Identification and Functional Analysis of Four RNA Silencing Suppressors in Begomovirus Croton Yellow Vein Mosaic Virus

Croton yellow vein mosaic virus (CYVMV), a species in the genus Begomovirus, is a prolific monopartite begomovirus in the Indian sub-continent. CYVMV infects multiple crop plants to cause leaf curl disease. Plants have developed host RNA silencing mechanisms to defend the threat of viruses, including CYVMV. We characterized four RNA silencing suppressors, namely, V2, C2, and C4 encoded by CYVMV and betasatellite-encoded C1 protein (βC1) encoded by the cognate betasatellite, croton yellow vein betasatellite (CroYVMB). Their silencing suppressor functions were verified by the ability of restoring the β-glucuronidase (GUS) activity suppressed by RNA silencing. We showed here for the first time that V2 was capable of self-interacting, as well as interacting with the V1 protein, and could be translocalized to the plasmodesmata in the presence of CYVMV. The knockout of either V2 or V1 impaired the intercellular mobility of CYVMV, indicating their novel coordinated roles in the cell-to-cell movement of the virus. As pathogenicity determinants, each of V2, C2, and C4 could induce typical leaf curl symptoms in Nicotiana benthamiana plants even under transient expression. Interestingly, the transcripts and proteins of all four suppressors could be detected in the systemically infected leaves with no correlation to symptom induction. Overall, our work identifies four silencing suppressors encoded by CYVMV and its cognate betasatellite and reveals their subcellular localizations, interaction behavior, and roles in symptom induction and intercellular virus movement.

Molecular Characterization and Transmission Study of the Begomovirus on Hollyhock Plant Causing Leaf Curl Disease for the First Time in Province Punjab, Pakistan

I. Background: Hollyhock (Alcea rosea) is an ornamental plant belonging to the Malvaceae family and has a remarkable aesthetic and medicinal value. Previously in Pakistan, the hollyhock plant was not found to be infected by begomovirus and the plant first time showed the symptoms of typical leaf curling, puckering as well as thickened veins. II. Methods and Results: During the year 2018, symptomatic samples of the hollyhock plants were collected that exhibited characteristic typical leaf curling, puckering as well as thickened veins. DNA was extracted from the samples and the PCR technique was optimized for the detection of begomovirus followed by sequencing. The samples were detected to be infected with begomovirus by using Av/Ac core, Begomo 01/02, and CLCV 01/02 primer showed positive results with 579bp, 2.8kb, and 1.1kb nucleotide respectively. The betasatellite was amplified by using beta01/02 and CLCuMuBF11/R33 showed positive results with 1400bp and 481bp respectively. Sequencing results showed that diseased hollyhock plants were associated with Cotton leaf curl Multan virus-Rajasthan strain along with Cotton leaf curl Multan betasatellite. III. Conclusion: Hollyhock plants infected by begomovirus has been reported for the first time as a possible source of virus inoculum from Pakistan.

Diverse Regulations of Viral and Host Genes in Tomato Germplasms Responding to Tomato Yellow Leaf Curl Virus Inoculation

Tomato yellow leaf curl virus (TYLCV) is the dominating pathogen of tomato yellow leaf curl disease that caused severe loss to tomato production in China. In this study, we found that a TYLCV-resistant tomato line drastically reduced the accumulation of viral complementary-sense strand mRNAs but just moderately inhibit that of viral DNA and virion-sense strand mRNAs. However, two other resistant lines did not have such virus inhibition pattern. Analysis of differential expressed genes showed that the potential host defense-relevant processes varied in different resistant tomatoes, as compared to the susceptible line, suggesting a diversity of tomato TYLCV-resistance mechanisms.

Alternations in Biochemical Components in Chilli (Capsicum annuum L.) Plants Infected with Chilli Leaf Curl Viral Disease

Chilli (Capsicum annuum L.) is an important spice crop grown all over the world. Chilli leaf curl, a viral disease outbreak in almost every chilli grown area causing significant yield losses. An experiment was conducted to analyze the biochemical changes in infected and healthy plant of chilli. The chlorophyll a, b and total were highest in healthy leaves then infected leaves. Moreover, severely infected leaves have lower amounts of chlorophyll contents. Out of nine cultivars total phenol and tannin contents were found maximum in Gucchedar, POL-75 and Byddagi Kaddi in comparison to highly susceptible cultivars Musa Badi, Phuley Joyti and NPKT-2.

Complete Genome Sequences of Tomato Leaf Curl Guam Virus, a Novel Tomato-Infecting Begomovirus from Guam, USA

Genome sequences of a novel begomovirus infecting tomato on Guam were obtained using primer-walking and sequencing. The complete genome sequences are 2,750 nucleotides long with a typical monopartite organization and display less than 91% nucleotide sequence identity to other begomoviruses. A provisional name, tomato leaf curl Guam virus (ToLCGuV), is proposed.