Capsicum frutescens (chilli) plants exhibiting leaf curl symptoms, collected from Palampur, Himachal Pradesh region of India, were found associated with a begomovirus and a betasatellite‐like molecule. Viral DNA was amplified, cloned and sequenced. The begomoviral genome and the betasatellite consisted of 2775 and 1376 nucleotides respectively. The virus appeared to be monopartite. The genome sequence had <87·9% identity with all other begomovirus sequences, below the threshold for species demarcation, suggesting that the isolate represents a distinct species for which the name Chilli leaf curl Palampur virus (ChiLCPaV) is proposed. Infectious clones consisting of partial tandem repeats of the viral genome (1·9‐mer) and the betasatellite (1·7‐mer) were constructed in the binary vector pCAMBIA‐1300 and agroinoculated to chilli and Nicotiana benthamiana . The viral clone did not produce leaf curl symptoms when inoculated alone but the plants were stunted compared to controls. Typical leaf curling and stunting symptoms were observed when the viral clone was inoculated with the betasatellite. In a phylogenetic analysis with other closely related begomoviruses, the new sequence grouped with an isolate of Papaya leaf curl virus ‐[Pakistan:2008] from Rhynchosia capitata and Tomato leaf curl New Delhi virus‐ [India:2006] from tomato. The betasatellite showed most identity (94%) with an isolate of Chilli leaf curl betasatellite from Pakistan. Using the rdp3 recombination detection program, a recombination event involving Croton yellow vein mosaic virus ‐[India:2007] as a major parent and Tomato leaf curl Karnataka virus ‐[India:2007] as a minor parent was detected in the ChiLCPaV sequence. No significant recombination event was detected in the betasatellite sequence.

Tomato leaf curl Palampur virus (ToLCPalV) is a whitefly-transmitted, bipartite begomovirus. Here, we demonstrated that ectopic expression of AV2 from a Potato virus X (PVX)-based vector accelerated systemic necrosis and reactive oxygen species (ROS) accumulation in Nicotiana benthamiana. Furthermore, 10 amino acids from N-terminal region of AV2 were found to be associated with the systemic necrosis symptom/phenotype. Mutational studies of ToLCPalV infectious clones lacking the AV2 revealed that AV2 is essential for the systemic movement of DNA-A, symptom severity and viral DNA accumulation. In a yeast two-hybrid assay, Catalase2 (Cat2) was found to associate with AV2 protein. Further, silencing of Cat2 resulted in appearance of necrotic lesions on N. benthamiana and these plants were highly susceptible to ToLCPalV infection in comparison to control plants. Infection ToLCPalV on Solanum lycopersicum resulted in downregulation of Cat2 transcripts, followed by accumulation of ROS and stress marker transcripts. The AV2 protein also suppressed virus-induced gene silencing (VIGS) of the Phytoene desaturase (PDS) gene. Our results show that AV2 is essential for the pathogenicity, systemic movement and suppression of gene silencing in the host. Altogether, our findings suggest that interactions between AV2 and Cat2 might play a crucial role in the establishment of ToLCPalV infection.

Nucleic acid transfer between plants is a phenomenon which is likely to occur in many ways in nature. We report here the active transmission of Apple scar skin viroid (ASSVd) naked ssRNA species by the whitefly Trialeurodes vaporariorum (Tv). Not only the viroid RNA, its DNA form was also identified from the insect. The viroid transfer efficiency was enhanced with the help of Cucumis sativus Phloem protein 2 (CsPP2), a plant protein known to translocate viroid RNAs. This PP2/ASSVd complex is stably present in the viroid infected cucumber plants, as was identified with the help of immunological reaction. As viroid-like secondary structures are found in some plant RNAs, and PP2 is known to bind and translocate several RNAs, the results have huge implications in transfer of these RNA species between plants visited by the whitefly.