Figure 2.

PUB1 expression is associated with all stages of symbiotic AM fungal infection. Transgenic lines expressing ProPUB1-GUS were analyzed in response to R. irregularis. Roots were stained for GUS activity (in magenta) and fungus was visualized by ink coloration (in blue). A and B, Noninoculated root systems of 2 (A) and 5 weeks (B). C and D, Inoculated root systems of 2 (C) and 5 wpi (D). White rectangles in (A) and (C) indicate the zone shown on the right of the panel on a white background to highlight the magenta GUS staining. E, GUS-stained areas are associated with the presence of the fungus (dark blue). F, G, Magnification (F) and transversal section (G) of the penetration zone showed expression of PUB1 in the epidermal cell directly in contact with a hyphopodium and in a few outer cortical cells in the immediate vicinity (arrows and arrowheads indicate the GUS staining and the fungus, respectively). H, I, Expression of PUB1 was detected in the cortex under the infection site in cortical cells directly associated with propagating internal hyphae or in cortical cells in the vicinity of the hyphae, but not necessarily in immediate contact. J, Magnification of a transversal section showing ProPUB1-GUS expression in cells containing arbuscules (arrowheads) and in adjacent cells without arbuscule.