Quantification of Protein Uptake by Endocytosis in Carnivorous Nepenthales

Abstract

Carnivorous plants adsorb prey-derived nutrients partly by endocytosis. This study quantifies endocytosis in Drosophyllum lusitanicum, Drosera capensis, Drosera roseana, Dionaea muscipula and Nepenthes × ventrata. Traps were exposed to 1% fluorescent-labeled albumin (FITC-BSA), and uptake was quantified repeatedly for 64 h. Formation of vesicles started after ≤1 h in adhesive traps, but only after 16 h in species with temporary stomach (D. muscipula and N. × ventrata). In general, there are similarities in the observed species, especially in the beginning stages of endocytosis. Nonetheless, further intracellular processing of endocytotic vesicles seems to be widely different between species. Endocytotic vesicle size increased significantly over time in all species except in D. capensis. Fluorescence intensity of the endocytotic vesicles increased in all species except D. muscipula. After 64 h, estimates for FITC-BSA absorption per gland ranged from 5.9 ± 6.3 ng in D. roseana to 47.8 ± 44.3 ng in N. × ventrata, demonstrating that endocytosis substantially contributes to the adsorption of prey-derived nutrients.

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

“…Carnivorous plants have glands with permeable cuticles because of the occurrence of cuticular discontinuities that allow secretion and endocytosis to occur [4]. In some carnivorous plants, endocytosis has been confirmed as one way that they absorb the nutrients from the bodies of captured prey [31][32][33]. There are several types of these discontinuities [4,[34][35][36][37].…”

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

“…He suggested that the subcellular mechanisms of hydrolase synthesis and secretion in carnivorous plant glands (in Drosophyllum as well as in the various species of Droseraceae) are analogous to the two subcellular strategies characteristic of the animal pancreas. Concerning uptake of extracellular substances, endocytosis was observed in the glands of D. lusitanicum [28,29]. Interestingly, endocytosis occurs not only in digestive glands assumed to be responsible for nutrition, but also in mucilage glands.…”

“…They are supplied with an appropriate glandular apparatus that can lure [20][21][22][23][24] and capture prey, e.g., fly-paper (adhesive) traps [25] and the pitchers of some Nepenthes with viscous pitcher fluid [26,27]. Nutrients from captured prey are absorbed by these digestive and absorptive organs [1, 20,28,29] analogous to the stomach and intestine of animals [30]. The glandular apparatus of carnivorous plant traps (in Nepenthales and Lentibulariaceae) contains transfer cells [1, 20,31,32].…”