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Summary Pathogenesis‐related (PR) proteins are induced by abiotic and biotic stresses and generally considered as part of the plant defense mechanism. However, it remains yet largely unclear if and how they are involved in virus infection. Our recent quantitative, comparative proteomic study identified three PR‐5 family proteins that are significantly differentially accumulated in the plasmodesmata (PD)‐enriched fraction isolated from Nicotiana benthamiana leaves infected by turnip mosaic virus (TuMV). In this study, we employed the TuMV‐Arabidopsis pathosystem to characterize the involvement of two Arabidopsis orthologs, AtOSM34 and AtOLP of the three N. benthamiana PR‐5‐like proteins. We show that AtOSM34 and AtOLP are PD‐localized proteins and their expression is up‐ and downregulated in response to TuMV infection, respectively. Deficiency or overexpression of AtOLP does not affect viral RNA accumulation. Knockdown of AtOSM34 inhibits TuMV infection, whereas its overexpression promotes viral infection. We further demonstrate that AtOSM34 functions as a proviral factor through diminishing PD callose deposition to promote viral intercellular movement, targeting the viral replication complex to enhance viral replication, and suppressing the ROS‐mediated antiviral response. Taken together, these data suggest that TuMV has evolved the ability to selectively upregulate and subvert AtOSM34, a PR‐5 family protein to assist its infection. [ABSTRACT FROM AUTHOR]

Aphid-transmitted viruses cause significant losses in pepper production worldwide, negatively affecting yield and quality. The emergence of new aphid-transmitted viruses or development of variants as well as the occurrence in mixed infections make management a challenge. Here, we overview the current status of the distribution, incidence and phylogeny of aphids and the viruses they transmit in pepper in Africa; outline the available genetic resources, including sources of resistance, resistance genes and molecular markers; and discuss the recent advances in understanding the genetic basis of resistance to the predominant African viruses infecting pepper. Pepper veinal mottle virus (PVMV; Potyvirus); Potato virus Y (PVY; Potyvirus), Chili veinal mottle virus (ChiVMV; Potyvirus), Cucumber mosaic virus (CMV; Cucumovirus) and Pepper veins yellow virus (PeVYV; Polerovirus) have been reported to be the most widespread and devastating aphid-transmitted viruses infecting pepper across Africa. Co-infection or mixed infection between aphid-transmitted viruses has been detected and the interrelationship between viruses that co-infect chili peppers is poorly understood. Establishing and evaluating existing and new diversity sets with more genetic diversity is an important component of developing host resistance and implementing integrated management strategies. However, more work needs to be done to characterize the aphid-transmitted viral strains across Africa and understand their phylogeny in order to develop more durable host resistance. In addition, a limited number of QTLs associated with resistance to the aphid-transmitted virus have been reported and QTL data are only available for PVY, ChiVMV and CMV mainly against European and Asian strains, although PVMV is likely the most important aphid-transmitted viral disease in Africa. There is a need to identify germplasm resources with resistance against various aphid-transmitted virus strains, and subsequent pyramiding of the resistance using marker-assisted selection could be an effective strategy. The recent advances in understanding the genetic basis of the resistance to the virus and the new breeding techniques that can be leveraged to accelerate breeding for aphid-transmitted virus in pepper are proposed as strategies to more efficiently develop resistant cultivars. The deployment of multi-genetic resistances in pepper is an effective and desirable method of managing viral-diseases in Africa and limit losses for farmers in a sustainable manner. [ABSTRACT FROM AUTHOR]

Positive‐sense RNA viruses remodel cellular cytoplasmic membranes as the membranous sources for the formation of viral replication organelles (VROs) for viral genome replication. In plants, they traffic through plasmodesmata (PD), plasma membrane‐lined pores enabling cytoplasmic connections between cells for intercellular movement and systemic infection. In this study, we employed turnip mosaic virus (TuMV), a plant RNA virus to investigate the involvement of RTNLB3 and RTNLB6, two ER (endoplasmic reticulum) membrane‐bending, PD‐located reticulon‐like (RTNL) non‐metazoan group B proteins (RTNLBs) in viral infection. We show that RTNLB3 interacts with TuMV 6K2 integral membrane protein and RTNLB6 binds to TuMV coat protein (CP). Knockdown of RTNLB3 promoted viral infection, whereas downregulation of RTNLB6 restricted viral infection, suggesting that these two RTNLs play contrasting roles in TuMV infection. We further demonstrate that RTNLB3 targets the α‐helix motif 42LRKSM46 of 6K2 to interrupt 6K2 self‐interactions and compromise 6K2‐induced VRO formation. Moreover, overexpression of AtRTNLB3 apparently promoted the selective degradation of the ER and ER‐associated protein calnexin, but not 6K2. Intriguingly, mutation of the α‐helix motif of 6K2 that is required for induction of VROs severely affected 6K2 stability and abolished TuMV infection. Thus, RTNLB3 attenuates TuMV replication, probably through the suppression of 6K2 function. We also show that RTNLB6 promotes viral intercellular movement but does not affect viral replication. Therefore, the proviral role of RTNLB6 is probably by enhancing viral cell‐to‐cell trafficking. Taken together, our data demonstrate that RTNL family proteins may play diverse complex, even opposite, roles in viral infection in plants. [ABSTRACT FROM AUTHOR]

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

Introduction: Canola (Brassica napus L.) is one of the most important crops worldwide. Turnip yellows virus (TuYV), transmitted by aphids, is one of the most damaging viruses affecting canola crops and is challenging to control. With the prediction of more intense and prolonged drought events due to future climate change, an additional factor may extensively impact the epidemiology of plant diseases. This study aimed to understand the impact of drought on canola plants infected with TuYV and to explore the relationship between virus infection and drought. Methods: Two glasshouse experiments were conducted: 1. Competition: Four plants (two infected, two non-infected) were grown in the same pot. 2. No Competition: One plant was grown per pot. In both experiments, infected and non-infected canola plants were exposed to well-watered conditions, water stress (simulated drought), and terminal drought. Various plant traits were recorded, including biomass, leaf area, height, number of leaves, chlorophyll content, water use efficiency, and virus symptom expression. Results: Both virus infection and water stress reduced dry biomass, leaf area, and height. Virus infection alone reduced canola biomass by up to 49% compared to non-infected, well-watered controls. Under water stress or terminal drought, the biomass of TuYV-infected plants was further reduced by up to 71% and 65%, respectively. Virus infection also reduced the number of leaves, although water treatment alone did not. Chlorophyll content was higher in water-stressed and terminal drought plants compared to well-watered ones, while virus infection reduced chlorophyll content. The impact of drought and virus infection was more pronounced when plants were under competition. Discussion: Given the expected increase in prolonged and frequent droughts in many canola-growing regions due to climate change, a significant detrimental effect on canola production due to the combined influence of drought and TuYV is anticipated. This study underscores the need for developing mitigation strategies to protect canola production in a changing climate. [ABSTRACT FROM AUTHOR]

Potyvirus diseases are one of the main challenges facing the production of yam (Dioscorea spp.). The objective of this study was to identify the potyviruses present in the Dioscorea spp. germplasm collection at Instituto de Investigaciones de Viandas Tropicales (INIVIT) to establish methodologies for the characterization of the associated diseases. For this purpose, immunochemical and molecular methods were used to identify the potyviruses present. The symptomatology of Dioscorea spp. at INIVIT's germplasm collection was described. In addition, the severity and incidence in the germplasm collection and production areas were evaluated. As a result, the first report of yam mosaic virus (Potyvirus yamtesselati) and yam mild mosaic virus (Potyvirus yamplacidum) in Cuba is presented. The existence of resistant, tolerant, and susceptible cultivars to potyvirus-associated diseases in the germplasm collection was detected, and the incidence of these diseases was higher than 64% in the production areas evaluated. This study represents a step forward in the establishment of certification programs for propagating material of Dioscorea spp. in Cuba. [ABSTRACT FROM AUTHOR]

Nine viruses of the bean common mosaic virus subgroup of potyviruses are major international crop pathogens, but their phylogenetically closest relatives from non-crop plants have mostly been found only in SE Asia and Oceania, which is thus likely to be their "centre of emergence". We have compared over 700 of the complete genomic ORFs of the crop pandemic and the non-crop viruses in various ways. Only one-third of crop virus genomes are non-recombinant, but more than half the non-crop virus genomes are. Four of the viruses were from crops domesticated in the Old World (Africa to SE Asia), and the other five were from New World crops. There was a temporal signal in only three of the crop virus datasets, but it confirmed that the most recent common ancestors of all the crop viruses were before inter-continental marine trade started after 1492 CE, whereas all the crown clusters of the phylogenies are from after that date. The non-crop virus datasets are genetically more diverse than those of the crop viruses, and Tajima's D analyses showed that their populations were contracting, and only one of the crop viruses had a significantly expanding population. dN/dS analyses showed that most of the genes and codons in all the viruses were under significant negative selection, and the few that were under significant positive selection were mostly in the PIPO-encoding region of the P3 protein, or the PIPO protein itself. Interestingly, more positively selected codons were found in non-crop than in crop viruses, and, as the hosts of the former were taxonomically more diverse than the latter, this may indicate that the positively selected codons are involved in host range determination; AlphaFold3 modelling was used to investigate this possibility. [ABSTRACT FROM AUTHOR]

A study conducted in Montecillo, Texcoco, Mexico, identified two viruses associated with symptoms of viral diseases in bean crops. The detected viruses were Orthotospovirus impatiensnecromaculae and two isolates of Potyvirus phaseoluteum. These viruses present significant differences from other viruses reported in different plant species. This finding highlights the importance of accurate identification for the management and control of these viral infections in bean crops in Mexico. [Extracted from the article]

East Asian Passiflora virus (EAPV) causes passionfruit woodiness disease, a major threat limiting passionfruit production in eastern Asia, including Taiwan and Vietnam. In this study, an infectious cDNA clone of a Taiwanese severe isolate EAPV-TW was tagged with a green fluorescent protein (GFP) reporter to monitor the virus in plants. Nicotiana benthamiana and yellow passionfruit plants inoculated with the construct showed typical symptoms of EAPV-TW. Based on our previous studies on pathogenicity determinants of potyviral HC-Pros, a deletion of six amino acids (d6) alone and its association with a point mutation (F8I, simplified as I8) were conducted in the N-terminal region of the HC-Pro gene of EAPV-TW to generate mutants of EAPV-d6 and EAPV-d6I8, respectively. The mutant EAPV-d6I8 caused infection without conspicuous symptoms in N. benthamiana and yellow passionfruit plants, while EAPV-d6 still induced slight leaf mottling. EAPV-d6I8 was stable after six passages under greenhouse conditions and displayed a zigzag pattern of virus accumulation, typical of a beneficial protective virus. The cross-protection effectiveness of EAPV-d6I8 was evaluated in both N. benthamiana and yellow passionfruit plants under greenhouse conditions. EAPV-d6I8 conferred complete cross-protection (100%) against the wild-type EAPV-TW-GFP in both N. benthamiana and yellow passionfruit plants, as verified by no severe symptoms, no fluorescent signals, and PCR-negative status for GFP. Furthermore, EAPV-d6I8 also provided complete protection against Vietnam's severe strain EAPV-GL1 in yellow passionfruit plants. Our results indicate that the attenuated mutant EAPV-d6I8 has great potential to control EAPV in Taiwan and Vietnam via cross-protection. [ABSTRACT FROM AUTHOR]

Background: Pepper veinal mottle virus (PVMV) belongs to the genus Potyvirus within the family Potyviridae and is a major threat to pepper production, causing reduction in yield and fruit quality; however, efficient pesticides and chemical treatments for plant protection against viral infections are lacking. Hence, there is a critical need to discover highly active and environment-friendly antiviral agents derived from natural sources. Bacillus spp. are widely utilized as biocontrol agents to manage fungal, bacterial, and viral plant diseases. Particularly, Bacillus velezensis HN-2 exhibits a strong antibiotic activity against plant pathogens and can also induce plant resistance. Methods: The experimental subjects employed in this study were Bacillus velezensis HN-2, benzothiadiazole, and dufulin, aiming to evaluate their impact on antioxidant activity, levels of reactive oxygen species, activity of defense enzymes, and expression of defense-related genes in Nicotiana benthamiana. Furthermore, the colonization ability of Bacillus velezensis HN-2 in Capsicum chinense was investigated. Results: The results of bioassays revealed the robust colonization capability of Bacillus velezensis HN-2, particularly in intercellular spaces, leading to delayed infection and enhanced protection against PVMV through multiple plant defense mechanisms, thereby promoting plant growth. Furthermore, Bacillus velezensis HN-2 increased the activities of antioxidant enzymes, thereby mitigating the PVMV-induced ROS production in Nicotiana benthamiana. Moreover, the application of Bacillus velezensis HN-2 at 5 dpi significantly increased the expression of JA-responsive genes, whereas the expression of salicylic acidresponsive genes remained unchanged, implying the activation of the JA signaling pathway as a crucial mechanism underlying Bacillus velezensis HN-2-induced anti-PVMV activity. Immunoblot analysis revealed that HN-2 treatment delayed PVMV infection at 15 dpi, further highlighting its role in inducing plant resistance and promoting growth and development. Conclusions: These findings underscore the potential of Bacillus velezensis HN-2 for field application in managing viral plant diseases effectively. [ABSTRACT FROM AUTHOR]

Plant viruses cause severe losses in agricultural production. Parasite-derived resistance (PDR) offers a promising avenue for developing disease-resistant varieties independent of resistance genes. However, for potyviruses with great agricultural importance, such as soybean mosaic virus (SMV), systematic research on viral genes that can be used for PDR has not been conducted. In this study, we transiently expressed the untranslated region (UTR) or each protein-coding cistron of SMV in Nicotiana benthamiana to evaluate their potential role in conferring PDR. A viral suppressor of RNA silencing (VSR) was also applied to investigate the possible mechanisms of the PDR. The results showed that the transient overexpression of UTR and each cistron of SMV could inhibit SMV infection. The expression of VSR in N. benthamiana leaves could compromise UTR and most of the SMV cistron-mediated inhibition of SMV infection, indicating the involvement of RNA silencing in PDR. In comparison, the expression of VSR could not compromise the PDR conferred by coat protein (CP), P3N-PIPO, cylindrical inclusion (CI), and NIa-Pro, suggesting that these viral cistrons may play roles in PDR at the protein level. These results reveal diverse mechanisms in PDR conferred by different viral cistrons and provide potential gene candidates that can be used for transgenic approaches against SMV. [ABSTRACT FROM AUTHOR]

BackgroundDisporopsis, a member of the Liliaceae family and a perennial herb, is predominantly cultivated in southwestern and southeastern China. Its rhizome, referred to as Zhugenqi, serves as a traditional Chinese medicinal herb for the treatment of bone injuries. However, viral diseases have emerged as a significant challenge in the cultivation of Disporopsis.ObjectiveThe aim of this study was to identify and characterize viruses present in diseased samples of Disporopsis spp. using high-throughput sequencing (HTS) and reverse transcription-polymerase chain reaction (RT-PCR) to enhance the understanding of the virome associated with Disporopsis and to inform diagnostic and control strategies for viral diseases in this plant.MethodsDiseased samples of Disporopsis spp. were subjected to HTS and RT-PCR for virus identification. A total of five viruses were detected, including three novel viruses and two known viruses. The novel viruses were provisionally named Disporopsis chlorotic stripe virus (DCSV), Disporopsis pernyi-associated partitivirus (DaPTV), and Disporopsis pernyi-associated lispi-like virus (DaLV). Sequence identity and phylogenetic analyses were performed to confirm the novelty and taxonomic placement of these viruses.ResultsDCSV exhibited polyprotein sequence identities ranging from 47.6% to 83.6% with other potyviruses, with the highest identity (83.6%) shared with Polygonatum kingianum virus 5 (PKgV5). DaLV shared an amino acid sequence identity of 34.59% with maize suscal virus (MSV), and DaPTV shared an identity of 76.18–85.10% with Paris alphapartitivirus (ParAPV). Phylogenetic analyses supported the potential classification of the three novel viruses as new members of their respective genera. Two isolates of polygonatum mosaic-associated virus 1 (PMaV1) were identified in Disporopsis for the first time, showing divergences of 96.33% and 98.86% from existing isolates. RT-PCR analysis of 67 Disporopsis field samples collected from four cities in China revealed that more than half of the samples tested positive for at least one of the five viruses. PMaV1 and DaLV were the most prevalent, detected in 22 and 34 out of the 67 samples, respectively. Other viruses were detected at low rates and/or had limited distribution.ConclusionThis study provides insights into the virome infecting Disporopsis and offers valuable information for the diagnosis and control of viral diseases in this plant. The identification of five viruses, including three potential new members of their respective genera, contributes to the understanding of the viral threats to Disporopsis cultivation.

Aphid-transmitted viruses cause significant losses in pepper production worldwide, negatively affecting yield and quality. The emergence of new aphid-transmitted viruses or development of variants as well as the occurrence in mixed infections make management a challenge. Here, we overview the current status of the distribution, incidence and phylogeny of aphids and the viruses they transmit in pepper in Africa; outline the available genetic resources, including sources of resistance, resistance genes and molecular markers; and discuss the recent advances in understanding the genetic basis of resistance to the predominant African viruses infecting pepper. Pepper veinal mottle virus (PVMV; Potyvirus); Potato virus Y (PVY; Potyvirus), Chili veinal mottle virus (ChiVMV; Potyvirus), Cucumber mosaic virus (CMV; Cucumovirus) and Pepper veins yellow virus (PeVYV; Polerovirus) have been reported to be the most widespread and devastating aphid-transmitted viruses infecting pepper across Africa. Co-infection or mixed infection between aphid-transmitted viruses has been detected and the interrelationship between viruses that co-infect chili peppers is poorly understood. Establishing and evaluating existing and new diversity sets with more genetic diversity is an important component of developing host resistance and implementing integrated management strategies. However, more work needs to be done to characterize the aphid-transmitted viral strains across Africa and understand their phylogeny in order to develop more durable host resistance. In addition, a limited number of QTLs associated with resistance to the aphid-transmitted virus have been reported and QTL data are only available for PVY, ChiVMV and CMV mainly against European and Asian strains, although PVMV is likely the most important aphid-transmitted viral disease in Africa. There is a need to identify germplasm resources with resistance against various aphid-transmitted virus strains, and subsequent pyramiding of the resistance using marker-assisted selection could be an effective strategy. The recent advances in understanding the genetic basis of the resistance to the virus and the new breeding techniques that can be leveraged to accelerate breeding for aphid-transmitted virus in pepper are proposed as strategies to more efficiently develop resistant cultivars. The deployment of multi-genetic resistances in pepper is an effective and desirable method of managing viral-diseases in Africa and limit losses for farmers in a sustainable manner.

IntroductionCanola (Brassica napus L.) is one of the most important crops worldwide. Turnip yellows virus (TuYV), transmitted by aphids, is one of the most damaging viruses affecting canola crops and is challenging to control. With the prediction of more intense and prolonged drought events due to future climate change, an additional factor may extensively impact the epidemiology of plant diseases. This study aimed to understand the impact of drought on canola plants infected with TuYV and to explore the relationship between virus infection and drought.MethodsTwo glasshouse experiments were conducted: 1. Competition: Four plants (two infected, two non-infected) were grown in the same pot. 2. No Competition: One plant was grown per pot. In both experiments, infected and non-infected canola plants were exposed to well-watered conditions, water stress (simulated drought), and terminal drought. Various plant traits were recorded, including biomass, leaf area, height, number of leaves, chlorophyll content, water use efficiency, and virus symptom expression.ResultsBoth virus infection and water stress reduced dry biomass, leaf area, and height. Virus infection alone reduced canola biomass by up to 49% compared to non-infected, well-watered controls. Under water stress or terminal drought, the biomass of TuYV-infected plants was further reduced by up to 71% and 65%, respectively. Virus infection also reduced the number of leaves, although water treatment alone did not. Chlorophyll content was higher in water-stressed and terminal drought plants compared to well-watered ones, while virus infection reduced chlorophyll content. The impact of drought and virus infection was more pronounced when plants were under competition.DiscussionGiven the expected increase in prolonged and frequent droughts in many canola-growing regions due to climate change, a significant detrimental effect on canola production due to the combined influence of drought and TuYV is anticipated. This study underscores the need for developing mitigation strategies to protect canola production in a changing climate.

Papaver somniferum L. produces therapeutically-useful alkaloids like morphine, codeine, papaverine, and thebaine that accumulate in the latex of its capsule. Apart from its alkaloids, the edible seeds of the plant have high nutritional value and culinary use, with the seed oil being rich in the health-promoting unsaturated fatty acids. Sujata is low alkaloid-producing latex-less culinary variety of P. somniferum developed from an alkaloid-rich gum harvest parent (Sampada) for curtailing the narcotic menace of morphine and opium (dried latex). Earlier, it has been shown that the expression of stearoyl-acyl-carrier protein desaturase (PsSAD) in the young capsule and the proportion of unsaturated fatty acids in the seeds are higher in Sujata as compared to Sampada. Here, we studied bacterial endophytes isolated from Sujata tissues for their role in defining the fatty acid (saturated stearic versus unsaturated oleic) profile in its leaves and seeds. Besides, a potyvirus infecting P. somniferum was characterized through its coat protein gene sequencing and transmission electron microscopy and the two genotypes (Sujata and Sampada) contrasting in their phenotypes (oil/fatty acid, alkaloid and latex profiles) were compared for their susceptibility towards it through indicator plant- and qRT-PCR-based virus infectivity assays. In both the assays, Sujata was found to have higher susceptibility to the potyvirus, as compared to Sampada. The most plausible reason for this could be the higher PsSAD expression in the leaves of Sujata, which resulted in higher relative levels of oleic acid and lower relative levels of stearic acid in its leaves as compared to that of Sampada.

Abstract Background Plant responses to a wide range of stresses are known to be regulated by epigenetic mechanisms. Pathogen-related investigations, particularly against RNA viruses, are however scarce. It has been demonstrated that Arabidopsis thaliana plants defective in some members of the RNA-directed DNA methylation (RdDM) or histone modification pathways presented differential susceptibility to the turnip mosaic virus. In order to identify genes directly targeted by the RdDM-related RNA Polymerase V (POLV) complex and the histone demethylase protein JUMONJI14 (JMJ14) during infection, the transcriptomes of infected mutant and control plants were obtained and integrated with available chromatin occupancy data for various epigenetic proteins and marks. Results A comprehensive list of virus-responsive gene candidates to be regulated by the two proteins was obtained. Twelve genes were selected for further characterization, confirming their dynamic regulation during the course of infection. Several epigenetic marks on their promoter sequences were found using in silico data, raising confidence that the identified genes are actually regulated by epigenetic mechanisms. The altered expression of six of these genes in mutants of the methyltransferase gene CURLY LEAF and the histone deacetylase gene HISTONE DEACETYLASE 19 suggests that some virus-responsive genes may be regulated by multiple coordinated epigenetic complexes. A temporally separated multiple plant virus infection experiment in which plants were transiently infected with one virus and then infected by a second one was designed to investigate the possible roles of the identified POLV- and JMJ14-regulated genes in wild-type (WT) plants. Plants that had previously been stimulated with viruses were found to be more resistant to subsequent virus challenge than control plants. Several POLV- and JMJ14-regulated genes were found to be regulated in virus induced resistance in WT plants, with some of them poisoned to be expressed in early infection stages. Conclusions A set of confident candidate genes directly regulated by the POLV and JMJ14 proteins during virus infection was identified, with indications that some of them may be regulated by multiple epigenetic modules. A subset of these genes may also play a role in the tolerance of WT plants to repeated, intermittent virus infections.

The movement of potyviruses, the largest genus of single‐stranded, positive‐sense RNA viruses responsible for serious diseases in crops, is very complex. As potyviruses developed strategies to hijack the host secretory pathway and plasmodesmata (PD) for their transport, the goal of this study was to identify membrane and/or PD‐proteins that interact with the 6K2 protein, a potyviral protein involved in replication and cell‐to‐cell movement of turnip mosaic virus (TuMV). Using split‐ubiquitin membrane yeast two‐hybrid assays, we screened an Arabidopsis cDNA library for interactors of TuMV6K2. We isolated AtHVA22a (Hordeum vulgare abscisic acid responsive gene 22), which belongs to a multigenic family of transmembrane proteins, homologous to Receptor expression‐enhancing protein (Reep)/Deleted in polyposis (DP1)/Yop1 family proteins in animal and yeast. HVA22/DP1/Yop1 family genes are widely distributed in eukaryotes, but the role of HVA22 proteins in plants is still not well known, although proteomics analysis of PD fractions purified from Arabidopsis suspension cells showed that AtHVA22a is highly enriched in a PD proteome. We confirmed the interaction between TuMV6K2 and AtHVA22a in yeast, as well as in planta by using bimolecular fluorescence complementation and showed that TuMV6K2/AtHVA22a interaction occurs at the level of the viral replication compartment during TuMV infection. Finally, we showed that the propagation of TuMV is increased when AtHVA22a is overexpressed in planta but slowed down upon mutagenesis of AtHVA22a by CRISPR‐Cas9. Altogether, our results indicate that AtHVA22a plays an agonistic effect on TuMV propagation and that the C‐terminal tail of the protein is important in this process. [ABSTRACT FROM AUTHOR]

Tomato (Solanum lycopersicum) is the most important vegetable and fruit crop in the family Solanaceae worldwide. Numerous pests and pathogens, especially viruses, severely affect tomato production, causing immeasurable market losses. In Taiwan, the cultivation of tomato crops is mainly threatened by insect-borne viruses, among which pepper veinal mottle virus (PVMV) is one of the most prevalent. PVMV is a member of the genus Potyvirus of the family Potyviridae and is non-persistently transmitted by aphids. Its infection significantly reduces tomato fruit yield and quality. So far, no PVMV-resistant tomato lines are available. In this study, we performed nitrite-induced mutagenesis of the PVMV tomato isolate Tn to generate attenuated PVMV mutants. PVMV Tn causes necrotic lesions in Chenopodium quinoa leaves and severe mosaic and wilting in Nicotiana benthamiana plants. After nitrite treatment, three attenuated PVMV mutants, m4-8, m10-1, and m10-11, were selected while inducing milder responses to C. quinoa and N. benthamiana with lower accumulation in tomato plants. In greenhouse tests, the three mutants showed different degrees of cross-protection against wild-type PVMV Tn. m4-8 showed the highest protective efficacy against PVMV Tn in N. benthamiana and tomato plants, 100% and 97.9%, respectively. A whole-genome sequence comparison of PVMV Tn and m4-8 revealed that 20 nucleotide substitutions occurred in the m4-8 genome, resulting in 18 amino acid changes. Our results suggest that m4-8 has excellent potential to protect tomato crops from PVMV. The application of m4-8 in protecting other Solanaceae crops, such as peppers, will be studied in the future. [ABSTRACT FROM AUTHOR]

Introduction/Objective. Ayocote bean (Phaseolus coccineus) has potential as a source of resistance in breeding programs because it exhibits greater tolerance to plant pathogens than P. vulgaris. However, its sanitary characterization is insipient; therefore, the purpose of this work was to carry out an etiological-epidemiological diagnosis, with emphasis on presumptive symptoms of viral and phytoplasmic organisms, and a typical fungal signs of powdery mildew. Materials and Methods: A plot (50 x 62 m) of flowering Ayocote bean was selected. It was divided into 80 (8 x 10) quadrats (6 x 6 m) and 720 subquadrats (2 x 2 m). From 25 plants with powdery-mildew-type leaf symptoms, mycelium was collected with adhesive tape for light microscopy observation and taxonomic identification. Length-width measurements were made on 60 conidia. Pure mycelium collected in situ and ex situ from 1-5 leaflets/plant was used for genomic analysis by PCR with universal primers ITS1 and ITS4. Samples were sequenced in Macrogen Inc. Korea. A total of 63 plants and 121 trifoliate leaves with viral and phytoplasmic symptoms were collected by direct sampling. In 88/121 samples, genomic analysis was performed by PCR with universal primers for Potyvirus (1), Begomovirus (2), and Phytoplasmas (1). Sequence editing and analysis were performed in SeqAssem and BLASTn/GenBank. Phylogenetic constructions were developed in Mega 11 with MUSCLE, Maximum Likelihood (ML), and HKY substitution model (1000-Bootstrap). Putative powdery mildew severity (%), flower damage (%), Macrodactylus sp. adult density, and plant vigor (%) were evaluated in 80 quadrats (3subquadrats/quadrat) with App-Monitor®v1.1 configured with a 5-class scale. In GoldenSurfer® v10, Kriging geostatistical analysis was performed to determine the spatial interrelationship between these variables. Results: Erysiphe vignae was identified as associated with powdery mildew of P. coccineus. The fungus, with hyaline, ovoid to ellipsoid conidia measuring 31.74 ± 0.3419 µm x 15.11 ± 0.1579 µm, without the presence of fibrosin bodies, had 100% genomic homology. This is the first report in Mexico. With average July-August temperature and relative humidity of 16.3 °C (±5.8) and 92.8 % (±10.7), respectively, powdery mildew leaf incidence and severity were 65.3 and 22.7 % (±16.9, range: 0 - 66.5 %), respectively. The most inductive focus (60-80 % severity) had an aggregate e 4-quadrat pattern (96 m2, lag = 4 and s2-s = 450). Inoculum dispersal was significantly associated with dominant North-South winds and plant vigor (lag = 4 and s2-s = 470). Flower damage was inconclusive in its spatial association with powdery mildew and Macrodactylus sp. suggesting uncorrelated events. No Potyvirus, Begomovirus, or Phytoplasmas were detected associated with yellowing, leaf distortion, mosaic, internode shortening, and other symptoms observed in situ. This confirms the relative tolerance/resistance reported for P. coccineus. Conclusion: E. vignae (Erysiphales: Erysiphaceae) associated with P. coccineus is reported for the first time in Mexico with moderate to intense epidemic level, which indicates its susceptible condition to this fungus. However, negative results for Potyvirus, Begomovirus, and Phytoplasmas, validate the apparent tolerance/resistance of P. coccineus to these organisms. [ABSTRACT FROM AUTHOR]

The best-characterized functional motifs of the potyviral Helper-Component protease (HC-Pro) responding for aphid transmission, RNA silencing suppression, movement, symptom development, and replication are gathered in this review. The potential cellular protein targets of plant virus proteases remain largely unknown despite their multifunctionality. The HC-Pro catalytic domain, as a cysteine protease, autoproteolytically cleaves the potyviral polyproteins in the sequence motif YXVG/G and is not expected to act on host targets; however, 146 plant proteins in the Viridiplantae clade containing this motif were searched in the UniProtKB database and are discussed. On the other hand, more than 20 interactions within the entire HC-Pro structure are known. Most of these interactions with host targets (such as the 20S proteasome, methyltransferase, transcription factor eIF4E, and microtubule-associated protein HIP2) modulate the cellular environments for the benefit of virus accumulation or contribute to symptom severity (interactions with MinD, Rubisco, ferredoxin) or participate in the suppression of RNA silencing (host protein VARICOSE, calmodulin-like protein). On the contrary, the interaction of HC-Pro with triacylglycerol lipase, calreticulin, and violaxanthin deepoxidase seems to be beneficial for the host plant. The strength of these interactions between HC-Pro and the corresponding host protein vary with the plant species. Therefore, these interactions may explain the species-specific sensitivity to potyviruses. [ABSTRACT FROM AUTHOR]

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Background: Plant responses to a wide range of stresses are known to be regulated by epigenetic mechanisms. Pathogen-related investigations, particularly against RNA viruses, are however scarce. It has been demonstrated that Arabidopsis thaliana plants defective in some members of the RNA-directed DNA methylation (RdDM) or histone modification pathways presented differential susceptibility to the turnip mosaic virus. In order to identify genes directly targeted by the RdDM-related RNA Polymerase V (POLV) complex and the histone demethylase protein JUMONJI14 (JMJ14) during infection, the transcriptomes of infected mutant and control plants were obtained and integrated with available chromatin occupancy data for various epigenetic proteins and marks. Results: A comprehensive list of virus-responsive gene candidates to be regulated by the two proteins was obtained. Twelve genes were selected for further characterization, confirming their dynamic regulation during the course of infection. Several epigenetic marks on their promoter sequences were found using in silico data, raising confidence that the identified genes are actually regulated by epigenetic mechanisms. The altered expression of six of these genes in mutants of the methyltransferase gene CURLY LEAF and the histone deacetylase gene HISTONE DEACETYLASE 19 suggests that some virus-responsive genes may be regulated by multiple coordinated epigenetic complexes. A temporally separated multiple plant virus infection experiment in which plants were transiently infected with one virus and then infected by a second one was designed to investigate the possible roles of the identified POLV- and JMJ14-regulated genes in wild-type (WT) plants. Plants that had previously been stimulated with viruses were found to be more resistant to subsequent virus challenge than control plants. Several POLV- and JMJ14-regulated genes were found to be regulated in virus induced resistance in WT plants, with some of them poisoned to be expressed in early infection stages. Conclusions: A set of confident candidate genes directly regulated by the POLV and JMJ14 proteins during virus infection was identified, with indications that some of them may be regulated by multiple epigenetic modules. A subset of these genes may also play a role in the tolerance of WT plants to repeated, intermittent virus infections. [ABSTRACT FROM AUTHOR]

Sugarcane mosaic virus (SCMV) (genus, Potyvirus; family, Potyviridae) is widespread, deleterious, and the most damaging pathogen of sugarcane (Saccharum officinarum L. and Saccharum spp.) that causes a substantial barrier to producing high sugarcane earnings. Sugarcane mosaic disease (SCMD) is caused by a single or compound infection of SCMV disseminated by several aphid vectors in a non-persistent manner. SCMV has flexuous filamentous particle of 700–750 nm long, which encapsidated in a positive-sense, single-stranded RNA molecule of 9575 nucleotides. RNA interference (RNAi)-mediated antiviral innate immunity is an evolutionarily conserved key biological process in eukaryotes and has evolved as an antiviral defense system to interfere with viral genomes for controlling infections in plants. The current study aims to analyze sugarcane (Saccharum officinarum L. and Saccharum spp.) locus-derived microRNAs (sof-miRNAs/ssp-miRNAs) with predicted potential for targeting the SCMV +ssRNA-encoded mRNAs, using a predictive approach that involves five algorithms. The ultimate goal of this research is to mobilize the in silico- predicted endogenous sof-miRNAs/ssp-miRNAs to experimentally trigger the catalytic RNAi pathway and generate sugarcane cultivars to evaluate the potential antiviral resistance surveillance ability and capacity for SCMV. Experimentally validated mature sugarcane (S. officinarum, 2n = 8X = 80) and (S. spp., 2n = 100–120) sof-miRNA/ssp-miRNA sequences (n = 28) were downloaded from the miRBase database and aligned with the SCMV genome (KY548506). Among the 28 targeted mature locus-derived sof-miRNAs/ssp-miRNAs evaluated, one sugarcane miRNA homolog, sof-miR159c, was identified to have a predicted miRNA binding site, at nucleotide position 3847 of the SCMV genome targeting CI ORF. To verify the accuracy of the target prediction accuracy and to determine whether the sugarcane sof-miRNA/ssp-miRNA could bind the predicted SCMV mRNA target(s), we constructed an integrated Circos plot. A genome-wide in silico-predicted miRNA-mediated target gene regulatory network was implicated to validate interactions necessary to warrant in vivo analysis. The current work provides valuable computational evidence for the generation of SCMV-resistant sugarcane cultivars. [ABSTRACT FROM AUTHOR]

Analysis of the viromes of three symptomatic Fabaceae plants, i.e., red clover (Trifolium pratense L.), pea (Pisum sativum L.), and common bean (Phaseolus vulgaris L.), using high-throughput sequencing revealed complex infections and enabled the acquisition of complete genomes of a potyvirus, bean yellow mosaic virus (BYMV). Based on phylogenetic analysis, the Slovak BYMV isolates belong to two distinct molecular groups, i.e., VI (isolate FA40) and XI (isolates DAT, PS2). Five commercial pea genotypes (Alderman, Ambrosia, Gloriosa, Herkules, Senator) were successfully infected with the BYMV-PS2 inoculum and displayed similar systemic chlorotic mottling symptoms. Relative comparison of optical density values using semi-quantitative DAS-ELISA revealed significant differences among virus titers in one of the infected pea genotypes (Ambrosia) when upper fully developed leaves were tested. Immunoblot analysis of systemically infected Alderman plants showed rather uneven virus accumulation in different plant parts. The lowest virus accumulation was repeatedly detected in the roots, while the highest was in the upper part of the plant stem. [ABSTRACT FROM AUTHOR]

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ABSTRACT Potato virus Y (PVY) is recognized as one of the most common and destructive pathogens seriously affecting potato producing areas worldwide. More recently PVYNTN and PVYN:O/N-Wi, have emerged as the main strains present in the PVY infected plants detected in Brazilian potato fields. In this study, samples of potato collected in south part of Minas Gerais - Brazil were first tested by DAS-ELISA and then by RT-PCR multiplex in order to discriminate the PVY strains. Afterward, part of them was tested by RT-qPCR to confirm and quantify the viruses in infected tissues. The sensitivity of the techniques for detecting PVY isolates present in the sampled locations was investigated, as well as the occurrence of mixed infections, aiming to understand the general epidemiological picture of this pathogen in potato producing fields. In the multiplex RT-PCR test, the samples with O and N serotypes were identified as infected with PVYNTN and PVYN:O/N-Wi strains. When tested by RT-PCR for amplification of PVYE, 41 samples (67,2%) were positive, having a characteristic electrophoretic profile for this recombinant strain, and 9 isolates were also observed with atypical patterns for recombinant PVYE. The best technique to detect mixed infection was RT-qPCR, with the concentration of PVYNTN being much higher than that of PVYN:O/N-Wi. These results show the importance of using the most suitable method for the diagnosis and surveying of PVY strains in crop fields and reveal, for the first time, the dissemination of PVYE recombinants to several Brazilian potato fields.

El cultivo de maracuyá amarillo es afectado por múltiples problemas fitosanitarios. Entre los principales, están los virus de los géneros Potyvirus (soybean mosaic virus, SMV), Cucumovirus (cucumber mosaic virus, CMV), Tymovirus (passion fruit yellow mosaic virus, PFYMV) y Begomovirus (passionfruit leaf distortion virus, PLDV). Información acerca de la prevalencia e interacción entre estos virus es escasa. El objetivo del presente estudio fue verificar la prevalencia e identificar los tipos de infecciones virales mixtas de potyvirus, cucumovirus, tymovirus y begomovirus en cultivos de maracuyá en Valle del Cauca, Colombia. Muestras foliares de maracuyá con síntomas virales fueron recolectadas y se purificaron sus ácidos nucleicos. La identificación de los virus se realizó por PCR empleando cebadores universales por género viral, y cebadores específicos para los virus SMV, CMV, PFYMV y PLDV. Se analizó la incidencia de cada virus por municipio y se comparó la severidad de los síntomas con el diagnóstico realizado. En total se colectaron 66 muestras en los municipios de Toro, Dagua, Roldanillo, Bolívar, La Unión y El Cerrito. Se estableció que los virus con mayor prevalencia fueron PLDV, seguido por SMV y CMV. No se detectó la presencia de PFYMV en las muestras analizadas. Se identificó por primera vez la presencia de infecciones dobles y triples entre potyvirus, cucumovirus y begomovirus, encontrándose mayor severidad de síntomas a mayor número de virus identificado por muestra. La presente investigación provee resultados clave para el diseño de estrategias de control de enfermedades virales en maracuyá.

Sugarcane mosaic virus (SCMV) (genus, Potyvirus; family, Potyviridae) is widespread, deleterious, and the most damaging pathogen of sugarcane (Saccharum officinarum L. and Saccharum spp.) that causes a substantial barrier to producing high sugarcane earnings. Sugarcane mosaic disease (SCMD) is caused by a single or compound infection of SCMV disseminated by several aphid vectors in a non-persistent manner. SCMV has flexuous filamentous particle of 700–750 nm long, which encapsidated in a positive-sense, single-stranded RNA molecule of 9575 nucleotides. RNA interference (RNAi)-mediated antiviral innate immunity is an evolutionarily conserved key biological process in eukaryotes and has evolved as an antiviral defense system to interfere with viral genomes for controlling infections in plants. The current study aims to analyze sugarcane (Saccharum officinarum L. and Saccharum spp.) locus-derived microRNAs (sof-miRNAs/ssp-miRNAs) with predicted potential for targeting the SCMV +ssRNA-encoded mRNAs, using a predictive approach that involves five algorithms. The ultimate goal of this research is to mobilize the in silico- predicted endogenous sof-miRNAs/ssp-miRNAs to experimentally trigger the catalytic RNAi pathway and generate sugarcane cultivars to evaluate the potential antiviral resistance surveillance ability and capacity for SCMV. Experimentally validated mature sugarcane (S. officinarum, 2n = 8X = 80) and (S. spp., 2n = 100–120) sof-miRNA/ssp-miRNA sequences (n = 28) were downloaded from the miRBase database and aligned with the SCMV genome (KY548506). Among the 28 targeted mature locus-derived sof-miRNAs/ssp-miRNAs evaluated, one sugarcane miRNA homolog, sof-miR159c, was identified to have a predicted miRNA binding site, at nucleotide position 3847 of the SCMV genome targeting CI ORF. To verify the accuracy of the target prediction accuracy and to determine whether the sugarcane sof-miRNA/ssp-miRNA could bind the predicted SCMV mRNA target(s), we constructed an integrated Circos plot. A genome-wide in silico-predicted miRNA-mediated target gene regulatory network was implicated to validate interactions necessary to warrant in vivo analysis. The current work provides valuable computational evidence for the generation of SCMV-resistant sugarcane cultivars.

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

Potyvirus diseases are one of the main challenges facing the production of yam (Dioscorea spp.). The objective of this study was to identify the potyviruses present in the Dioscorea spp. germplasm collection at Instituto de Investigaciones de Viandas Tropicales (INIVIT) to establish methodologies for the characterization of the associated diseases. For this purpose, immunochemical and molecular methods were used to identify the potyviruses present. The symptomatology of Dioscorea spp. at INIVIT’s germplasm collection was described. In addition, the severity and incidence in the germplasm collection and production areas were evaluated. As a result, the first report of yam mosaic virus (Potyvirus yamtesselati) and yam mild mosaic virus (Potyvirus yamplacidum) in Cuba is presented. The existence of resistant, tolerant, and susceptible cultivars to potyvirus-associated diseases in the germplasm collection was detected, and the incidence of these diseases was higher than 64% in the production areas evaluated. This study represents a step forward in the establishment of certification programs for propagating material of Dioscorea spp. in Cuba.

Impatiens walleriana was introduced into Brazil and is now widely cultivated as an ornamental plant. Impatiens plants from a public garden showing leaf mosaic and colour break symptoms were submitted to total RNA extraction and high throughput sequencing. Identity of 99% with Amaranthus leaf mottle virus (AmLMV, Potyvirus) was observed. This is the first report of AmLMV in both Impatiens walleriana and the Americas. [ABSTRACT FROM AUTHOR]

Viruses rely completely on host translational machinery to produce the proteins encoded by their genes. Controlling translation initiation is important for gaining translational advantage in conflicts between the host and virus. The eukaryotic translation initiation factor 4E (eIF4E) has been reported to be hijacked by potyviruses for virus multiplication. The role of translation regulation in defence and anti‐defence between plants and viruses is not well understood. We report that the transcript level of eIF6 was markedly increased in turnip mosaic virus (TuMV)‐infected Nicotiana benthamiana. TuMV infection was impaired by overexpression of N. benthamiana eIF6 (NbeIF6) either transiently expressed in leaves or stably expressed in transgenic plants. Polysome profile assays showed that overexpression of NbeIF6 caused the accumulation of 40S and 60S ribosomal subunits, the reduction of polysomes, and also compromised TuMV UTR‐mediated translation, indicating a defence role for upregulated NbeIF6 during TuMV infection. However, the polysome profile in TuMV‐infected leaves was not identical to that in leaves overexpressing NbeIF6. Further analysis showed that TuMV NIb protein, the RNA‐dependent RNA polymerase, interacted with NbeIF6 and interfered with its effect on the ribosomal subunits, suggesting that NIb might have a counterdefence role. The results propose a possible regulatory mechanism at the translation level during plant–virus interaction. [ABSTRACT FROM AUTHOR]

Background: In cellular organisms, inosine triphosphate pyrophosphatases (ITPases) prevent the incorporation of mutagenic deaminated purines into nucleic acids. These enzymes have also been detected in the genomes of several plant RNA viruses infecting two euphorbia species. In particular, two ipomoviruses produce replicase-associated ITPases to cope with high concentration of non-canonical nucleotides found in cassava tissues. Method: Using high-throughput RNA sequencing on the wild euphorbia species Mercurialis perennis, two new members of the families Potyviridae and Secoviridae were identified. Both viruses encode for a putative ITPase, and were found in mixed infection with a new partitivirid. Following biological and genomic characterization of these viruses, the origin and function of the phytoviral ITPases were investigated. Results: While the potyvirid was shown to be pathogenic, the secovirid and partitivirid could not be transmitted. The secovirid was found belonging to a proposed new Comovirinae genus tentatively named "Mercomovirus", which also accommodates other viruses identified through transcriptome mining, and for which an asymptomatic pollen-associated lifestyle is suspected. Homology and phylogenetic analyses inferred that the ITPases encoded by the potyvirid and secovirid were likely acquired through independent horizontal gene transfer events, forming lineages distinct from the enzymes found in cassava ipomoviruses. Possible origins from cellular organisms are discussed for these proteins. In parallel, the endogenous ITPase of M. perennis was predicted to encode for a C-terminal nuclear localization signal, which appears to be conserved among the ITPases of euphorbias but absent in other plant families. This subcellular localization is in line with the idea that nucleic acids remain protected in the nucleus, while deaminated nucleotides accumulate in the cytoplasm where they act as antiviral molecules. Conclusion: Three new RNA viruses infecting M. perennis are described, two of which encoding for ITPases. These enzymes have distinct origins, and are likely required by viruses to circumvent high level of cytoplasmic non-canonical nucleotides. This putative plant defense mechanism has emerged early in the evolution of euphorbias, and seems to specifically target certain groups of RNA viruses infecting perennial hosts. [ABSTRACT FROM AUTHOR]

Eukaryotic translation initiation factor 4E (eIF4E), which plays a pivotal role in initiating translation in eukaryotic organisms, is often hijacked by the viral genome‐linked protein to facilitate the infection of potyviruses. In this study, we found that the naturally occurring amino acid substitution D71G in eIF4E is widely present in potyvirus‐resistant watermelon accessions and disrupts the interaction between watermelon eIF4E and viral genome‐linked protein of papaya ringspot virus‐watermelon strain, zucchini yellow mosaic virus or watermelon mosaic virus. Multiple sequence alignment and protein modelling showed that the amino acid residue D71 located in the cap‐binding pocket of eIF4E is strictly conserved in many plant species. The mutation D71G in watermelon eIF4E conferred resistance against papaya ringspot virus‐watermelon strain and zucchini yellow mosaic virus, and the equivalent mutation D55G in tobacco eIF4E conferred resistance to potato virus Y. Therefore, our finding provides a potential precise target for breeding plants resistant to multiple potyviruses. [ABSTRACT FROM AUTHOR]

Pepper (Capsicum spp.) is an important solanaceous cash crop in Benin; however, productivity is limited due to several key constraints, especially diseases caused by viruses. We sought to understand farmers' perceptions of viral diseases, management strategies deployed, and to identify the virus population affecting pepper production in Benin. To assess farmers' perceptions and management of viral diseases, a survey was carried out in four agroecological zones of Benin. A total of 144 pepper farmers were interviewed using the snowball method. A total of 52 pepper leaf samples with virus-like symptoms were collected and diagnosed by reverse-transcriptase polymerase chain reaction (RT-PCR) or PCR. Pepper production systems varied across agroecological zones (P # 0.001) with a predominance of farms practicing monoculture (82%). The majority of farmers (89%) indicated that pests and diseases were the main constraints to increased production. Cucumber mosaic virus (92% of the total samples), Pepper vein yellow virus (52%), and Pepper veinal mottle virus (50%) were the major viruses detected in pepper fields in Benin. There were both single (29%) and mixed (71%) infections of the viruses, suggesting that mixed infections are common for pepper in Benin, confounding efforts to reduce virus infections. Nearly 100% of the farmers surveyed were not aware of these viral diseases. They also could not directly relate symptoms of virus infection to the presence of aphids, whiteflies, or thrips. Farmers relied primarily on synthetic insecticides (93%) to control virus vectors. Interestingly, some farmers applied commercial (12%) and homemade (17%) biopesticides, with neem-based preparations being the most widely used. A total of 15% of farmers used companion cropping with maize, mint or basil and 43% of farmers used crop rotation as a cultural management practice to control viral disease and vector pressure in pepper fields. The implications of this work include the importance of training farmers and extension agents on diagnosis of viruses and their vectors causing viral diseases. This study provides baseline information for the development of host-resistant cultivars and deployment of integrated pest management strategies for pepper in Benin to reduce farmer losses. [ABSTRACT FROM AUTHOR]

Symptoms such as severe mosaic, yellowing and necrosis of leaves have been observed in iris (Iris spp.) plants for many years. In this study, the presence of potyvirus species that can cause similar symptoms in iris plants was investigated. Field surveys were carried out in the province of Bilecik in the South Marmara region-Türkiye in the year 2022. In the study, a total of 41 iris plants were collected, including 34 symptomatic and 7 asymptomatic ones. Potyvirus infections were detected by conventional molecular methods using degenerate primers for amplification of the partial NIb (nuclear inclusion protein b) gene region specific to the genus Potyvirus. As a result of the molecular assays, potyvirus infection was detected in 6 plants showing symptoms caused by viruses. After nucleotide sequencing of the 6 Potyvirus fragments obtained, the infections were determined to be caused by iris severe mosaic virus (ISMV). These isolates showed over 94% nucleotide similarity among themselves and 82-99% similarity with the global isolate. Phylogenetic analyses showed that Potyvirus species were successfully separated among themselves according to the NIb gene region obtained with these degenerate primers. [ABSTRACT FROM AUTHOR]

Bean common mosaic virus (BCMV) was detected on common bean (Phaseolus vulgaris) plants showing wrinkled and/or narrow leaves, curling, shrinking and chlorosis of leaves, dwarfing of plants, and mottled pods in Inner Mongolia and named BCMV-22Huhe. Its genome has a size of 10,062 bp and was deposited in GenBank under the accession number OR778613. It is closely related to BCMV-Az (GenBank accession no. KP903372, in China) in the lineage of AzBMV. A recombination event was detected for BCMV-22Huhe among the 99 BCMV isolates published in the NCBI GenBank database, showing that BCMV-CJ25 (MK069986, found in Mexico) was a potential major parent, and the minor parent is unknown. This work is the first description of the occurrence of BCMV in Inner Mongolia, China. [ABSTRACT FROM AUTHOR]

Global food production is challenged by plant pathogens that cause significant crop losses. Fungi, bacteria, and viruses have long threatened sustainable and profitable agriculture. The danger is even higher in vegetatively propagated horticultural crops, such as garlic. Currently, quarantine, rouging infected plants, and control of natural vectors are used as the main means of disease and pest control in garlic crops. Agricultural biotechnology, meristem-tip culture, and cryotherapy offer solutions for virus eradication and for the multiplication of 'clean stocks', but at the same time, impact the symbiotic and beneficial components of the garlic microbiome. Our research involves the first metatranscriptomic analysis of the microbiome of garlic bulb tissue, PCR analyses, and a biological assay of endophytes and pathogens. We have demonstrated that in vitro sanitation methods, such as shoot tip culture or cryotherapy can alter the garlic microbiome. Shoot tip culture proved ineffective in virus elimination, but reduced bacterial load and eliminated fungal infections. Conversely, cryotherapy was efficient in virus eradication but demolished other components of the garlic microbiome. Garlic plants sanitized by cryotherapy exhibited a lower survival rate, and a longer in vitro regeneration period. The question arises whether total eradication of viruses, at the expense of other microflora, is necessary, or if a partial reduction in the pathogenic load would suffice for sanitized garlic production. We explore this question from both scientific and commercial perspectives. [ABSTRACT FROM AUTHOR]

The genus Potyvirus is considered as the largest among plant single‐stranded (positive‐sense) RNA viruses, causing considerable economic damage to vegetable and fruit crops worldwide. Through the coordinated action of four viral proteins and a few identified host factors, potyviruses exploit the endomembrane system of infected cells for their replication and for their intra‐ and intercellular movement to and through plasmodesmata (PDs). Although a significant amount of data concerning potyvirus movement has been published, no synthetic review compiling and integrating all information relevant to our current understanding of potyvirus transport is available. In this review, we highlight the complexity of potyvirus movement pathways and present three potential nonexclusive mechanisms based on (1) the use of the host endomembrane system to produce membranous replication vesicles that are targeted to PDs and move from cell to cell, (2) the movement of extracellular viral vesicles in the apoplasm, and (3) the transport of virion particles or ribonucleoprotein complexes through PDs. We also present and discuss experimental data supporting these different models as well as the aspects that still remain mostly speculative. [ABSTRACT FROM AUTHOR]

The garlic (Allium sativum L.) cultivated in the O'Higgins Region, the main garlic-producing area in Chile, is the commercial type known as pink garlic, which presents a low yield and a high prevalence of symptoms associated with viral infections. A survey was carried out in the three localities of the region that cultivate this vegetable to identify, by reverse transcription polymerase chain reaction (RT-PCR), the presence of Onion yellow dwarf virus (OYDV) and Leek yellow stripe virus (LYSV). The results indicated a prevalence of 99.5% and 54.0% respectively. In addition, a molecular and phylogenetic analysis of the amplified genome fragments for both viruses was performed. Using the nucleotide BLAST (BLASTn) tool, nucleotide sequences were compared with sequences available in the National Center for Biotechnology Information (NCBI) database. The Chilean sequences were aligned with complete sequences available at NCBI and a phylogenetic tree was constructed using the Neighbor-Joining method. The results showed genetic variability among Chilean isolates. [ABSTRACT FROM AUTHOR]

Celery mosaic virus (CeMV), member of genus Potyvirus, is reported for the first time in Indonesia, from celery plants (Apium graveolens) in a vegetable field at Berastagi, North Sumatera Province. The plants possessed mosaic and vein clearing symptoms on the leaves as typical of CeMV infection. Virus incidence was confirmed by RT-PCR using degenerate potyvirus primer which amplified partial coat protein and 3’-UTR of the viral genome. Phylogenetic tree analysis placed Indonesian CeMV isolates in one separated clade within CeMV group and shared 96.5%–96.7% nucleotide identity with exemplar isolate of CeMV.

Kitosan dan ekstrak kasar daun bugenvil diketahui mampu mengendalikan beberapa virus tanaman termasuk Bean common mosaic virus strain Blackeye Cowpea (BCMV-BlC). Untuk mengurangi penggunaan bahan baku dan peningkatan keefektifan juga stabilitasnya, kedua bahan perlu disintesis menggunakan teknologi nanpopartikel (NP). Penelitian bertujuan menyintesis nanopartikel kitosan, ekstrak daun bugenvil, dan kombinasinya menggunakan modifikasi metode gelasi ionik, mengarakterisasi NP dan mengevaluasi potensi NP untuk mengendalikan BCMV-BlC pada tanaman indikator Chenopodium amaranticolor. Nanopartikel kitosan (Kit-NP), ekstrak daun bugenvil (EDB-NP), dan kombinasinya (KEDB-NP) berhasil disintesis dengan rata-rata ukuran partikel berturut-turut sebesar 99.72, 163.68, dan 221.42 nm berdasarkan pengamatan di bawah transmission electron microscope (TEM) dan berbentuk bola (sferis) berdasarkan hasil analisis scanning electron microscope (SEM). Hasil analisis fourier transform infrared (FTIR), KEDB-NP menunjukkan gugus fungsi berturut-turut hidroksil, alkena, amina, cincin aromatik, dan senyawa alifatik organohalogen. Daun C. amaranticolor yang diberi perlakuan Kit-NP, EDB-NP, KEDB-NP dan juga non-NP pada konsentrasi 100-800 ppm sebelum inokulasi virus menunjukkan jumlah rata-rata lesio lokal nekrotik (LLN) nyata lebih rendah dibandingkan kontrol tanaman sakit tanpa perlakuan dan tidak berbeda nyata antarkonsentrasi. Perlakuan NP dan non-NP sebelum inokulasi virus secara nyata memperpanjang periode inkubasi dan menekan pembentukan LLN dengan keefektifan 67.5%–100% dibandingkan dengan aplikasi setelah inokulasi virus. Di antara konsentrasi yang diuji, konsentrasi NP antara 100 dan 300 ppm yang diaplikasikan sebelum penularan virus menunjukkan paling efektif dalam menghambat pembentukan LLN. Sintesis EDB-NP, Kit-NP, dan KEDB-NP menggunakan sangat sedikit bahan baku, namun keefektifannya sebanding dengan bentuk non-NPnya dalam mengendalikan infeksi BCMV.

Yam (Dioscorea spp.) is a staple food crop with cultural, nutritional and economic significance for millions of small-scale farmers in sub-Saharan Africa. While various virus-like symptoms such as mosaic and chlorosis are frequently observed in yam fields in Ethiopia, little information is available on the prevalence, distribution, and molecular characteristics of viruses causing these symptoms. The aim of this study was to investigate the incidence and distribution of yam viruses and determine the primary cause of yam mosaic diseases (YMD) in Ethiopia. Both symptomatic (n = 280) and asymptomatic (n = 110) yam leaf samples were collected and tested for potyviruses using ACP‐ELISA. In addition, the symptomatic leaf samples were screened for yam mosaic virus (YMV), yam mild mosaic virus (YMMV), and cucumber mosaic virus (CMV) by DAS-ELISA. Subsequently, total RNA was extracted from 130 leaf samples comprising 94 symptomatic and 36 asymptomatic samples representing the different study areas. The representative RT-PCR amplicons (n = 6) were Sanger sequenced. The ACP-ELISA and DAS-ELISA results showed 9.2%, and 12.9% YMV infection, respectively, while the RT-PCR analysis showed 28.5% YMV positivity rate. Both CMV and YMMV were not detected in any of the samples tested. Thus, YMV is confirmed as the primary cause of YMD in Ethiopia. YMV isolates from Ethiopia shared 92–93% nucleotide identity among themselves and 85–99% with other YMV isolates from the GenBank. Phylogenetic analysis revealed that YMV isolates from Ethiopia, South America, and west-central Africa have the most recent common ancestor, while isolates from China and Japan are clustered as sister groups. This study enhances our understanding of YMV's genetic diversity and provides valuable information regarding the first report of YMV in Ethiopia.

The potential antagonistic effect of babaco mosaic virus (BabMV) against papaya ringspot virus (PRSV) was investigated under greenhouse and field conditions. Carica papaya plants previously inoculated with BabMV were challenged with PRSV and monitored over time. Reverse-transcription quantitative PCR showed an average 61% reduction of PRSV genomic RNA in BabMV-PRSV-infected plants compared with singly infected plants. However, there was no antagonistic effect in the phenotypic response to PRSV, as leaf symptoms associated with PRSV were not different in mixed infections of BabMV-PRSV compared with PRSV singly infected plants. Similar results were observed in the field, where PRSV was detected in 47.1% of plants previously inoculated with BabMV and showed severe leaf symptoms. Our findings show that BabMV does not act as an antagonist against PRSV in C. papaya. [Figure: see text] Copyright © 2023 The Author(s). This is an open access article distributed under the CC BY-NC-ND 4.0 International license.

Nine viruses of the bean common mosaic virus subgroup of potyviruses are major international crop pathogens, but their phylogenetically closest relatives from non-crop plants have mostly been found only in SE Asia and Oceania, which is thus likely to be their “centre of emergence”. We have compared over 700 of the complete genomic ORFs of the crop pandemic and the non-crop viruses in various ways. Only one-third of crop virus genomes are non-recombinant, but more than half the non-crop virus genomes are. Four of the viruses were from crops domesticated in the Old World (Africa to SE Asia), and the other five were from New World crops. There was a temporal signal in only three of the crop virus datasets, but it confirmed that the most recent common ancestors of all the crop viruses were before inter-continental marine trade started after 1492 CE, whereas all the crown clusters of the phylogenies are from after that date. The non-crop virus datasets are genetically more diverse than those of the crop viruses, and Tajima’s D analyses showed that their populations were contracting, and only one of the crop viruses had a significantly expanding population. dN/dS analyses showed that most of the genes and codons in all the viruses were under significant negative selection, and the few that were under significant positive selection were mostly in the PIPO-encoding region of the P3 protein, or the PIPO protein itself. Interestingly, more positively selected codons were found in non-crop than in crop viruses, and, as the hosts of the former were taxonomically more diverse than the latter, this may indicate that the positively selected codons are involved in host range determination; AlphaFold3 modelling was used to investigate this possibility.

East Asian Passiflora virus (EAPV) causes passionfruit woodiness disease, a major threat limiting passionfruit production in eastern Asia, including Taiwan and Vietnam. In this study, an infectious cDNA clone of a Taiwanese severe isolate EAPV-TW was tagged with a green fluorescent protein (GFP) reporter to monitor the virus in plants. Nicotiana benthamiana and yellow passionfruit plants inoculated with the construct showed typical symptoms of EAPV-TW. Based on our previous studies on pathogenicity determinants of potyviral HC-Pros, a deletion of six amino acids (d6) alone and its association with a point mutation (F8I, simplified as I8) were conducted in the N-terminal region of the HC-Pro gene of EAPV-TW to generate mutants of EAPV-d6 and EAPV-d6I8, respectively. The mutant EAPV-d6I8 caused infection without conspicuous symptoms in N. benthamiana and yellow passionfruit plants, while EAPV-d6 still induced slight leaf mottling. EAPV-d6I8 was stable after six passages under greenhouse conditions and displayed a zigzag pattern of virus accumulation, typical of a beneficial protective virus. The cross-protection effectiveness of EAPV-d6I8 was evaluated in both N. benthamiana and yellow passionfruit plants under greenhouse conditions. EAPV-d6I8 conferred complete cross-protection (100%) against the wild-type EAPV-TW-GFP in both N. benthamiana and yellow passionfruit plants, as verified by no severe symptoms, no fluorescent signals, and PCR-negative status for GFP. Furthermore, EAPV-d6I8 also provided complete protection against Vietnam’s severe strain EAPV-GL1 in yellow passionfruit plants. Our results indicate that the attenuated mutant EAPV-d6I8 has great potential to control EAPV in Taiwan and Vietnam via cross-protection.

Plant viruses cause severe losses in agricultural production. Parasite-derived resistance (PDR) offers a promising avenue for developing disease-resistant varieties independent of resistance genes. However, for potyviruses with great agricultural importance, such as soybean mosaic virus (SMV), systematic research on viral genes that can be used for PDR has not been conducted. In this study, we transiently expressed the untranslated region (UTR) or each protein-coding cistron of SMV in Nicotiana benthamiana to evaluate their potential role in conferring PDR. A viral suppressor of RNA silencing (VSR) was also applied to investigate the possible mechanisms of the PDR. The results showed that the transient overexpression of UTR and each cistron of SMV could inhibit SMV infection. The expression of VSR in N. benthamiana leaves could compromise UTR and most of the SMV cistron-mediated inhibition of SMV infection, indicating the involvement of RNA silencing in PDR. In comparison, the expression of VSR could not compromise the PDR conferred by coat protein (CP), P3N-PIPO, cylindrical inclusion (CI), and NIa-Pro, suggesting that these viral cistrons may play roles in PDR at the protein level. These results reveal diverse mechanisms in PDR conferred by different viral cistrons and provide potential gene candidates that can be used for transgenic approaches against SMV.

Spodoptera frugiperda (fall armyworm) is a notorious pest that threatens maize production worldwide. Current control measures involve the use of chemical insecticides and transgenic maize expressing Bacillus thuringiensis (Bt) toxins. Although additional transgenes have confirmed insecticidal activity, limited research has been conducted in maize, at least partially due to the technical difficulty of maize transformation. Here, we describe implementation of a sugarcane mosaic virus (SCMV) vector for rapidly testing the efficacy of both endogenous maize genes and heterologous genes from other organisms for the control of S. frugiperda in maize. Four categories of proteins were tested using the SCMV vector: (i) maize defence signalling proteins: peptide elicitors (Pep1 and Pep3) and jasmonate acid conjugating enzymes (JAR1a and JAR1b); (ii) maize defensive proteins: the previously identified ribosome-inactivating protein (RIP2) and maize proteinase inhibitor (MPI), and two proteins with predicted but unconfirmed anti-insect activities, an antimicrobial peptide (AMP) and a lectin (JAC1); (iii) lectins from other plant species: Allium cepa agglutinin (ACA) and Galanthus nivalis agglutinin (GNA); and (iv) scorpion and spider toxins: peptides from Urodacus yaschenkoi (UyCT3 and UyCT5) and Hadronyche versuta (Hvt). In most cases, S. frugiperda larval growth was reduced by transient SCMV-mediated overexpression of genes encoding these proteins. Additionally, experiments with a subset of the SCMV-expressed genes showed effectiveness against two aphid species, Rhopalosiphum maidis (corn leaf aphid) and Myzus persicae (green peach aphid). Together, these results demonstrate that SCMV vectors are a rapid screening method for testing the efficacy and insecticidal activity of candidate genes in maize.

A headspace solid-phase microextraction-gas chromatography-mass spectrometry (HS-SPME/GC-MS) method was used to study the volatile organic compounds (VOCs) associated with the differential immune response of tomato plants infected with the recombinant strain of potato virus Y (PVYC-to), necrogenic to tomato. Analysis was carried out in UC82 (UC), a virus susceptible tomato variety, comparing the same UC plants grafted or not onto a virus tolerant tomato ecotype, Manduria (Ma); the three types of samples used for the GC-MS analysis were mock-inoculated UC/Ma plants, UC/Ma+PVYC-to and UC+PVYC-to plants; the VOCs obtained were 111. Results from symptomatic PVYC-to-infected UC plants showed a VOCs composition enriched in alcohols, fatty acid derivates, benzenoids, and salicylic acid derivatives, while in mock-inoculated UC/Ma plants VOCs were mainly characterized by methyl ester compounds. The VOC profile was in line with RNAseq data analyses, denoting that PVYC-to viral RNA accumulation and disease symptoms induce the specific transcriptional activation of genes involved in VOCs biosynthesis. Furthermore, principal component analysis highlighted that VOCs of PVYC-to-infected and mock-inoculated grafted plants were much closer each other than that of symptomatic PVYC-to-infected non-grafted UC plants. These results suggest that VOCs profiles of tomato plants are related to the viral RNA accumulation, disease intensity and graft-derived tolerance to PVYC-to infection.

Plant viruses account for enormous agricultural losses worldwide, and the most effective way to combat them is to identify genetic material conferring plant resistance to these pathogens. Aiming to identify genetic associations with responses to infection, we screened a large panel of Arabidopsis thaliana natural inbred lines for four disease-related traits caused by infection by A. thaliana-naïve and -adapted isolates of the natural pathogen turnip mosaic virus (TuMV). We detected a strong, replicable association in a 1.5 Mb region on chromosome 2 with a 10-fold increase in relative risk of systemic necrosis. The region contains several plausible causal genes as well as abundant structural variation, including an insertion of a Copia transposon into a Toll/interleukin receptor (TIR-NBS-LRR) coding for a gene involved in defense, that could be either a driver or a consequence of the disease-resistance locus. When inoculated with TuMV, loss-of-function mutant plants of this gene exhibited different symptoms than wild-type plants. The direction and severity of symptom differences depended on the adaptation history of the virus. This increase in symptom severity was specific for infections with the adapted isolate. Necrosis-associated alleles are found worldwide, and their distribution is consistent with a trade-off between resistance during viral outbreaks and a cost of resistance otherwise, leading to negative frequency-dependent selection.