Project description:RNA interference (RNAi) is a conserved, RNA-mediated, regulatory mechanism in eukaryotes. In plants, it plays an important role in growth, development and resistance against viral infections. As a counter-defence, plant viruses, e.g. geminiviruses, encode RNAi suppressors, such as AC2, AC4 and AV2. To obtain Nicotiana tabacum virus resistant plants against Tomato leaf curl New Delhi virus (ToLCNDV), we employ the biogenesis pathway of a class of endogenous siRNAs, the trans-acting siRNAs (ta-siRNAs), by engineering artificial ta-siRNAs (ata-siRNAs) targeting the AC2 (TRiV-AC2) and AC4 (TRiV-AC4) RNAi suppressors using miRNA390 dual target sites. The mode of action of ta-siRNAs comprises of the cleavage of the target (similar to the miRNA targeting). Using degradome approaches, the abundance of the resulting 3' fragment of the cleaved transcript can be quantified and the precise localization of the cleavage on the target mRNA can be identified. We sequenced degradome libraries of Nicotiana tabacum plants infected with ToLCNDV which were treated with the ata-siRNA-AC2 construct; mock-treated plants were used as controls. Following quality checks, the abundance distributions of the degradation fragments were normalized. The transcripts with different cleavage patterns was the AC2, supporting the conclusion that an efficient cleavage of the target occurred, without significant off-target effects.
Project description:RNA interference (RNAi) is a conserved, RNA-mediated, regulatory mechanism in eukaryotes. In plants, it plays an important role in growth, development and resistance against viral infections. As a counter-defence, plant viruses, e.g. geminiviruses, encode RNAi suppressors, such as AC2, AC4 and AV2. To obtain Nicotiana tabacum virus resistant plants against Tomato leaf curl New Delhi virus (ToLCNDV), we employ the biogenesis pathway of a class of endogenous siRNAs, the trans-acting siRNAs (ta-siRNAs), by engineering artificial ta-siRNAs (ata-siRNAs) targeting the AC2 (TRiV-AC2) and AC4 (TRiV-AC4) RNAi suppressors using miRNA390 dual target sites. The mode of action of ta-siRNAs comprises of the cleavage of the target (similar to the miRNA targeting). Using degradome approaches, the abundance of the resulting 3' fragment of the cleaved transcript can be quantified and the precise localization of the cleavage on the target mRNA can be identified. We sequenced degradome libraries of Nicotiana tabacum plants infected with ToLCNDV which were treated with the ata-siRNA-AC2 construct; mock-treated plants were used as controls. Following quality checks, the abundance distributions of the degradation fragments were normalized. The transcripts with different cleavage patterns was the AC2, supporting the conclusion that an efficient cleavage of the target occurred, without significant off-target effects.
Project description:We investigated the transcriptional response of invasive B. tabaci B biotype to tomato yellow leaf curl China virus (TYLCCNV) using Illumina sequencing technology. We found that 1,606 genes involved in 157 biochemical pathways were differentially expressed in the viruliferous whiteflies.
Project description:RNA interference (RNAi) is a widely-used approach to generate virus-resistant transgenic crops. However, durability of RNAi-mediated resistance under extreme field conditions and side-effects of stable RNAi expression have not been thoroughly investigated. Here we performed field trials and molecular characterization of two RNAi-transgenic Solanum lycopersicum lines resistant to Tomato yellow leaf curl virus (TYLCV) disease, the major constraint for tomato cultivation in Cuba and worldwide. In order to determine potential impact of the hairpin RNA transgene expression on tomato genome expression and development, differences in the phenotypes and the transcriptome profiles between the transgenic and non-transgenic plants were examined. Transcriptome profiling revealed a common set of up- and down-regulated tomato genes, which correlated with slight developmental abnormalities in both transgenic lines.
Project description:During 2006, pumpkin leaf curl-a new disease was observed in the experimental field at Indian Agricultural Research Institute. The disease was characterized by upward leaf curl with chlorotic patches and stunting of plant. Polymerase chain reaction (PCR) with coat protein specific primers to Tomato leaf curl New Delhi virus (ToLCNDV) indicated association of a begomovirus with the disease. The sequence comparison and phylogenetic analysis of the complete DNA genome further revealed the identity of the virus as ToLCNDV. The study provides evidence that ToLCNDV is associated with the leaf curl of pumpkin (Cucurbita moschata) in northern India.
Project description:BackgroundBegomoviruses are whitefly-transmitted geminiviruses with genomes that consist of either two components (known as DNA A and DNA B) or a single component (homologous to the DNA A component of bipartite begomoviruses). Monopartite begomoviruses are often associated with a symptom-modulating DNA satellite (collectively known as betasatellites). Both bipartite and monopartite begomoviruses with associated satellites have previously been identified in chillies showing leaf curl symptoms in Pakistan.ResultsA chilli plant (Capsicum annum) with chilli leaf curl disease symptoms was found to contain a begomovirus, a betasatellite and the DNA B component of Tomato leaf curl New Delhi virus (ToLCNDV). The begomovirus consisted of 2747 nucleotides and had the highest sequence identity (99%) with Pepper leaf curl Lahore virus (PepLCLV-[PK: Lah:04], acc. no. AM404179). Agrobacterium-mediated inoculation of the clone to Nicotiana benthamiana, induced very mild symptoms and low levels of viral DNA, detected in systemically infected leaves by PCR. No symptoms were induced in Nicotiana tabacum or chillies either in the presence or absence of a betasatellite. However, inoculation of PepLCLV with the DNA B component of ToLCNDV induced leaf curl symptoms in N. benthamiana, N. tabacum and chillies and viral DNA accumulated to higher levels in comparison to plants infected with just PepLCLV.ConclusionsBased on our previous efforts aimed at understanding of diversity of begomoviruses associated with chillies, we propose that PepLCLV was recently mobilized into chillies upon its interaction with DNA B of ToLCNDV. Interestingly, the putative rep-binding iterons found on PepLCLV (GGGGAC) differ at two base positions from those of ToLCNDV (GGTGTC). This is the first experimental demonstration of the infectivity for a bipartite begomovirus causing chilli leaf curl disease in chillies from Pakistan and suggests that component capture is contributing to the emerging complexity of begomovirus diseases in the region.
Project description:Viruses of the genus Begomovirus (family Geminiviridae) are economically important phytopathogens that are transmitted plant-to-plant by the whitefly Bemisia tabaci. Most Old World (OW) begomoviruses are monopartite and many of these interact with symptoms and host range determining betasatellites. Tomato leaf curl New Delhi virus (ToLCNDV) is one of only a few OW begomoviruses with a bipartite genome (components known as DNA A and DNA B). Four genes [AV2, coat protein (CP), transcriptional-activator protein (TrAP), and AC4] of ToLCNDV were mutated and the effects of the mutations on infectivity, symptoms and the ability to maintain Cotton leaf curl Multan betasatellite (CLCuMuB) were investigated. Infectivity and virus/betasatellite DNA titer were assessed by Southern blot hybridization, PCR, and quantitative PCR. The results showed TrAP of ToLCNDV to be essential for maintenance of CLCuMuB and AV2 to be important only in the presence of the DNA B. AC4 was found to be important for the maintenance of CLCuMuB in the presence of, but indispensable in the absence of, the DNA B. Rather than being required for maintenance, the CP was shown to possibly interfere with maintenance of the betasatellite. The findings show that the interaction between a bipartite begomovirus and a betasatellite is more complex than just trans-replication. Clearly, multiple levels of interactions are present and such associations can cause additional significant losses to crops although the interaction may not be stable.