Movement of rice yellow mottle virus between xylem cells through pit membranes

Abstract

The translocation of rice yellow mottle virus (RYMV) within tissues of inoculated and systemically infected Oryza sativa L. leaves was characterized by Western immunoblotting, Northern blotting, and electron microscopy of thin sections. In inoculated leaves, RYMV RNA and coat protein first were detected at 3 and 5 days postinoculation, respectively. By 6 days postinoculation, RYMV had spread systemically to leaves, and virus particles were observed in most cell types, including epidermal, mesophyll, bundle sheath, and vascular parenchyma cells. Most of the virions accumulated in large crystalline patches in xylem parenchyma cells and sieve elements. Colocalization of a cell wall marker for cellulosic ␤-(1-4)-D-glucans and anti-RYMV antibodies over vessel pit membranes suggests a pathway for virus migration between vessels. We propose that the partial digestion of pit membranes resulting from programmed cell death may permit virus migration through them, concomitant with autolysis. In addition, displacement of the Ca 2؉ from pit membranes to virus particles may contribute to the disruption of the pit membranes and facilitate systemic virus transport.

Analysis of the systemic colonization of cucumber plants by Cucumber green mottle mosaic virus

“…Xylem transport in steamed plants was temperature dependent and inefficient, as deduced from the low percentage of steamed plants that became systemically infected (about 11 %) and from the delay in infection compared with untreated controls (Table 3). Long-distance movement through the xylem has been proposed for some viruses, but few reports have addressed this issue directly (Chambers & Francki, 1966;Dubois et al, 1994;Jones, 1975;Opalka et al, 1998;Schneider & Worley, 1959a, b;Verchot et al, 2001). Xylem localization of virus particles has been reported for a number of viruses and hosts (e.g.…”

“…A current hypothesis is that calcium binding by virus particles will disrupt pit membranes between mature and differentiating xylem vessels or tracheids, so enabling the virus to traffic through the membrane. This hypothesis was proposed on the basis of immunochemical analyses of the colonization of rice plants by Rice yellow mottle virus (Opalka et al, 1998) and on the well-known role of calcium in the stabilization of Sobemovirus isometric capsids (Hsu et al, 1976;Opalka et al, 2000). It is known that calcium binding stabilizes TMV particles (Gallagher & Lauffer, 1983;Namba et al, 1989), and putative calcium binding sites have been described for CGMMV, watermelon strain (Wang & Stubbs, 1994), which has the same amino acid sequence in the CP as the SH strain (Ugaki et al, 1991).…”

Ultrastructural studies of plasmodesmatal and vascular translocation of tobacco rattle virus (TRV) in tobacco and potato

“…Moreover, virions without coat protein could also leave the conductive tissue in systemically infected leaves. Xylem transport by plant viruses was originally proposed in the studies of Sobemoviruses such as Rice yellow mottle virus (RYMV) and Blueberry shoestring virus (Opalka et al 1998;Urban et al 1989). In immunogold labelling studies using light and electron microscopy, Beet necrotic yellow vein virus (BNYVV) and Soilborne wheat mosaic virus (SBWMV) were each detected in xylem vessels or xylem parenchyma in infected plant roots (Dubois et al 1994;Verchot et al 2001).…”

Membrane-associated virus replication complexes locate to plant conducting tubes

“…Upon apoptosis, these become hollow vessels, thereby releasing viruses into the water flow. 8 Viral uploading into xylem parenchymal cells would then take place through pit membranes. 8,9 Both virus particles and yetto-be-defined RNP complexes have been implicated as the unit for plant virus long-distance movement.…”

“…8 Viral uploading into xylem parenchymal cells would then take place through pit membranes. 8,9 Both virus particles and yetto-be-defined RNP complexes have been implicated as the unit for plant virus long-distance movement. Virus particles have been detected in phloem sieve elements [10][11][12][13] and phloem sap, 14,15 as well as in the xylem vessel elements Keywords: apoplast, membrane-bound replication complexes, phloem, paramural vesicles, TuMV, xylem and guttation fluid.…”