Trans-Complementation of Long-Distance Movement of White clover mosaic virus Triple Gene Block (TGB) Mutants: Phloem-Associated Movement of TGBp1

Abstract

The triple gene block proteins (TGBp1-3) and coat protein (CP) of potexviruses are required for cell-to-cell movement. Both cell-to-cell and long-distance movement of White clover mosaic virus in which individual, combinations, or all movement functions were mutated could be rescued by transgenic Nicotiana benthamiana expressing complementary viral products. To address the importance of TGB functions in vascular transport, we used an experimental system based on grafted plants and trans-complementation, to define co-translocated viral products and the minimal requirements for viral exit from the plant vasculature. Evidence is presented that TGBp1 is co-translocated with viral RNA and CP and that, once viral RNA is loaded into the phloem translocation stream, it can exit in sink tissues and replicate in the absence of TGBp2-3. These results are discussed in the context of the recent finding that TGBp1 can mediate the suppression of signaling involved in systemic gene silencing.

Mixed Infections ofPepino Mosaic VirusStrains Modulate the Evolutionary Dynamics of this Emergent Virus

“…ORFs 2, 3, and 4 encode the triple gene block (TGB) proteins TGBp1, TGBp2, and TGBp3, which are essential for virus movement (46,75,78). Potato virus X TGBp1 is a multifunctional protein that induces plasmodesmal gating, moves from cell to cell, has ATPase and RNA helicase activities, binds viral RNAs, and acts as suppressor of RNA silencing (39,(76)(77)(78). ORF5 encodes the coat protein (CP) which, in addition to its structural role, is required for cell-to-cell and long-distance movement (12).…”

Análisis funcional y localización subcelular de las proteínas implicadas en el movimiento intra e intercelular del virus de las manchas necróticas del melón (MNSV)

“…In this sense, p42 can contribute to development of lesions indirectly by facilitating virus replication and spreading. Interestingly and in parallel to our observations, with regard to the p7B component of the DGBp, a weak RNA suppressor activity was initially described in agro-infiltration experiments for Potato virus X p25, protein 1 from the triple gene block of proteins which are required for cell-to-cell movement of potexviruses Lough et al, 2001). These data suggest that PTGS could be controlled by a component of the cell-to-cell movement machinery as a common feature among a number of plant viruses whose silencing suppression might be linked to viral transport …”

“…Así pues, la participación de p42 promoviendo el transporte intercelular probablemente sea una consecuencia indirecta de contrarrestar los mecanismos de defensa del huésped y por tanto, no exista una implicación directa de la p42 en el mecanismo molecular encargado del transporte de los genomas virales. Se ha descrito esta función para la proteína p25 de PVX, la TGBp1 del bloque de tres genes (TGB) de Potexvirus Lough et al, 2001) que, al igual que p7B (DGBp1), está a su vez implicada en el movimiento célula a célula del virus. Estos últimos datos sugieren que los factores virales que controlan el movimiento intra-e intercelular pueden tener a su vez actividad de supresión del PTGS (Verchot-Lubicz, 2005), aunque los estudios realizados hasta ahora no permiten determinar la etapa exacta del silenciamiento de RNA que se vería afectada por estas proteínas del MNSV.…”

Desarrollo De Un Vector Para La Expresión Simultánea De Múltiples Proteínas en Plantas Basado en El Potyvirus Del Grabado Del Tabaco

“…Proteínas como P1, HC-Pro y P3 se han transferido a plantas con éxito para distintos tipos de estudios de biología básica, análisis de resistencia o ensayos de sinergismo con los potyvirus (Verchot y Carrington, 1995;Vance et al, 1995;Moreno et al, 1998), así como algunas proteínas de otros virus también se han podido complementar en trans (Lough et al, 2001). En la mayoría de esos casos se ha estudiado la posibilidad de suplementar genes individuales, mientras que en el presente estudio se comprobó que es posible suplementar en trans más de un gen del TEV.…”