Differences in the Occurrence of Cell Wall Components between Distinct Cell Types in Glands of Drosophyllum lusitanicum

Abstract

Carnivorous plants are mixotrophs that have developed the ability to lure, trap, and digest small organisms and utilize components of the digested bodies. Leaves of Drosophyllum lusitanicum have two kinds of glands (emergences): stalked mucilage glands and sessile digestive glands. The stalked mucilage glands perform the primary role in prey lure and trapping. Apart from their role in carnivory, they absorb water condensed from oceanic fog; thus, plants can survive in arid conditions. To better understand the function of carnivorous plant emergences, the molecular composition of their cell walls was investigated using immunocytochemical methods. In this research, Drosophyllum lusitanicum was used as a study system to determine whether cell wall immunocytochemistry differs between the mucilage and digestive glands of other carnivorous plant species. Light and electron microscopy were used to observe gland structure. Fluorescence microscopy revealed the localization of carbohydrate epitopes associated with the major cell wall polysaccharides and glycoproteins. The mucilage gland (emergence) consists of a glandular head, a connecting neck zone, and stalk. The gland head is formed by an outer and inner layer of glandular (secretory) cells and supported by a layer of endodermoid (barrier) cells. The endodermoid cells have contact with a core of spongy tracheids with spiral-shaped thickenings. Lateral tracheids are surrounded by epidermal and parenchymal neck cells. Different patterns of cell wall components were found in the various cell types of the glands. Cell walls of glandular cells generally are poor in both low and highly esterified homogalacturonans (HGs) but enriched with hemicelluloses. Cell walls of inner glandular cells are especially rich in arabinogalactan proteins (AGPs). The cell wall ingrowths in glandular cells are significantly enriched with hemicelluloses and AGPs. In the case of cell wall components, the glandular cells of Drosophyllum lusitanicum mucilage glands are similar to the glandular cells of the digestive glands of Aldrovanda vesiculosa and Dionaea muscipula.

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

“…For the above reasons, the presence of AGPs in the cell wall of the secretory cells of the quadrifids is not surprising, especially since these cells are responsible for the secretion of enzymes and subsequent nutrient intake, and these processes involve vesicle trafficking and membrane recycling, in which AGPs participate [ 70 , 71 , 72 ]. Moreover, the cell walls of the secretory cells in the glands of other carnivorous plants such as Drosophyllum [ 38 ], Dionaea [ 34 , 35 ] and Aldrovanda [ 36 , 37 ] are enriched with arabinogalactan proteins. We found that the cell walls of the arms are especially rich in low-methyl-esterified homogalacturonans.…”

“…However, to prove this, it would be necessary to study a mutant of Utricularia with a disruption of pectin production. However, in the glands of carnivorous plants from the families Droseraceae and Drosophyllaceae that have been studied to date, the cell walls of secretory cells have been poor in low-methyl-esterified homogalacturonans (as detected by the JIM5 and LM19 antibodies) [ 34 , 35 , 38 ]. One can only speculate about whether these differences are related to the phylogenetic position of the species or to the functioning of the glands.…”

“…To remove the HG from the cell walls, the traps were pretreated with 0.1 M sodium carbonate pH = 11.4 for 2 h at room temperature. This was followed by digestion with a pectate lyase 10 A (Nzytech) at 10 μg/mL for 2 h at room temperature in 50 mM N-cyclohexyl-3-aminopropane sulfonic acid (CAPS) with the addition of 2 mM of a CaCl 2 buffer at pH 10 [ 38 ], and then incubation with the JIM5, JIM7, LM15, and LM25 antibodies, as described above.…”

“…For the scanning electron microscopy (SEM), the traps were fixed in methanol and later transferred to ethanol, and then transferred to acetone and dried using supercritical CO 2 . The material was then sputter-coated with gold and examined at an accelerating voltage of 20 kV using a Hitachi S-4700 scanning electron microscope (Tokyo, Japan), which is housed at the Institute of Geological Sciences, Jagiellonian University, Kraków, Poland [ 38 ].…”

“…Due to the extreme specialization of the quadrifids, they are an interesting model to use to study cell walls. Recently, in a series of works, we showed the major cell wall polysaccharides and glycoproteins in the various glands of carnivorous plants; however, our studies were limited to Aldrovanda vesiculosa [ 34 , 35 ], Dionaea muscipula [ 36 , 37 ], and Drosophyllum lusitanicum [ 38 ]. This aim of this study is to fill in the gap in the literature concerning the immunocytochemistry of the quadrifids in the major cell wall polysaccharides and glycoproteins.…”