RESUMEN
Tobraviruses, like other (+) stranded RNA viruses of plants, replicate their genome in cytoplasm and use such usual membranous structures like endoplasmic reticulum. Based on the ultrastructural examination of Tobacco rattle virus (TRV)-infected potato and tobacco leaf tissues, in this work we provide evidence of the participation of not only the membranous and vesicular ER structures but also other cell organelles during the viral infection cycle. Non-capsidated TRV PSG particles (potato isolate from the Netherlands) (long and short forms) were observed inside the nucleus while the presence of TRV capsid protein (CP) was detected in the nucleus caryolymph and within the nucleolus area. Both capsidated and non-capsidated viral particles were localized inside the strongly disorganized chloroplasts and mitochondria. The electron-dense TRV particles were connected with vesicular structures of mitochondria as well as with chloroplasts in both potato and tobacco tissues. At 15-30 days after infection, vesicles filled with TRV short particles were visible in mitochondria revealing the expanded cristae structures. Immunodetection analysis revealed the TRV PSG CP epitope inside chloroplast with disorganized thylakoids structure as well as in mitochondria of different tobacco and potato tissues. The ultrastructural analysis demonstrated high dynamics of the main cell organelles during the TRV PSG-Solanaceous plants interactions. Moreover, our results suggest a relationship between organelle changes and different stages of virus infection cycle and/or particle formation.
Asunto(s)
Retículo Endoplásmico/ultraestructura , Orgánulos/ultraestructura , Orgánulos/virología , Enfermedades de las Plantas/virología , Virus de Plantas/fisiología , Virus ARN/fisiología , Proteínas de la Cápside/aislamiento & purificación , Núcleo Celular/ultraestructura , Núcleo Celular/virología , Cloroplastos/ultraestructura , Cloroplastos/virología , Retículo Endoplásmico/virología , Células del Mesófilo/ultraestructura , Células del Mesófilo/virología , Microscopía Electrónica de Transmisión , Mitocondrias/ultraestructura , Mitocondrias/virología , Floema/ultraestructura , Floema/virología , Hojas de la Planta/virología , Virus de Plantas/ultraestructura , Virus ARN/ultraestructura , Solanum tuberosum/virología , Nicotiana/virologíaRESUMEN
Plant viruses cause a variety of diseases in susceptible hosts. The disease symptoms often include leaf malformations and other developmental abnormalities, suggesting that viruses can affect plant development. However, little is known about the mechanisms underlying virus interference with plant morphogenesis. Here, we show that a C-4 type zinc-finger (ZF) protein, p12, encoded by a carlavirus (chrysanthemum virus B) can induce cell proliferation, which results in hyperplasia and severe leaf malformation. We demonstrate that the p12 protein activates expression of a regulator of cell size and proliferation, designated upp-L (upregulated by p12), which encodes a transcription factor of the basic/helix-loop-helix family sufficient to cause hyperplasia. The induction of upp-L requires translocation of the p12 protein into the nucleus and ZF-dependent specific interaction with the conserved regulatory region in the upp-L promoter. Our results establish the role of the p12 protein in modulation of host cell morphogenesis. It is likely that other members of the conserved C-4 type ZF family of viral proteins instigate reprogramming of plant development by mimicking eukaryotic transcriptional activators.
Asunto(s)
Factores de Transcripción con Motivo Hélice-Asa-Hélice Básico/metabolismo , Carlavirus/patogenicidad , Proliferación Celular , Tamaño de la Célula , Chrysanthemum/virología , Nicotiana/metabolismo , Transporte Activo de Núcleo Celular , Factores de Transcripción con Motivo Hélice-Asa-Hélice Básico/genética , Carlavirus/genética , Carlavirus/metabolismo , Núcleo Celular/metabolismo , Núcleo Celular/virología , Chrysanthemum/genética , Chrysanthemum/metabolismo , Células del Mesófilo/metabolismo , Células del Mesófilo/virología , Datos de Secuencia Molecular , Células Vegetales/metabolismo , Desarrollo de la Planta , Enfermedades de las Plantas/virología , Hojas de la Planta/citología , Hojas de la Planta/metabolismo , Hojas de la Planta/virología , Proteínas de Plantas/genética , Proteínas de Plantas/metabolismo , Regiones Promotoras Genéticas , Nicotiana/genética , Nicotiana/virología , Proteínas Virales/genética , Proteínas Virales/metabolismo , Dedos de ZincRESUMEN
Cell-to-cell trafficking of RNA is an emerging biological principle that integrates systemic gene regulation, viral infection, antiviral response, and cell-to-cell communication. A key mechanistic question is how an RNA is specifically selected for trafficking from one type of cell into another type. Here, we report the identification of an RNA motif in Potato spindle tuber viroid (PSTVd) required for trafficking from palisade mesophyll to spongy mesophyll in Nicotiana benthamiana leaves. This motif, called loop 6, has the sequence 5'-CGA-3'...5'-GAC-3' flanked on both sides by cis Watson-Crick G/C and G/U wobble base pairs. We present a three-dimensional (3D) structural model of loop 6 that specifies all non-Watson-Crick base pair interactions, derived by isostericity-based sequence comparisons with 3D RNA motifs from the RNA x-ray crystal structure database. The model is supported by available chemical modification patterns, natural sequence conservation/variations in PSTVd isolates and related species, and functional characterization of all possible mutants for each of the loop 6 base pairs. Our findings and approaches have broad implications for studying the 3D RNA structural motifs mediating trafficking of diverse RNA species across specific cellular boundaries and for studying the structure-function relationships of RNA motifs in other biological processes.