Fig. 4. Low-esterified homogalacturonan distribution is affected in gnom¹⁸⁴ and negatively correlates with sites of LR inception.

(A) Immunohistochemical quantification of cell wall area per root cross-section area with the antibody against de-esterified and Ca²⁺ cross-linked homogalacturonan 2F4 (P_2F4 = 0.31, Wilcoxon rank sum test), de-esterified homogalacturonan LM19 (P_LM19 = 0.0028, t test), and esterified homogalacturonan LM20 (P_LM20 = 0.042, t test). False discovery rate method adjustment was applied. (B and C) Transmission electron microscopy (TEM) images of LM19 immunogold localization. De-esterified homogalacturonan is marked by round black gold particles. Cell types (end, endodermis; per, pericycle) are indicated in the cytoplasmic region of each cell. Insets show the three-way dense (B) and particle-free (C) junctions. Note the collapsed and antibody-free endodermis-endodermis cell wall marked by the arrowhead. (D) Quantification of gold particles in pericycle-endodermis junctions; genotypes show different particle densities (P = 0.001, Wilcoxon test). (E and F) Immunohistochemistry with LM19 (E) and LM20 (F) antibodies of root cross-sections in regions of emerging LRP. White arrowheads indicate the side facing LRP; blue arrowheads indicate the opposite (control) side. Scale bar, 20 μm. (G and H) Quantification and statistics of (E) and (F), respectively. Wilcoxon paired test statistics are given above boxes.