. Enhanced RNA silencing in the systemically infected leaves induced by the NgRBP gene is compromised by transient expression of NahG. These results indicate that RNA silencing is activated by HR and plays a crucial role in local and systemic virus resistance. Our results reveal a crosstalk between N gene-mediated virus resistance and RNA silencing which would deepen our understanding of the established HR and SAR models.

Proxitome profiling reveals a conserved SGT1-NSL1 signaling module that activates NLR-mediated immunity

Suppressor of G2 allele of skp1 (SGT1) is a highly conserved eukaryotic protein that plays a vital role in growth, development, and immunity in both animals and plants. Although some SGT1 interactors have been identified, the molecular regulatory network of SGT1 remains unclear. SGT1 serves as a co-chaperone to stabilize protein complexes such as the nucleotide-binding leucine-rich repeat (NLR) class of immune receptors, thereby positively regulating plant immunity. SGT1 has also been found to be associated with the SKP1-Cullin-F-box (SCF) E3 ubiquitin ligase complex. However, whether SGT1 targets immune repressors to coordinate plant immune activation remains elusive. In this study, we constructed a toolbox for TurboID- and split-TurboID-based proximity labeling (PL) assays in Nicotiana benthamiana and used the PL toolbox to explore the SGT1 interactome during pre- and post-immune activation. The comprehensive SGT1 interactome network we identified highlights a dynamic shift from proteins associated with plant development to those linked with plant immune responses. We found that SGT1 interacts with Necrotic Spotted Lesion 1 (NSL1), which negatively regulates salicylic acid-mediated defense by interfering with the nucleocytoplasmic trafficking of non-expressor of pathogenesis-related genes 1 (NPR1) during N NLR-mediated response to tobacco mosaic virus. SGT1 promotes the SCF-dependent degradation of NSL1 to facilitate immune activation, while salicylate-induced protein kinase-mediated phosphorylation of SGT1 further potentiates this process. Besides N NLR, NSL1 also functions in several other NLR-mediated immunity. Collectively, our study unveils the regulatory landscape of SGT1 and reveals a novel SGT1-NSL1 signaling module that orchestrates plant innate immunity.

Integrated transcriptome and metabolome reveal that SlSYTA modulates ROS responses driving resistance defense in Solanum lycopersicum.

Synaptotagmin A (SYTA), renowned for its indispensable role in mammalian vesicle trafficking, has recently captured attention in plant biology owing to its potential regulatory functions. This study meticulously delves into the involvement of Solanum lycopersicum SlSYTA in plant immunity, focusing on its response to an array of pathogens affecting tomatoes. Our comprehensive inquiry uncovers that SlSYTA overexpression heightens susceptibility to tobacco mosaic virus (TMV), Phytophthora capsici, Botrytis cinerea, and Pseudomonas syringae pv. tomato DC3000, whereas RNA interference (RNAi) plants show a robust and encompassing resistance to these pathogens. Remarkably, our findings shed light on SlSYTA's negative regulation of pivotal aspects of pattern-triggered immunity (PTI) defense, notably hindering the reactive oxygen species (ROS) burst, impeding stomatal closure, and curtailing callose deposition. Through meticulous scrutiny via transcriptome and metabolome analyses, our studies reveal SlSYTA's profound impact on diverse plant defense pathways, specifically influencing phenylpropanoid metabolism, hormone signaling, and oxidative phosphorylation, primarily via NADPH synthesis modulation in the pentose phosphate pathway, and ultimately interplay within ROS signaling. Collectively, our research presents groundbreaking insights into the intricate molecular mechanisms governing plant immunity, emphasizing the significant role of SlSYTA in orchestrating plant responses to biotic stress.

Morphological characterization and molecular marker-assisted selection for resistance to Tobacco mosaic virus (TMV) and Tomato spotted wilt virus (TSWV) in S2 population of capia pepper (Capsicum annuum L.)

Morphological characterization and molecular marker-assisted selection for resistance to Tobacco mosaic virus (TMV) and Tomato spotted wilt virus (TSWV) in S2 population of capia pepper (Capsicum annuum L.)

CDC48 regulates immunity pathway in tobacco plants

The CDC48 protein, highly conserved in the living kingdom, is a player of the ubiquitin proteasome system and contributes to various cellular processes. In plants, CDC48 is involved in cell division, plant growth and, as recently highlighted in several reports, in plant immunity. In the present study, to further extend our knowledge about CDC48 functions in plants, we analysed the incidence of its overexpression on tobacco development and immune responses. CDC48 overexpression disrupted plant development and morphology, induced changes in plastoglobule appearance and exacerbated ROS production. In addition, levels of salicylic acid (SA) and glycosylated SA were higher in transgenic plants, both in the basal state and in response to cryptogein, a protein produced by the oomycete Phytophthora cryptogea triggering defence responses. The expression of defence genes, notably those coding for some pathogenesis-related (PR) proteins, was also exacerbated in the basal state in transgenic plant lines. Finally, tobacco plants overexpressing CDC48 did not develop necrosis in response to tobacco mosaic virus (TMV) infection, suggesting a role for CDC48 in virus resistance.

Conserved transcription factors NRZ1 and NRM1 regulate NLR receptor-mediated immunity.

Plant innate immunity mediated by the nucleotide-binding leucine-rich repeat (NLR) class of immune receptors plays an important role in defense against various pathogens. Although key biochemical events involving NLR activation and signaling have been recently uncovered, we know very little about the transcriptional regulation of NLRs and their downstream signaling components. Here, we show that the Toll-Interleukin 1 receptor homology domain containing NLR (TNL) gene N (Necrosis), which confers resistance to Tobacco mosaic virus, is transcriptionally induced upon immune activation. We identified two conserved transcription factors, N required C3H zinc finger 1 (NRZ1) and N required MYB-like transcription factor 1 (NRM1), that activate N in an immune responsive manner. Genetic analyses indicated that NRZ1 and NRM1 positively regulate coiled-coil domain-containing NLR- and TNL-mediated immunity and function independently of the signaling component Enhanced Disease Susceptibility 1. Furthermore, NRZ1 functions upstream of NRM1 in cell death signaling, and their gene overexpression induces ectopic cell death and expression of NLR signaling components. Our findings uncovered a conserved transcriptional regulatory network that is central to NLR-mediated cell death and immune signaling in plants.

Nicotiana benthamiana Class 1 Reversibly Glycosylated Polypeptides Suppress Tobacco Mosaic Virus Infection.

Reversibly glycosylated polypeptides (RGPs) have been identified in many plant species and play an important role in cell wall formation, intercellular transport regulation, and plant-virus interactions. Most plants have several RGP genes with different expression patterns depending on the organ and developmental stage. Here, we report on four members of the RGP family in N. benthamiana. Based on a homology search, NbRGP1-3 and NbRGP5 were assigned to the class 1 and class 2 RGPs, respectively. We demonstrated that NbRGP1-3 and 5 mRNA accumulation increases significantly in response to tobacco mosaic virus (TMV) infection. Moreover, all identified class 1 NbRGPs (as distinct from NbRGP5) suppress TMV intercellular transport and replication in N. benthamiana. Elevated expression of NbRGP1-2 led to the stimulation of callose deposition at plasmodesmata, indicating that RGP-mediated TMV local spread could be affected via a callose-dependent mechanism. It was also demonstrated that NbRGP1 interacts with TMV movement protein (MP) in vitro and in vivo. Therefore, class 1 NbRGP1-2 play an antiviral role by impeding intercellular transport of the virus by affecting plasmodesmata callose and directly interacting with TMV MP, resulting in the reduced viral spread and replication.

Discovery of Chiral Diamine Derivatives Containing 1,2-Diphenylethylenediamine as Novel Antiviral and Fungicidal Agents.

Severe plant virus diseases lead to poor harvests and poor crop quality, and the lack of effective suppressive drugs makes plant disease control a huge challenge. Natural product-based structural simplification is an important strategy for finding novel pesticide candidates. According to our previous research on the antiviral activities of harmine and tetrahydroharmine derivatives, a series of chiral diamine compounds were designed and synthesized by means of structural simplification using diamines in natural products as the core structure in this work, and the antiviral and fungicidal activities were investigated. Most of these compounds displayed higher antiviral activities than those of ribavirin. Compounds 1a and 4g displayed higher antiviral activities than ningnanmycin at 500 μg/mL. The antiviral mechanism research revealed that compounds 1a and 4g could inhibit virus assembly by binding to tobacco mosaic virus (TMV) CP and interfere with the assembly process of TMV CP and RNA via transmission electron microscopy and molecular docking. Further fungicidal activity tests showed that these compounds displayed broad-spectrum fungicidal activities. Compounds 3a, 3i, 5c, and 5d with excellent fungicidal activities against Fusarium oxysporum f.sp. cucumerinum can be considered as new fungicidal candidates for further research. The current work provides a reference to the development of agricultural active ingredients in crop protection.

Rootstock-induced scion resistance against tobacco mosaic virus is associated with the induction of defence-related transcripts and graft-transmissible mRNAs.

Grafting is a common horticultural practice used to confer desirable traits between rootstock and scion, including disease resistance. To investigate graft-conferred resistance against viral diseases a novel heterografting system was developed using Nicotiana benthamiana scions grafted onto different tomato rootstocks. N. benthamiana is normally highly susceptible to tobacco mosaic virus (TMV) infection. However, specific tomato rootstock varieties were found to confer a range of resistance levels to N. benthamiana scions inoculated with TMV. Conferred resistance was associated with delays in virus accumulation and the reduction in virus spread. RNA sequencing analysis showed the enrichment of transcripts associated with disease resistance and plant stress in N. benthamiana scions grafted onto resistance-inducing tomato rootstocks. Genome sequencing of resistance- and nonresistance-conferring rootstocks was used to identify mobile tomato transcripts within N. benthamiana scions. Within resistance-induced N. benthamiana scions, enriched mobile tomato transcripts were predominantly associated with defence, stress, and abscisic acid signalling when compared to similar scions grafted onto nonresistance-inducing rootstock. Combining these findings suggests that graft-induced resistance is modulated by rootstock scion transcriptional responses and rootstock-specific mobile transcripts.

A Conserved, Serine-Rich Protein Plays Opposite Roles in N-Mediated Immunity against TMV and N-Triggered Cell Death.

Plant nucleotide-binding, leucine-rich, repeat-containing proteins (NLRs) play important roles in plant immunity. NLR expression and function are tightly regulated by multiple mechanisms. In this study, a conserved serine/arginine-rich protein (SR protein) was identified through the yeast one-hybrid screening of a tobacco cDNA library using DNA fragments from the N gene, an NLR that confers immunity to tobacco mosaic virus (TMV). This SR protein showed an interaction with a 3' genomic regulatory sequence (GRS) and has a potential role in regulating the alternative splicing of N. Thus, it was named SR regulator for N, abbreviated SR4N. Further study showed that SR4N plays a positive role in N-mediated cell death but a negative role in N protein accumulation. SR4N also promotes multiple virus replications in co-expression experiments, and this enhancement may not function through RNA silencing suppression, as it did not enhance 35S-GFP expression in co-infiltration experiments. Bioinformatic and molecular studies revealed that SR4N belongs to the SR2Z subtype of the SR protein family, which was conserved in both dicots and monocots, and its roles in repressing viral immunity and triggering cell death were also conserved. Our study revealed new roles for SR2Z family proteins in plant immunity against viruses.

Antivirus isoindolinone alkaloids with rare oxocyclopenta[f]isoindole frameworks isolated from the stems of flue cured tobacco

BackgroundSince Nicotiana tabacum (tobacco) has important significance to humans for their medicinal uses, to find antivirus activities inhibitors from tobacco, increase its medicinal value, and comprehensive utilization of its by-products, our group had investigated the chemical constituents of the stems of Y-202, a cultivar of tobacco which high resistance to tobacco mosaic virus (TMV).ResultsFour new isoindolinone-type alkaloids, nicoisoindoles A–D (1–4), along with four known isoindole derivatives (5–8) were isolated. Compounds 1–4 represent a new subclass of isoindolinone alkaloids with rare cyclopenta[f]isoindole-1-one frameworks. Among them, nicoisoindole C (3) possesses an unusual N-2-(5-methoxy-6-methylpyridin-2-yl) ethyl moiety, while nicoisoindole D (4) has a novel a N-(3-methyl-6-oxo-1,6-dihydropyridin-2-yl)methyl substituent. Interestingly, compounds 1, 3, and 4 showed high anti-TMV activities with inhibition rates of 43.8%, 58.8%, and 67.8% at the concentration of 20 μM, and IC50 values of 23.6, 19.5 and 15.4 μM, respectively, even more potent than that of positive control.ConclusionsThe successful isolation and structure identification of new oxocyclopenta[f]isoindole-1-ones provide materials for the screening of antivirus activities inhibitors, and contribute to the development and utilization of the waste from tobacco cultivation.Graphical

Bioconjugation Strategies for Tobacco Mild Green Mosaic Virus.

Tobacco mild green mosaic virus (TMGMV) is a plant virus closely related to Tobacco mosaic virus (TMV), sharing many of its structural and chemical features. These rod-shaped viruses, comprised of 2130 identical coat protein subunits, have been utilized as nanotechnological platforms for a myriad of applications, ranging from drug delivery to precision agriculture. This versatility for functionalization is due to their chemically active external and internal surfaces. While both viruses are similar, they do exhibit some key differences in their surface chemistry, suggesting the reactive residue distribution on TMGMV should not overlap with TMV. In this work, we focused on the establishment and refinement of chemical bioconjugation strategies to load molecules into or onto TMGMV for targeted delivery. A combination of NHS, EDC, and diazo coupling reactions in combination with click chemistry were used to modify the N-terminus, glutamic/aspartic acid residues, and tyrosines in TMGMV. We report loading with over 600 moieties per TMGMV via diazo-coupling, which is a >3-fold increase compared to previous studies. We also report that cargo can be loaded to the solvent-exposed N-terminus and carboxylates on the exterior/interior surfaces. Mass spectrometry revealed the most reactive sites to be Y12 and Y72, both tyrosine side chains are located on the exterior surface. For the carboxylates, interior E106 (66.53 %) was the most reactive for EDC-propargylamine coupled reactions, with the exterior E145 accounting for >15 % reactivity, overturning previous assumptions that only interior glutamic acid residues are accessible. A deeper understanding of the chemical properties of TMGMV further enables its functionalization and use as a multifunctional nanocarrier platform for applications in medicine and precision farming.

FvZFP1 confers transgenic Nicotiana benthamiana resistance against plant pathogens and improves tolerance to abiotic stresses

Zinc finger proteins can induce plant resistance and activate the expression of molecules involved in the resistance pathway in response to harsh environmental conditions. Previously, we found that a novel Fragaria vesca zinc finger protein interacts with the P6 protein encoded by a strawberry vein banding virus. However, the molecular mechanism of the zinc finger protein in plant stress resistance is still unknown. In this study, we reported the identification and functional characterization of the RING finger and CHY zinc finger domain-containing protein 1 (FvZFP1). The overexpression of FvZFP1 in Nicotiana benthamiana enhanced resistance to tobacco mosaic virus (TMV) and Pseudomonas syringae pv. tomato DC3000 (Pst DC3000) infection by increasing ROS content. Additionally, FvZFP1 overexpression upregulated salicylic acid (SA) response-related gene expression as well as SA accumulation following TMV and Pst DC3000 infection. Furthermore, FvZFP1 overexpression resulted in increased salinity and drought stress tolerance by increasing SOD activity and decreasing MDA content. Overexpression of FvZFP1 also activated the ABA pathway under salinity or drought conditions. To our knowledge, this is the first study on the involvement of F. vesca zinc finger protein in crosstalk between biotic and abiotic stress signaling pathways, suggesting that FvZFP1 is a candidate gene for the improvement of resistance in response to multiple stresses.

Two TOBAMOVIRUS MULTIPLICATION 2A homologs in tobacco control asymptomatic response to tobacco mosaic virus.

The most common response of a host to pathogens is arguably the asymptomatic response. However, the genetic and molecular mechanisms responsible for asymptomatic responses to pathogens are poorly understood. Here we report on the genetic cloning of two genes controlling the asymptomatic response to tobacco mosaic virus (TMV) in cultivated tobacco (Nicotiana tabacum). These two genes are homologous to tobamovirus multiplication 2A (TOM2A) from Arabidopsis, which was shown to be critical for the accumulation of TMV. Expression analysis indicates that the TOM2A genes might play fundamental roles in plant development or in responses to stresses. Consistent with this hypothesis, a null allele of the TOM2A ortholog in tomato (Solanum lycopersicum) led to the development of bent branches and a high tolerance to both TMV and tomato mosaic virus (ToMV). However, the TOM2A ortholog in Nicotiana glauca did not account for the asymptomatic response to TMV in N. glauca. We showed that TOM2A family is plant-specific and originated from Chlorophyte, and the biological functions of TOM2A orthologs to promote TMV accumulation are highly conserved in the plant kingdom-in both TMV host and nonhost species. In addition, we showed that the interaction between tobacco TOM1 and TOM2A orthologs in plant species is conserved, suggesting a conserved nature of TOM1-TOM2A module in promoting TMV multiplication in plants. The tradeoff between host development, the resistance of hosts to pathogens, and their influence on gene evolution are discussed. Our results shed light on mechanisms that contribute to asymptomatic responses to viruses in plants and provide approaches for developing TMV/ToMV-resistant crops.

Dual Roles of GSNOR1 in Cell Death and Immunity in Tetraploid Nicotiana tabacum.

S-nitrosoglutathione reductase 1 (GSNOR1) is the key enzyme that regulates cellular homeostasis of S-nitrosylation. Although extensively studied in Arabidopsis, the roles of GSNOR1 in tetraploid Nicotiana species have not been investigated previously. To study the function of NtGSNOR1, we knocked out two NtGSNOR1 genes simultaneously in Nicotiana tabacum using clustered regularly interspaced short palindromic repeats (CRISPR)/caspase 9 (Cas9) technology. To our surprise, spontaneous cell death occurred on the leaves of the CRISPR/Cas9 lines but not on those of the wild-type (WT) plants, suggesting that NtGSNOR1 negatively regulates cell death. The natural cell death on the CRISPR/Cas9 lines could be a result from interactions between overaccumulated nitric oxide (NO) and hydrogen peroxide (H2O2). This spontaneous cell death phenotype was not affected by knocking out two Enhanced disease susceptibility 1 genes (NtEDS11a/1b) and thus was independent of the salicylic acid (SA) pathway. Unexpectedly, we found that the NtGSNOR1a/1b knockout plants displayed a significantly (p < 0.001) enhanced resistance to paraquat-induced cell death compared to WT plants, suggesting that NtGSNOR1 functions as a positive regulator of the paraquat-induced cell death. The increased resistance to the paraquat-induced cell death of the NtGSNOR1a/1b knockout plants was correlated with the reduced level of H2O2 accumulation. Interestingly, whereas the N gene-mediated resistance to Tobacco mosaic virus (TMV) was significantly enhanced (p < 0.001), the resistance to Pseudomonas syringae pv. tomato DC3000 was significantly reduced (p < 0.01) in the NtGSNOR1a/1b knockout lines. In summary, our results indicate that NtGSNOR1 functions as both positive and negative regulator of cell death under different conditions and displays distinct effects on resistance against viral and bacterial pathogens.

Rhodopseudomonas palustris Quorum Sensing Molecule pC-HSL Induces Systemic Resistance to TMV Infection via Upregulation of NbSIPK/NbWIPK Expressions in Nicotiana benthamiana.

G-negative bacteria produce myriad N-acyl-homoserine lactones (AHLs) that can function as quorum sensing (QS) signaling molecules. AHLs are also known to regulate various plant biological activities. p-Coumaroyl-homoserine lactone (pC-HSL) is the only QS molecule produced by a photosynthetic bacterium, Rhodopseudomonas palustris. The role of pC-HSL in the interaction between R. palustris and plant has not been investigated. In this study, we investigated the effect of pC-HSL on plant immunity and found that this QS molecule can induce a systemic resistance to Tobacco mosaic virus (TMV) infection in Nicotiana benthamiana. The results show that pC-HSL treatment can prolong the activation of two mitogen-associated protein kinase genes (i.e., NbSIPK and NbWIPK) and increase the expression of transcription factor WRKY8 as well as immune response marker genes NbPR1 and NbPR10, leading to an increased accumulation of reactive oxygen species (ROS) in the TMV-infected plants. Our results also show that pC-HSL treatment can increase activities of two ROS-scavenging enzymes, peroxidase and superoxide dismutase. Knockdown of NbSIPK or NbWIPK expression in N. benthamiana plants through virus-induced gene silencing nullified or attenuated pC-HSL-induced systemic resistance, indicating that the functioning of pC-HSL relies on the activity of those two kinases. Meanwhile, pC-HSL-pretreated plants also showed a strong induction of kinase activities of NbSIPK and NbWIPK after TMV inoculation. Taken together, our results demonstrate that pC-HSL treatment increases plant resistance to TMV infection, which is helpful to uncover the outcome of interaction between R. palustris and its host plants.

Single-dose intranasal subunit vaccine rapidly clears secondary sepsis in a high-dose pneumonic plague infection

Yersinia pestis, the causative agent of plague, has killed millions throughout human history. Though public health initiatives have reduced the number of plague cases, it remains endemic in many areas of the world. It also remains a significant threat for use as a biological weapon. Naturally occurring multi-drug antibiotic resistance has been observed in Y. pestis, and resistant strains have been engineered for use as a biological weapon. Vaccines represent our best means of protection against the threat of antibiotic resistant plague. We have developed a vaccine consisting of two Y. pestis virulence factors, LcrV (V) and F1, conjugated to Tobacco Mosaic Virus (TMV), a safe, non-replicating plant virus that can be administered mucosally, providing complete protection against pneumonic plague, the deadliest form of the disease and the one most likely to be seen in a biological attack. A single intranasal (i.n.) dose of TMV-F1 + TMV-V (TMV-F1/V) protected 88% of mice against lethal challenge with 100 LD50 of Y. pestis CO92pgm-, while immunization with rF1 + rV without TMV was not protective. Serum and tissues were collected at various timepoints after challenge to assess bacterial clearance, histopathology, cytokine production, and antibody production. Overall, TMV-F1/V immunized mice showed a significant reduction in histopathology, bacterial burden, and inflammatory cytokine production following challenge compared to rF1 + rV vaccinated and unvaccinated mice. Pneumonic challenge resulted in systemic dissemination of the bacteria in all groups, but only TMV-F1/V immunized mice rapidly cleared bacteria from the spleen and liver. There was a direct correlation between pre-challenge serum F1 titers and recovery in all immunized mice, strongly suggesting a role for antibody in the neutralization and/or opsonization of Y. pestis in this model. Mucosal administration of a single dose of a Y. pestis TMV-based subunit vaccine, without any additional adjuvant, can effectively protect mice from lethal infection.

WY195, a New Inducible Promoter From the Rubber Powdery Mildew Pathogen, Can Be Used as an Excellent Tool for Genetic Engineering.

Until now, there are few studies and reports on the use of endogenous promoters of obligate biotrophic fungi. The WY195 promoter in the genome of Oidium heveae, the rubber powdery mildew pathogen, was predicted using PromoterScan and its promoter function was verified by the transient expression of the β-glucuronidase (GUS) gene. WY195 drove high levels of GUS expression in dicotyledons and monocotyledons. qRT-PCR indicated that GUS expression regulated by the WY195 promoter was 17.54-fold greater than that obtained using the CaMV 35S promoter in dicotyledons (Nicotiana tabacum), and 5.09-fold greater than that obtained using the ACT1 promoter in monocotyledons (Oryza sativa). Furthermore, WY195-regulated GUS gene expression was induced under high-temperature and drought conditions. Soluble proteins extracted from WY195-hpaXm transgenic tobacco was bioactive. Defensive micro-HR induced by the transgene expression of hpaXm was observed on transgenic tobacco leaves. Disease resistance bioassays showed that WY195-hpaXm transgenic tobacco enhanced the resistance to tobacco mosaic virus (TMV). WY195 has great potential for development as a new tool for genetic engineering. Further in-depth studies will help to better understand the transcriptional regulation mechanisms and the pathogenic mechanisms of O. heveae.

Treatment of Penicillium chrysogenum extracts (PDMP) restricts the spread of Tobacco mosaic virus by priming callose deposition in Nicotiana benthamiana

Plants are often primed to enhanced resistance upon recognizing certain microbes and microbial metabolites/molecules. We investigated the effect of PDMP, the peptides extract of dry mycelia of Penicillium chrysogenum, on defense of Nicotiana benthamiana to Tobacco mosaic virus (TMV). The 30B vector harboring the green fluorescent protein gene (30B:GFP) was used to monitor virus movement. Movement of the virus vector was limitied in PDMP-pretreated tobacco, in which significant callose accumulation was observed after challenge inoculation with the TMV vector. Callose accumulation was absent in plants pretreated with both the PDMP and callose synthesis inhibitor, resulting in elimination of PDMP-induced inhibition of TMV spread. Transcripts of the defense-related genes were significantly accumulated after challenge inoculation with TMV in PDMP-pretreated tobacco. Interestingly, PDMP treatment or TMV inoculation alone did neither induce callose deposition, nor enhance the transcript abundance of the defense-related genes, indicating that PDMP was more likely to promote tobacco to a primed state than induce defense responses directly. The primed callose accumulation plays a crucial role in restricting TMV spread in PDMP-pretreated tobacco. The present results provide evidence of PDMP can promote N. benthamiana to a primed state of enhance defense against TMV.

A step towards Balkan Capsicum annuum L. core collection: Phenotypic and biochemical characterization of 180 accessions for agronomic, fruit quality, and virus resistance traits.

Region-specific local landraces represent a germplasm diversity adapted and acclimatized to local conditions, and are ideal to breed for targeted market niches while maintaining the variability of heirloom traits. A collection of 180 pepper accessions, collected from 62 diverse locations across six Balkan countries, were characterized and evaluated for phenotypic and biochemical variation during a multi-year environment. An assortment of 32 agro-morphological, fruit quality, and virus resistance traits were evaluated, and the top 10% accessions were identified. A wide range of trait variation concerning plant architecture, inflorescence and fruit traits, yield and fruit quality was observed, and appreciable variation was noticed. According to hierarchical clustering, six distinct clusters were established based on pre-defined varietal groups. Divergence among accessions for phenotypic and fruit compositional variability was analyzed, and eight principal components were identified that contributed ~71% of the variation, with fruit shape, width, wall thickness, weight, and fruit quality traits being the most discriminant. Evaluation of the response to tobacco mosaic virus (TMV) and pepper mild mottle mosaic virus (PMMoV) showed that 24 and 1 accession were resistant, respectively while no tomato spotted wilt virus (TSWV) resistance was found. Considerable diversity for agro-bio-morphological traits indicates the Balkan pepper collection as good gene sources for pre-breeding and cultivar development that are locally adapted.