The Localization of Cell Wall Components in the Whole-Mount Immunolabeled Nepenthes Digestive Glands

Glands from Nepenthes pitcher secrete various substances, including digestive enzymes, and absorb nutrients from digested prey. Due to the extreme specialization of these glands, they are an interesting model for studying secretory cells' structure and activity. This study aimed to fill the gap in the literature concerning the immunocytochemistry of Nepenthes digestive glands in the major cell wall polysaccharides and glycoproteins. To do this, the localization of the cell wall components in the cell walls of glandular cells was performed using whole-mount immunolabeled glands of Nepenthes albomarginata. Also, we wanted to check to what extent the cuticles of glandular cells with discontinuities would be a barrier to the antibodies. The technique used allowed for the localization of de-esterified pectic homogalacturonans in the outer walls of gland cells. The remaining antibodies (which detect esterified pectins, hemicelluloses, and arabinogalactan protein) marked only debris or secretion residues on the gland or epidermal surfaces. Positive labeling with LM19 and CCRC-M38 antibodies suggests the presence of pectic homogalacturonan in the very superficial part of the glands' cell walls, so they were easily accessible to antibodies.