Figure 4. Detection of polygalacturonase mRNA in adult rice weevil digestive tracts by in situ hybridization. Paraformaldehyde-fixed digestive tracts were treated with a digoxigenin (DIG)-labeled RNA probe followed by incubation with an anti-DIG antibody (top panel); with hybridization solution lacking the RNA probe followed by incubation with the anti-DIG antibody (middle panel); or with the DIG-labeled RNA probe but not with the anti-DIG antibody (bottom panel). The middle and bottom panels, then, are controls for the top panel. The guts were photographed under a compound microscope using brightfield illumination. Arrows indicate the finger-like caecae. C, crop; PV, periventriculus; AMG, anterior midgut.