These findings identify DNA-B as a major determinant of tomato infectivity and reveal an essential role for CP in systemic movement of the Mediterranean ToLCNDV isolate.
Abstract
Tomato leaf curl New Delhi virus (ToLCNDV) is a bipartite begomovirus with a broad host range and marked geographic variation in host adaptation. Whereas Asian isolates readily infect solanaceous crops, Mediterranean isolates are mainly adapted to cucurbits and infect tomato poorly. The molecular basis of this divergence remains unclear. Here, we compared Indian (ToLCNDV-IN) and Spanish (ToLCNDV-ES) isolates using reciprocal pseudo-recombinants to infect Solanum lycopersicum and Nicotiana benthamiana. Both DNA-A components replicated in tomato leaves, indicating that the inability of ToLCNDV-ES to infect tomato is not due to defective replication. Pseudo-recombinant analyses revealed that the DNA-B-IN component efficiently supported systemic infection of the heterologous DNA-A-ES, whereas the reciprocal combination established systemic infection only at low frequency. Furthermore, DNA-A from the IN isolate was unable, or only rarely able, to establish systemic infection in tomato in the absence of DNA-B, demonstrating a strict requirement for DNA-B-mediated movement functions. In N. benthamiana, all viral combinations systemically infected plants. Although both DNA-A components were capable of systemic infection without DNA-B in this host, viral accumulation was significantly reduced compared with bipartite infections, indicating that DNA-B enhances infection efficiency but is not essential for long-distance movement. Unexpectedly, a coat protein (CP)-mutated version of ToLCNDV-ES failed to establish systemic infection in N. benthamiana and Cucumis melo despite normal replication, revealing an essential role for CP in systemic movement. Collectively, our findings identify DNA-B as a major determinant of tomato infectivity and reveal an essential role for CP in systemic movement of the Mediterranean ToLCNDV isolate.
Tomato spotted wilt virus (TSWV) is an economically devastating pathogen that rapidly overcomes genetic resistance in major crops. Reverse genetic systems are crucial for investigating plant-virus interactions and resistance breaking mechanisms, and developing these tools for segmented ambisense RNA viruses remains a crucial challenge. Current TSWV-clones rely on extensively modified Asian isolates requiring co-delivery of multiple replication helpers and viral silencing suppressors. Streamlining these systems for regionally significant strains with minimal genetic alterations is essential. Here we developed the first infectious clone of a USA TSWV isolate (PA01). Three binary plasmids contain cDNAs for the antigenomic L and S segments, and the genomic M segment, with enhanced GFP replacing NSs on the S segment. Co-delivery of the cucumovirus 2b alone or in combination with tombusvirus P19 or begomovirus AL2, achieved a high proportion of systemically infected Nicotiana benthamiana and Capsicum annuum plants. In N. tabacum, co-delivering the Caenorhabditis elegans cell death suppressor CED-9, or using NahG transgenic plants produced 20 to 62% systemically infected plants. These data indicate that in addition to the anti-viral RNA silencing machinery, additional host defense pathways influence TSWV rescue and systemic infection from cDNA.
Haden Ball, O. Atallah, H. García-Ruíz et al.· Molecular Plant-Microbe Inte...· 0 citations
The presence of new strains of geminiviruses infecting tomato plants, which have single genomic component and molecular diversity of Tamil Nadu region, are revealed.
M. Deivamani, S. Rageshwari, V. Satya et al.· Genetics and Molecular Resea...· 0 citations
BACKGROUND
Begomoviruses are circular single-stranded DNA viruses transmitted by the whitefly Bemisia tabaci and are major causal agents of leaf curl disease in tomato (Solanum lycopersicum L.). The present study aimed to comprehensively characterize the virome associated with symptomatic tomato plants collected from major agro-ecological regions of Tamil Nadu, India, using high-throughput sequencing (HTS).
RESULTS
HTS based virome analysis of tomato plants exhibiting severe leaf curl symptoms revealed a complex viral community. The virosphere includes multiple begomoviruses, namely tomato leaf curl New Delhi virus (ToLCNDV), tomato leaf curl Bangalore virus (ToLCBaV), tomato leaf curl Karnataka virus, and chilli leaf curl virus (ChiLCV), along with associated alpha- and betasatellites. In addition, RNA viruses including pepper virus A (PepVA), chilli veinal mottle virus (ChiVMoV), and tomato chlorosis virus (ToCV) were also identified, indicating frequent occurrence of mixed infections. Full-length or coding-complete genome sequences were recovered for most viral components, whereas partial contigs were obtained for Southern tomato virus (STV) and tobacco vein distorting virus (TVDV). Notably, a novel recombinant monopartite begomovirus, tentatively named tomato leaf curl Dindigul virus (ToLCDiV), showed < 89.82% nucleotide identity with known begomovirus sequences. In addition, a distinct alphasatellite, tomato leaf curl Madurai alphasatellite (ToLCMdA) showed 86.74% nucleotide identity with known alphasatellites, supporting its distinctiveness based on ICTV species demarcation criteria. Recombination analysis suggested that ToLCDiV may have originated from parental lineages related to ToLCBaV and tomato leaf curl Gujarat virus (ToLCGV), with recombination breakpoints in the AC1, AC4, and intergenic regions.
CONCLUSION
This study revealed a complex tomato virome associated with leaf curl disease in Tamil Nadu, driven by mixed viral infections and recombination. The detection of the putative novel recombinant begomovirus ToLCDiV and distinct alphasatellite ToLCMdA highlights the emergence of new virus-satellite components and emphasizes the need for continued virome surveillance and integrated disease management in tomato production systems.
M. R K, Kavi Sidharthan V, Nagendran Krishnan et al.· BMC Plant Biology· 0 citations
This review examines the defence strategies of rice and provides key insights into host-pathogen interactions that inform the development of durable resistance and improved disease management strategies, including integrating molecular breeding with sustainable agricultural practices to mitigate yield losses caused by BLB.
M. Syed, N. Rajinimala, M. Theradimani et al.· Plant Science Today· 0 citations
Viral coat protein (CP)-mediated resistance represents an effective strategy that confers robust antiviral defense in plants. However, the functional relevance of this resistance mechanism during mixed infections by distinct viral species remains largely elusive. Mixed viral infections in agricultural crops frequently lead to exacerbated disease symptoms and substantial yield losses, posing a severe threat to global agricultural production. In this study, we demonstrate that expression of tomato leaf curl New Delhi virus (ToLCNDV) CP confers effective resistance against tomato yellow leaf curl China virus (TYLCCNV), another prominent geminivirus. Strikingly, the βC1 protein encoded by TYLCCNV betasatellite can fully counteract this CP-mediated resistance through direct interaction with ToLCNDV CP and promotion of its proteasome-dependent degradation. We further identified the residue Tyr110 of βC1 as essential for the interaction and subsequent CP degradation. Consequently, βC1-mediated suppression of CP resistance promotes efficient systemic infection of ToLCNDV DNA A. Collectively, our results uncover a novel mechanism by which a viral effector antagonizes viral CP-mediated host resistance during mixed viral infections, offering important insights into viral pathogenesis and the development of sustainable disease control strategies.
Shi Wu, Yuzhen Mei, Yuan Chen et al.· Phytopathology Research· 0 citations