Tobamovirus and Potyvirus Accumulation in Minor Veins of Inoculated Leaves from Representatives of the Solanaceae and Fabaceae

Accumulation of genomic TMV RNA in cells of a category V vein (defined in Fig. 1 legend) from a mature inoculated leaf of Xanthi at 4 dpi. A, Section from an inoculated leaf analyzed by in situ hybridization using a biotinylated-RNA probe complementary to nucleotides 1 to 3332 of the TMV genome. The biotinylated-RNA probe was then detected using a streptavidin-gold conjugate followed by silver enhancement. The section was photographed under a light microscope. The labeling signal appears as white specks in cells in the dark-field image. Three VP cells and one C cell of the vein had accumulated viral RNA. The infected C cell is denoted with an arrow. B, Section from a mock-inoculated Xanthi leaf analyzed as for the vein in A. TMV RNA was not detected in vein cells from this section. Bars = 12 μm.

Accumulation of TMV in cells of a typical category V vein (defined in Fig. 1) from a mature inoculated leaf ofC. annuum at 3 dpi. TMV accumulation was visualized by immunocytochemistry with primary antibody against TMV and secondary antibody conjugated with gold followed by silver enhancement. The sections were photographed under a light microscope. The labeling signal appears as white specks in cells in the dark-field image. A, Section from TMV-inoculated leaf; B, section from a mock-inoculated C. annuum leaf. Bar = 7.1 μm.

Accumulation of SHMV in a typical category V vein (defined in Fig. 1) from a mature inoculated leaf of N. benthamiana at 4 dpi. SHMV accumulation was visualized as described in Figure 3 using antibody against SHMV. A, Section from leaf tissue inoculated with SHMV. Virus was detected in three VP cells but not in C cells of this vein. B, Section from a mock-inoculated leaf tissue analyzed as for the vein in A. Bars = 12 μm.

Accumulation of SHMV in cells from a P. vulgaris leaf at 5 dpi. Accumulation of SHMV in cells was analyzed by immunocytochemistry using an antibody against SHMV and a goat anti-rabbit gold (20 nm) conjugate. Sections were examined and photographed under an electron microscope. A, Virion (V) aggregates labeled with immunogold in the cytoplasm of an infected mesophyll cell. Ch, Chloroplast; M, mitochondrion. Bar = 0.7 μm. B, Virion aggregates labeled with immunogold in the cytoplasm of a VP cell from a category V vein. No virion aggregates were detected in C cells of the vein. Inset, Magnification of several aggregates labeled with immunogold. S, SE; X, xylem TE. Bar = 2 μm.

Accumulation of SHMV in minor vein cells ofP. sativum. Accumulation of SHMV in cells was analyzed as described in Figure 6. A, Accumulation of SHMV in a category V vein from a mature inoculated leaf at 5 dpi. SHMV was detected in a BS cell, a VP cell, but not in the adjacent T cells. Bar = 1.5 μm. B, Accumulation of SHMV in a category VI vein from a systemically infected leaf at 8 dpi. Viral aggregates of SHMV were detected in both VP and T cells of the vein. Bar = 2 μm. Arrows point to magnified images of boxed areas showing immunogold labeling. S, SE; X, xylem TE.