Figure 5. The secretory pathway is strongly activated in nodule zones II and III.
(A) Distribution of genes exhibiting expression profiles 5–8 (321 genes) and the total probe-set (2366 genes) into categories of the secretory pathway. A significant enrichment or depletion of categories, supported by Fisher's exact test, is indicated by an asterisk (*). The p-values are 10−42 for the category “non-secretory proteins”, 10−52 for the category “secretory proteins” and 10−42 for the category “protein secretion” (combined categories “membrane proteins”, “secretory system” and “secretory proteins”). (B) In situ hybridization with an antisense probe of the SPP gene. The position of nodule zones I, II and III are indicated. SPP expression is observed as a black signal in the proximal zone II. The inset shows a control hybridization with a sense probe. (C–E) Immunolocalization of the ER specific KDEL marker MAC 256. On the left are the DIC images and on the right are the fluorescence images. (D) is a magnification of the region outlined in (C). (E) is an enlargement of the region outlined in (D). Scale bars are 100 µm (B,C), 20 µm (D) and 10 µm (E).