The Localization of Cell Wall Components in the Quadrifids of Whole-Mount Immunolabeled Utricularia dichotoma Traps

Abstract

Utricularia (bladderworts) are carnivorous plants. They produce small hollow vesicles, which function as suction traps that work underwater and capture fine organisms. Inside the traps, there are numerous glandular trichomes (quadrifids), which take part in the secretion of digestive enzymes, the resorption of released nutrients, and likely the pumping out of water. Due to the extreme specialization of quadrifids, they are an interesting model for studying the cell walls. This aim of the study was to fill in the gap in the literature concerning the immunocytochemistry of quadrifids in the major cell wall polysaccharides and glycoproteins. To do this, the localization of the cell wall components in the quadrifids was performed using whole-mount immunolabeled Utricularia traps. It was observed that only parts (arms) of the terminal cells had enough discontinuous cuticle to be permeable to antibodies. There were different patterns of the cell wall components in the arms of the terminal cells of the quadrifids. The cell walls of the arms were especially rich in low-methyl-esterified homogalacturonan. Moreover, various arabinogalactan proteins also occurred. Cell walls in glandular cells of quadrifids were rich in low-methyl-esterified homogalacturonan; in contrast, in the aquatic carnivorous plant Aldrovanda vesiculosa, cell walls in the glandular cells of digestive glands were poor in low-methyl-esterified homogalacturonan. Arabinogalactan proteins were found in the cell walls of trap gland cells in all studied carnivorous plants: Utricularia, and members of Droseraceae and Drosophyllaceae.

Do Arabinogalactan Proteins Occur in the Transfer Cells of Utricularia dichotoma?

“…When whole quadrifids were analyzed (without sectioning), it was only possible to detect AGPs in the arms [ 29 ]. We proposed that this was connected to the cuticle structure and the availability of cell wall components for antibodies.…”

“…AGPs were recorded in the wall labyrinth in transfer cells of various species (e.g., [ 25 , 26 , 27 , 28 ]). Płachno and Kapusta [ 29 ] localized the AGPs in quadrifids using whole-mount immunolabeled Utricularia traps. However, immunolabeling was only successful in the cell walls of parts of quadrifid arms, where the cuticle has an open structure.…”

Do Cuticular Gaps Make It Possible to Study the Composition of the Cell Walls in the Glands of Drosophyllum lusitanicum?

“…In addition, as we also showed, such material reacts with some of the antibodies, which may be due to the fact that it is partly derived from the plant's secretions. In the trichomes from Utricularia dichotoma traps, Płachno and Kapusta [65] showed that the success of the labeling was connected to the permeability of the cuticle (the occurrence of discontinuities). In the case of Drosophyllum, some of the results are ambiguous, and it is sometimes difficult to distinguish whether the signal came from the peripheral part of the wall or from the secretion or the material on the cell surface.…”

“…Knowing the occurrence of wall components in the sliced material where the walls are accessible to antibodies, we compared them with the whole-mount immunolabeling method, which was mainly used for root hairs and pollen tubes [60][61][62][63][64]. Recently, we used this method in another carnivorous plant in order to localize the cell wall components in the trichomes from Utricularia dichotoma traps [65]; however, we had only partial success as the labeling was limited to the glandular cell fragments in which the cuticle was discontinuous.…”

Cell Wall Microdomains in the External Glands of Utricularia dichotoma Traps

“…Our main aim of this study is to check if different cell wall layers have a different composition. Also, it will be interesting to see if arabinogalactan proteins (AGPs) are found in highly specialized terminal cells, especially since AGPs are localized in quadrifids of Utricularia [ 47 ], which produce digestive enzymes, absorb nutrients from prey digestion, but they probably also participate in pumping out water from the trap [ 40 , 43 , 48 , 49 ].…”