Leaf Curl Virus Infection Research Articles

A simplified single-leaflet graft inoculation method and a Duplex PCR assay for the identification of the Tomato Yellow Leaf Curl Virus infection in tomatoes

Tomato yellow leaf curl virus (TYLCV), a member of the Geminivirus genus, has caused an epidemic disease in tomato worldwide, including in Azerbaijan. TYLCV is a phloem-limited virus that is transmitted in a semi-persistent manner by whiteflies (Bemisia tabaci). Experimental propagation of TYCV has been performed primarily by using the single-leaflet grafting inoculation method. To develop a simple and effective method for transmission of TYLCV, we investigated grafting single-leaflets from tomato plants infected with TYLCV to recipient tomato seedlings. Fifty-one (51) tomato seedlings were tested and forty-eight (48) were grafted successfully with single-leaflets infected with TYLCV. Among them, forty-six (46) seedlings (92%) were systemically infected with TYLCV and developed typical symptoms. In our study, we found that single-leaflet grafting could provide a sufficient amount of inoculum for the transmission of TYLCV to the grafted tomato seedlings. The reported results regarding the development of the TYLCV inoculation and monitoring method and its application to study host plant-virus interaction showed that it could be used as an efficient alternative inoculation method.

Variability in indigenous Pakistani tomato lines and worldwide reference collection for Tomato Mosaic Virus (ToMV) and Tomato Yellow Leaf Curl Virus (TYLCV) infection.

Local and exotic germplasm of tomato remains a major source for genetic improvement. Assessment of such lines for biotic stresses particularly viral diseases are the most important criteria for selection in Pakistan, where Tomato Yellow Leaf Curl Virus (TYLCV) and Tomato Mosaic Virus (ToMV) are the major diseases/viruses. A set of 40 accessions (including indigenous Pakistani lines and exotic germplasm from Europe, the United States, and Asia) were evaluated for their resistance/infection response to ToMV with artificial inoculation under greenhouse conditions. Infection response was quantified through disease scoring and DAS-ELISA test (for ToMV). A subset of 24 lines, was further screened for TYLCV using disease scoring and TAS-ELISA. The tested lines showed significant variability for resistance to ToMV. Only one accession (Acc-17878) was resistant to the ToMV whereas seven accessions i.e. Acc-17890, AVR-261, CLN-312, AVR-321, EUR-333, CLN-352, and CLN-362 expressed resistance to TYLCV. Correlation between phenotypic evaluation was confirmed by the ELISA results in both diseases, although both tools complemented to assess the viral infection status. In future, tomato breeding programs must consider breeding for ToMV and TYLCV resistance (using identified germplasm in our study) so as to deliver virus resistant tomato varieties.

Transcriptional and epigenetic changes during tomato yellow leaf curl virus infection in tomato

BackgroundGeminiviruses are DNA plant viruses that cause highly damaging diseases affecting crops worldwide. During the infection, geminiviruses hijack cellular processes, suppress plant defenses, and cause a massive reprogramming of the infected cells leading to major changes in the whole plant homeostasis. The advances in sequencing technologies allow the simultaneous analysis of multiple aspects of viral infection at a large scale, generating new insights into the molecular mechanisms underlying plant-virus interactions. However, an integrative study of the changes in the host transcriptome, small RNA profile and methylome during a geminivirus infection has not been performed yet. Using a time-scale approach, we aim to decipher the gene regulation in tomato in response to the infection with the geminivirus, tomato yellow leaf curl virus (TYLCV).ResultsWe showed that tomato undergoes substantial transcriptional and post-transcriptional changes upon TYLCV infection and identified the main altered regulatory pathways. Interestingly, although the principal plant defense-related processes, gene silencing and the immune response were induced, this cannot prevent the establishment of the infection. Moreover, we identified extra- and intracellular immune receptors as targets for the deregulated microRNAs (miRNAs) and established a network for those that also produced phased secondary small interfering RNAs (phasiRNAs). On the other hand, there were no significant genome-wide changes in tomato methylome at 14 days post infection, the time point at which the symptoms were general, and the amount of viral DNA had reached its maximum level, but we were able to identify differentially methylated regions that could be involved in the transcriptional regulation of some of the differentially expressed genes.ConclusionWe have conducted a comprehensive and reliable study on the changes at transcriptional, post-transcriptional and epigenetic levels in tomato throughout TYLCV infection. The generated genomic information is substantial for understanding the genetic, molecular and physiological changes caused by TYLCV infection in tomato.

Effect of Tomato yellow leaf curl virus (TYLCV) Infection of some Tomato (Solanum lycopersicom L.) Genotypes on Fruits Content of Lycopene and some Vitamins

The response of some genotypes of tomato plant (Solanum lycopersicom L.) to infection with the Tomato yellow leaf curl virus (TYLCV) was tested, and the effect of infection on genotypes (123, Narcan and Summer 21) on the fruit content of vitamins C and E and lycopene was evaluated. The field experiment was carried out in the western orchards of Samawah, Al-Muthanna Governorate, Iraq, and the analysis of vitamins and lycopene was carried out in the laboratories of Ghayat Al-Maarifa Company - Babylon. The genotypes were inoculated with whitefly (Bemisia tabaci) and tested by polymerase chain reaction (PCR). The results showed that all genotypes of tomato plants were sensitive to the virus, with differences in the time of appearance and severity of disease symptoms. The genotypes Nahrayn and Summer 21 were the most severely infected with the virus (96 and 87%, respectively) compared to the rest of the genotypes. The results showed a decrease in the vitamin C and vitamin E content of tomato fruits to 8.84 and 0.403 mg /100 gm, respectively, in virus-infected plants, with a significant difference from their normal levels in uninoculated plants, which resulted in 15.8 and 0.931 mg /100 gm, respectively. It was also observed that infection with the virus had a clear effect and significantly decreased the level of lycopene to 9.79 mg/kg fresh weight compared to 14.12 mg/kg fresh weight in uninfected plants. Regardless of the type of plant, infection with the Tomato yellow leaf curl virus (TYLCV) significantly reduced the average dry weight of shoots and roots of infected plants by 28.89 and 3.15 g/plant, compared to 84.08 and 10.13 g/plant for control plants, respectively. The results also showed a clear effect of the virus in reducing the yield of genotypes, which recorded 409.1 g/plant, with a significant difference from the yield of the same genotypes not infected with the virus, which recorded 1697.3 g/plant.

The antiviral potential of macroalgae in suppressing Sweet potato leaf curl virus (SPLCV) infection in sweet potatoes

Abstract. Listihani L, Yuniti IGAD, Sapanca PLY, Pandawani NP, Selangga DGW. 2023. The antiviral potential of macroalgae in suppressing Sweet potato leaf curl virus (SPLCV) infection in sweet potatoes. Biodiversitas 24: 4079-4086. Sweet potato leaf curl virus (SPLCV) was first found in sweet potatoes in Indonesia in 2022. Prevention of spread of virus is essential, especially by using macroalgae extract which is environmentally friendly and has antiviral activity. The aim of present research was to test the potential of sea macroalgae to suppress SPLCV infection and to analyze phytochemicals of potential macroalgae containing an antiviral substance. Macroalgae extract was sprayed on the test plants that were infected by SPLCV. The observed parameters were changes in symptoms, disease incidence and severity, virus confirmation by PCR, and phytochemical analysis. The test results up to day 21 showed that Eucheuma spinosum was found to be effective in suppressing SPLCV infection in sweet potatoes, up to symptomless infection in young leaves. E. spinosum and E. cottonii suppressed disease incidence by 80% and 40% and lower disease severity as much as 71% and 48%, while E. serra showed less ability to suppress SPLCV infection. The two macroalgae had flavonoid, saponin, and steroid content which may be the reason to suppress the viral infection. The results of PCR analysis showed that microalgal extract had the highest nucleotide and amino acid homology with Gianyar (LC586170) isolate with values of 99.7 and 100%. The macroalgae with the highest ability to suppress the virus were E. spinosum and E. cottonii. This showed that the application of macroalgae extract did not change the amino acid sequence of SPLCV isolate.

WRKY1 represses the WHIRLY1 transcription factor to positively regulate plant defense against geminivirus infection.

Geminiviruses constitute the largest group of known plant viruses and cause devastating diseases and economic losses in many crops worldwide. Due to limited naturally occurring resistance genes, understanding plant antiviral defense against geminiviruses is critical for finding host factors of geminiviruses and development of strategies for geminivirus control. Here we identified NbWRKY1 as a positive regulator of plant defense against geminivirus infection. Using tomato yellow leaf curl China virus/tomato yellow leaf curl China betasatellite (TYLCCNV/TYLCCNB) as a representative geminivirus, we found that NbWRKY1 was upregulated in response to TYLCCNV/TYLCCNB infection. Overexpression of NbWRKY1 attenuated TYLCCNV/TYLCCNB infection, whereas knockdown of NbWRKY1 enhanced plant susceptibility to TYLCCNV/TYLCCNB. We further revealed that NbWRKY1 bound to the promoter of the NbWHIRLY1 (NbWhy1) transcription factor and inhibited the transcription of NbWhy1. Consistently, NbWhy1 negatively regulates plant response against TYLCCNV/TYLCCNB. Overexpression of NbWhy1 significantly accelerated TYLCCNV/TYLCCNB infection. Conversely, knockdown of NbWhy1 led to impaired geminivirus infection. Furthermore, we demonstrated that NbWhy1 interfered with the antiviral RNAi defense and disrupted the interaction between calmodulin 3 and calmodulin-binding transcription activator-3. Moreover, the NbWRKY1-NbWhy1 also confers plant antiviral response toward tomato yellow leaf curl virus infection. Taken together, our findings suggest that NbWRKY1 positively regulates plant defense to geminivirus infection by repressing NbWhy1. We propose that the NbWRKY1-NbWhy1 cascade could be further employed to control geminiviruses.

The The Effect of Gamma Rays on Local Chilli Infected to Pepper Yellow Leaf Curl Virus Infection (Begomovirus)

Cabai merupakan salah satu komoditas hortikultura bernilai ekonomi tinggi di Indonesia. Cabai lokal Karo berbatang ungu merupakan cabai yang memiliki keunggulan produksi dan pertumbuhan vegetatif tinggi, namun sangat rentan terhadap penyakit virus keriting kuning oleh begomovirus. Salah satu upaya pengendalian begomovirus ialah dengan perakitan genotipe baru yang tahan melalui induksi iradiasi sinar gamma. Penelitian bertujuan mengkaji pengaruh iradiasi sinar gamma pada benih cabai lokal Karo berbatang ungu terinfeksi begomovirus untuk mendapatkan calon genotipe mutan yang tahan. Benih dari tanaman cabai terinfeksi begomovirus diberi perlakuan iradiasi sinar gamma dengan taraf dosis 150, 200, dan 250 Gy untuk mendapatkan tanaman mutan 1 (M1). Benih sehat dan benih berasal dari tanaman sakit tanpa perlakuan digunakan sebagai tanaman kontrol. Parameter yang diamati meliputi insidensi dan keparahan penyakit, AUDPC dan deteksi begomovirus pada tanaman M1 dan benih generasi kedua (M2). Perlakuan iradiasi sinar gamma taraf dosis 150 Gy pada benih cabai terinfeksi begomovirus menunjukkan rata-rata insidensi, keparahan penyakit, dan AUDPC paling rendah dibandingkan dengan perlakuan lainnya pada tanaman mutan M1 dan M2. Berdasarkan deteksi dengan PCR pada tanaman mutan M2, dari perlakuan dosis 150 Gy didapatkan 7 calon genotipe tahan begomovirus terbanyak di antara perlakuan lainnya.

Genome-wide identification and expression analysis of wall-associated kinase (WAK) and WAK-like kinase gene family in response to tomato yellow leaf curl virus infection in Nicotiana benthamiana

BackgroundTomato yellow leaf curl virus (TYLCV) is a major monopartite virus in the family Geminiviridae and has caused severe yield losses in tomato and tobacco planting areas worldwide. Wall-associated kinases (WAKs) and WAK-like kinases (WAKLs) are a subfamily of the receptor-like kinase family implicated in cell wall signaling and transmitting extracellular signals to the cytoplasm, thereby regulating plant growth and development and resistance to abiotic and biotic stresses. Recently, many studies on WAK/WAKL family genes have been performed in various plants under different stresses; however, identification and functional survey of the WAK/WAKL gene family of Nicotiana benthamiana have not yet been performed, even though its genome has been sequenced for several years. Therefore, in this study, we aimed to identify the WAK/WAKL gene family in N. benthamiana and explore their possible functions in response to TYLCV infection.ResultsThirty-eight putative WAK/WAKL genes were identified and named according to their locations in N. benthamiana. Phylogenetic analysis showed that NbWAK/WAKLs are clustered into five groups. The protein motifs and gene structure compositions of NbWAK/WAKLs appear to be highly conserved among the phylogenetic groups. Numerous cis-acting elements involved in phytohormone and/or stress responses were detected in the promoter regions of NbWAK/WAKLs. Moreover, gene expression analysis revealed that most of the NbWAK/WAKLs are expressed in at least one of the examined tissues, suggesting their possible roles in regulating the growth and development of plants. Virus-induced gene silencing and quantitative PCR analyses demonstrated that NbWAK/WAKLs are implicated in regulating the response of N. benthamiana to TYLCV, ten of which were dramatically upregulated in locally or systemically infected leaves of N. benthamiana following TYLCV infection.ConclusionsOur study lays an essential base for the further exploration of the potential functions of NbWAK/WAKLs in plant growth and development and response to viral infections in N. benthamiana.

The Streptomyces chromofuscus Strain RFS-23 Induces Systemic Resistance and Activates Plant Defense Responses against Tomato Yellow Leaf Curl Virus Infection

Insect-vectored plant viruses pose a serious threat to sustainable production of economically important crops worldwide. This demands a continuous search for environmentally-friendly, sustainable and efficient approaches based on biological agents to address the mounting challenges of viral disease management. To date, the efficacy of actinomycetes bacteria against DNA plant viruses remains unknown. Here, through comparative analyses, we demonstrate that the RFS-23 strain of Streptomyces cellulase possesses protective activity as it positively regulated the plant growth and development. and diminished the severity, of disease symptoms, together with reduced accumulation of Tomato yellow leaf curl virus (TYLCV) DNA. The RFS-23 strain maintained relative chlorophyll contents by promoting the expression of genes (CLH1, HEMA1 and PORA) associated with chlorophyll biogenesis. As compared to another strain, CTF-20, the RSF-23 induced a significantly higher expression of plant defense-related genes (NbCIS and NbNCED) associated with biogenesis and accumulation of salicylic acid and abscisic acid. Additionally, the activity of antioxidant enzymes (SOD, CAT, POD and MDA) was significantly enhanced by RSF-23 treatment, despite the presence of viral infection. These findings suggest that RSF-23 is a novel biocontrol agent with protective activity, and it could be a potential candidate for the management of plant viral infections.

Physiological and transcriptomic analyses revealed gene networks involved in heightened resistance against tomato yellow leaf curl virus infection in salicylic acid and jasmonic acid treated tomato plants.

Tomato yellow leaf curl virus (TYLCV), a member of the genus Begomovirus of the Geminiviridae family, causes leaf curl disease of tomato that significantly affects tomato production worldwide. SA (salicylic acid), JA (jasmonic acid) or the JA mimetic, COR (coronatine) applied exogenously resulted in improved tomato resistance against TYLCV infection. When compared to mock treated tomato leaves, pretreatment with the three compounds followed by TYCLV stem infiltration also caused a greater accumulation of H2O2. We employed RNA-Seq (RNA sequencing) to identify DEGs (differentially expressed genes) induced by SA, JA, COR pre-treatments after Agro-inoculation of TYLCV in tomato. To obtain functional information on these DEGs, we annotated genes using gene ontology (GO) and Kyoto encyclopedia of genes and genomes (KEGG) databases. Based on our comparative analysis, differentially expressed genes related to cell wall metabolism, hormone signaling and secondary metabolism pathways were analyzed in compound treated samples. We also found that TYLCV levels were affected in SlNPR1 and SlCOI1 silenced plants. Interestingly, compared to the mock treated samples, SA signaling was hyper-activated in SlCOI1 silenced plants which resulted in a significant reduction in viral titer, whereas in SINPR1 silencing tomato plants, there was a 19-fold increase in viral load. Our results indicated that SA, JA, and COR had multiple impacts on defense modulation at the early stage of TYLCV infection. These results will help us better understand SA and JA induced defenses against viral invasion and provide a theoretical basis for breeding viral resistance into commercial tomato accessions.

Efficacy of Three Antiviral Agents and Resistant Cultivars on Tomato Yellow Leaf Curl Virus in Tomato

Recently, several in vitro studies have reported antiviral activity of agents of systemic acquired resistance against plant virus infection, but the approach has not been applied in a wide range of agricultural fields. The objective of this study was to evaluate the inhibitory effect of the exogenous application of salicylic acid (SA), chitosan (CH), or eugenol (EG) in tomato yellow leaf curl virus (TYLCV) infection of greenhouse-grown tomato plants. In vitro, the initial time of symptom was observed in TYLCV-infected plants (VP) of the resistant cultivar ‘Superdotaerang’ at 12 days post inoculation (dpi) after application of antiviral agents. At 32 dpi, the disease rate of TYLCV in the CHT+VP (0.1% chitosan and virus infected control) treated plants was 87.5%, lower than that of the other treatment. However, the virus content in the CHT+VP treated plants was higher than those of the other treatments, and SA, EG, and CH did not show significant effect on plant height or shoot and root fresh weight. Our results from summer-cultivated greenhouse-grown tomatoes show that none of the tested agents had an inhibitory activity on viral infection or yield of tomato ‘Dotaerangsola’cultivar. In contrast, all treated ‘TY Giants’ cultivars that possessed TYLCV resistance genes Ty-1 and Ty-3a did not show typical symptoms and the virus content was remarkably lower than those in the TYLCV treated plants in ‘Superdotaerang’. The results of this research indicated that the planting of resistant tomato cultivars was effective method instead of using SA, EG, and CH (known as resistance-inducing factors for control) of TYLCV in the field.

Effect of Tomato Yellow Leaf Curl Virus Infection on Some Growth Indicators of Pepper Hybrids Grown Under Plastic House Conditions in Lattakia Governorate, Syria

Hamdan, R.S., I.D. Ismail and I. Akel. 2021. Effect of Tomato Yellow Leaf Curl Virus Infection on Some Growth Indicators of Pepper Hybrids Grown Under Plastic House Conditions in Lattakia Governorate, Syria. Arab Journal of Plant Protection, 39(4): 309-316. https://doi.org/10.22268/AJPP-39.4.309316 This study aimed to evaluate the effect of Tomato yellow leaf curl virus (TYLCV) infection on some growth parameters of several pepper hybrids grown under protected cultivation along the Syrian coast. Four pepper hybrids (Capsicum annum) were tested, two hot (Lahab, Sirad) and two sweet (Nevada, Dallas) peppers. The research was carried out during the 2020-2021 growing season in a plastic house at the Agriculture Scientific Research Center in Lattakia, using a randomized complete block design, with 8 treatments, three replicates and 5 plants per replicate. The results obtained showed that the sweet pepper hybrids (Nevada, Dallas) were more sensitive to infection with Tomato yellow leaf curl virus than the hot pepper hybrids (Lahab, Sirad), without significant differences among them. The pepper hybrid Nevada did not show any apparent symptoms, and the effect of the virus on some growth parameters (number flowers, flower setting, and the leaf surface area) was evident in comparison with other hybrids, but the differences were not significant. The Dallas, Sirad and Lahab pepper hybrids showed visible symptoms in response to infection with infection rate of 93.33%, 80% and 80%, respectively. The effect of virus infection on the growth parameters of these hybrids was variable. The reduction in the flowers number of Nevada, Dallas, Cirad and Lahab after 45 days of infection was 33%, 31.10%, 10.23% and 5.07%, respectively, and also with a reduction in the number of flowers setting of 77.39%, 20.87%, 23.33% and 66.68%, respectively. The same was true for the leaf surface area, where reduction rate for the Nevada, Dallas, Sirad and Lahab hybrids 30 days after infection was 48.17%, 53.06%, 16.45% and 36.6%, respectively. Keywords: Tomato yellow leaf curl virus, pepper hybrids, growth parameter, host resistance, protected agriculture.

Small RNA Profiling of Susceptible and Resistant Ty-1 Encoding Tomato Plants Upon Tomato Yellow Leaf Curl Virus Infection.

Ty-1 presents an atypical dominant resistance gene that codes for an RNA-dependent RNA polymerase (RDR) of the gamma class and confers resistance to tomato yellow leaf curl virus (TYLCV) and other geminiviruses. Tomato lines bearing Ty-1 not only produce relatively higher amounts of viral small interfering (vsi)RNAs, but viral DNA also exhibits a higher amount of cytosine methylation. Whether Ty-1 specifically enhances posttranscriptional gene silencing (PTGS), leading to a degradation of RNA target molecules and primarily relying on 21–22 nucleotides (nts) siRNAs, and/or transcriptional gene silencing (TGS), leading to the methylation of cytosines within DNA target sequences and relying on 24-nts siRNAs, was unknown. In this study, small RNAs were isolated from systemically TYLCV-infected leaves of Ty-1 encoding tomato plants and susceptible tomato Moneymaker (MM) and sequence analyzed. While in susceptible tomato plants vsiRNAs of the 21-nt size class were predominant, their amount was drastically reduced in tomato containing Ty-1. The latter, instead, revealed elevated levels of vsiRNAs of the 22- and 24-nt size classes. In addition, the genomic distribution profiles of the vsiRNAs were changed in Ty-1 plants compared with those from susceptible MM. In MM three clear hotspots were seen, but these were less pronounced in Ty-1 plants, likely due to enhanced transitive silencing to neighboring viral genomic sequences. The largest increase in the amount of vsiRNAs was observed in the intergenic region and the V1 viral gene. The results suggest that Ty-1 enhances an antiviral TGS response. Whether the elevated levels of 22 nts vsiRNAs contribute to an enhanced PTGS response or an additional TGS response involving a noncanonical pathway of RNA dependent DNA methylation remains to be investigated.

Resistance Analysis of CRISPR/Cas9 Genome-Edited Chili M2 Mutant Lines against Pepper Yellow Leaf Curl Viral Disease

<p>Pepper yellow leaf curl virus (PepYLCV) infection transmitted by silverleaf whitefly (Bemisia tabaci [Gennadius]) can decrease chili pepper yield up to 100%. At this moment, there is no chili pepper variety resistant to PepYLCV available. Genome editing approach through CRISPR/Cas9 is an effort to develop variety resistance to the viral infection. The purpose of this study was to obtain M2 lines developed by CRISPR/Cas9 system on proliferating cell nuclear antigen (PCNA) gene for resistance to PepYLCV. A total of four M2 lines (C47-7, L84-2, L84-23, and L120-19) consisting of 60 chili plants were tested for their resistance to PepYLCV. PCR analysis was performed to detect the presence (infection) of the virus. The results showed that a total of 35 plants derived from the four lines were resistant to PepYLCV. They consisted of 7 plants from C47-7 line, 11 plants from L84-2 line, 9 plants from L84-23 line, and 8 plants from L120-19 line. PCR analysis confirmed that the resistant plants obtained from this study were negatively infected by the virus. Since not all tested plants were resistant to virus infection, the PCNA gene allele in these resistant lines were most likely heterozigotes. Sequencing of PCNA gene of the resistant lines is needed to confirm that the resistance phenotypes obtained was due to mutation of the gene. Therefore, further selection needs to be performed to obtain stable and PepYLCV-resistant lines.</p>

Host GRXC6 restricts Tomato yellow leaf curl virus infection by inhibiting the nuclear export of the V2 protein.

Geminiviruses cause serious symptoms and devastating losses in crop plants. With a circular, single-stranded DNA genome, geminiviruses multiply their genomic DNA in the nucleus, requiring the nuclear shuttling of viral proteins and viral genomic DNAs. Many host factors, acting as proviral or antiviral factors, play key roles in geminivirus infections. Here, we report the roles of a tomato glutaredoxin (GRX), SlGRXC6, in the infection of Tomato yellow leaf curl virus (TYLCV), a single-component geminivirus. The V2 protein of TYLCV specifically and preferentially interacts with SlGRXC6 among the 55-member tomato GRX family that are broadly involved in oxidative stress responses, plant development, and pathogen responses. We show that overexpressed SlGRXC6 increases the nuclear accumulation of V2 by inhibiting its nuclear export and, in turn, inhibits trafficking of the V1 protein and viral genomic DNA. Conversely, the silenced expression of SlGRXC6 leads to an enhanced susceptibility to TYLCV. SlGRXC6 is also involved in symptom development as we observed a positive correlation where overexpression of SlGRXC6 promotes while knockdown of SlGRXC6 expression inhibits plant growth. We further showed that SlGRXC6 works with SlNTRC80, a tomato NADPH-dependent thioredoxin reductase, to regulate plant growth. V2 didn’t interact with SlNTRC80 but competed with SlNTR80 for binding to SlGRXC6, suggesting that the V2-disrupted SlGRXC6-SlNTRC80 interaction is partially responsible for the virus-caused symptoms. These results suggest that SlGRXC6 functions as a host restriction factor that inhibits the nuclear trafficking of viral components and point out a new way to control TYLCV infection by targeting the V2-SlGRXC6 interaction.

Tomato Yellow Leaf Curl Virus-Resistant and -Susceptible Tomato Genotypes Similarly Impact the Virus Population Genetics.

Tomato yellow leaf curl virus is a species in the genus Begomovirus and family Geminiviridae. Tomato yellow leaf curl virus (TYLCV) infection induces severe symptoms on tomato plants and causes serious yield losses worldwide. TYLCV is persistently transmitted by the sweetpotato whitefly, Bemisia tabaci (Gennadius). Cultivars and hybrids with a single or few genes conferring resistance against TYLCV are often planted to mitigate TYLCV-induced losses. These resistant genotypes (cultivars or hybrids) are not immune to TYLCV. They typically develop systemic infection, display mild symptoms, and produce more marketable tomatoes than susceptible genotypes under TYLCV pressure. In several pathosystems, extensive use of resistant cultivars with single dominant resistance-conferring gene has led to intense selection pressure on the virus, development of highly virulent strains, and resistance breakdown. This study assessed differences in TYLCV genomes isolated from susceptible and resistant genotypes in Florida and Georgia. Phylogenetic analyses indicated that Florida and Georgia isolates were distinct from each other. Population genetics analyses with genomes field-collected from resistant and susceptible genotypes from Florida and/or Georgia provided no evidence of a genetic structure between the resistant and susceptible genotypes. No codons in TYLCV genomes from TYLCV-resistant or susceptible genotypes were under positive selection, suggesting that highly virulent or resistance-breaking TYLCV strains might not be common in tomato farmscapes in Florida and Georgia. With TYLCV-resistant genotypes usage increasing recently and multiple tomato crops being planted during a calendar year, host resistance-induced selection pressure on the virus remains a critical issue. To address the same, a greenhouse selection experiment with one TYLCV-resistant and susceptible genotype was conducted. Each genotype was challenged with TYLCV through whitefly-mediated transmission serially 10 times (T1-T10). Population genetics parameters at the genome level were assessed at T1, T5, and T10. Results indicated that genomes from resistant and susceptible genotypes did not differentiate with increasing transmission number, no specific mutations were repeatedly observed, and no positive selection was detected. These results reiterate that resistance in tomato might not be exerting selection pressure against TYLCV to facilitate development of resistance-breaking strains. TYLCV populations rather seem to be shaped by purifying selection and/or population expansion.

The Combined Effect of Elevated O3 Levels and TYLCV Infection Increases the Fitness of Bemisia tabaci Mediterranean on Tomato Plants.

Global change and biotic stress, such as tropospheric contamination and virus infection, can individually modify the quality of host plants, thereby altering the palatability of the plant for herbivorous insects. The bottom-up effects of elevated O3 and tomato yellow leaf curl virus (TYLCV) infection on tomato plants and the associated performance of Bemisia tabaci Mediterranean (MED) were determined in open-top chambers. Elevated O3 decreased eight amino acid levels and increased the salicylic acid (SA) and jasmonic acid (JA) content and the gene expression of pathogenesis-related protein (PR1) and proteinase inhibitor (PI1) in both wild-type (CM) and JA defense-deficient tomato genotype (spr2). TYLCV infection and the combination of elevated O3 and TYLCV infection increased eight amino acids levels, SA content and PR1 expression, and decreased JA content and PI1 expression in both tomato genotypes. In uninfected tomato, elevated O3 increased developmental time and decreased fecundity by 6.1 and 18.8% in the CM, respectively, and by 6.8 and 18.9% in the spr2, respectively. In TYLCV-infected tomato, elevated O3 decreased developmental time and increased fecundity by 4.6 and 14.2%, respectively, in the CM and by 4.3 and 16.8%, respectively, in the spr2. These results showed that the interactive effects of elevated O3 and TYLCV infection partially increased the amino acid content and weakened the JA-dependent defense, resulting in increased population fitness of MED on tomato plants. This study suggests that whiteflies would be more successful at TYLCV-infected plants than at uninfected plants in elevated O3 levels.

Chilli leaf curl virus infection downregulates the expression of the genes encoding chloroplast proteins and stress-related proteins.

Virus infection alters the expression of several host genes involved in various cellular and biological processes in plants. Most of the studies performed till now have mainly focused on genes which are up-regulated and later projected them as probable stress tolerant/susceptible genes. Nevertheless, genes which are down-regulated during plant-virus interaction could also play a critical role on disease development as well as in combating the virus infection. Hence, to identify such down-regulated genes and pathway, we performed reverse suppression subtractive hybridization in Capsicum annuum var. Punjab Lal following Chilli leaf curl virus (ChiLCV) infection. The screening and further processing suggested that majority of the genes (approximately 35% ESTs) showed homology with the genes encoding chloroplast proteins and 16% genes involved in the biotic and abiotic stress response. Additionally, we identified several genes, functionally known to be involved in metabolic processes, protein synthesis and degradation, ribosomal proteins, energy production, DNA replication and transcription, and transporters. We also found 3% transcripts which did not show homology with any known genes. The redundancy analysis revealed the maximum percentage of chlorophyll a-b binding protein (15/96) and auxin-binding proteins (13/96). We developed a protein interactome network to characterise the relationships between proteins and pathway involved during the ChiLCV infection. We identified that the most of the interaction occurs either among the chloroplast proteins (Arabidopsis proteins interactive map) or biotic and abiotic stress responsive proteins (Solanum lycopersicum interactome). Taken together, our study provides the first transcriptome and protein interactome of the down-regulated genes during C. annuum-ChiLCV interaction. These resources could be exploited in deciphering the steps involved in the process of virus infection.

Silencing of tomato CTR1 provides enhanced tolerance against Tomato leaf curl virus infection

ABSTRACTTomato leaf curl virus (ToLCV) belonging to Begomovirus family of Geminivirus is known to cause one of the most destructive diseases in tomato. Amongst various ToLCVs, a monopartite Tomato leaf curl Joydebpur virus (ToLCJoV) is most prevalent in eastern part of India. In the present study, we observed induced expression of one of the negative regulators of ethylene signaling pathway gene (LeCTR1) in ToLCJoV infected plants. The Tobacco rattle virus (TRV) induced silencing of the LeCTR1 gene provided enhanced tolerance to ToLCJoV infections. The leaf curling as well as ROS accumulation was significantly reduced in the viral infected LeCTR1 silenced plants. Induction of several defense marker genes (NPR1, PR1, PR5, AOS2, EIN2, EIN3 and ERF5) reinforced enhanced tolerance against ToLCJoV infection in the LeCTR1 silenced tomato. Overall, the present study provides evidence that silencing of LeCTR1 can be deployed to protect tomato from ToLCJoV infections.

Study of biochemical and histopathological changes induced in the sweet pepper (Capsicum annuum L.) in response to Chilli leaf curl virus infection

A survey was conducted at the horticulture field at Lucknow, India and about 64% leaf curl disease incidence was observed on sweet pepper (Capsicum annuum L.) plants. The severe leaf curl disease was observed in several sweet pepper plants causing deterioration of size and quality of fruit. Therefore, this study was undertaken to characterize the pathogen to cause leaf curl disease in sweet pepper and explore the impact of virus disease on fruit quality of sweet pepper plants. The sequence analysis of full-length genome of detected virus and associated betasatellite isolated from the infected plants revealed the occurrence of Chilli leaf curl virus (ChiLCV) in the association of tomato leaf curl Bangladesh betasatellite (ToLCBDB). The sweet pepper seedlings were co-inoculated with agroinfectious DNA clones of ChiLCV and ToLCBDB which developed similar leaf curl symptom as was observed naturally. The higher accumulation of proline, malondialdehyde, sugar, and polyphenols were observed in virus infected plants as compared to the control. The activities of defense-related enzymes (APx, GPx and SOD) were elevated to cope with the virus-induced stress in infected plants. The fruits in infected plants was deformed compared to control and the nutritional quality of fruits in infected plants was compromised as carotenoids and vitamin-C contents reduced significantly. Moreover, the histopathological evaluations of these symptomatic plants suggested that virus infection severely affects the vascular tissue of leaf and stem. The phenomenon of alterations in the stress related biochemicals of sweet pepper plants due to ChiLCV infection is demonstrated which measures the fruit quality deteriorated by this interaction.