Fructans are polyfructose molecules produced by approximately 15% of the flowering plant species. It is possible that, in addition to being a storage carbohydrate, fructans have other physiological roles. Owing to their solubility they may help plants survive periods of osmotic stress induced by drought or cold. To investigate the possible functional significance of fructans, use was made of transgenic tobacco (Nicotiana tabacum) plants that accumulate bacterial fructans and hence possess an extra sink for carbohydrate. Biomass production was analyzed during drought stress with the use of lines differing only in the presence of fructans. Fructan-producing tobacco plants performed significantly better under polyethyleneglycol-mediated drought stress than wild-type tobacco. l h e growth rate of the transgenic plants was significantly higher (+55"/0), as were fresh weight (+33%) and dry weight (+59%) yields. l h e difference in weight was observed in ai1 organs and was particularly pronounced in roots. Under unstressed control conditions the presente of fructans had no significant effect on growth rate and yield.Under all conditions the total nonstructural carbohydrate content was higher in the transgenic plants. We conclude that the introduction of fructans in this non-fructan-producing species mediates enhanced resistance to drought stress. plant fructans varies from 10 to 200 Fru units. Differences in fructan length not only result from taxonomic variation but are also subject to environmental influences: plants have been reported to respond to changing conditions by shifting the average length of their fructan pool (Pontis and De1 Campillo, 1985).In addition to plants, severa1 bacteria synthesize fructans. Bacterial fructan biosynthesis from Suc involves only one enzyme. Most bacterial fructans have a very high DP (up to 100,000) and a 2-6-linkage type with occasional2-1 branching (Dedonder, 1966).One of the goals of our studies is to elucidate why some plant taxa use fructans as the predominant storage carbohydrate instead of starch, which is ubiquitous in the plant kingdom. In other words, what is the functional significance of fructans and under which selection pressure has fructan metabolism evolved? The most obvious differences between starch and fructan are the location and solubility. Fructans are located in the vacuole and are soluble, in contrast to the insoluble plastidic starch. A possible advantage of vacuoles as storage organelles could be that the storage capacity of vacuoles may be larger than that of the plastids, since the vacuole constitutes 95% of the protoplast volume. Fructan storage capacity in plants may be further (onion, tulip), tubers (Jerusalem artichoke), or succulent stems ( A~~~~) .Fructan is indeed often accumulated to higher quantities than starch (Brocklebank and Hendry, 1989).Since fructans are soluble, they may play a role in the osmotic adjustment of natural fructan accumulators to changing environmental conditions via variation in the DP of the fructan pool. An of osmotic a...
In the present study we used flow cytometry to investigate the phagocytosis of fluorescein isothiocyanate-labeled herpes simplex virus type 1 (FITC-HSV-1) by rat alveolar macrophages and the effects of surfactant protein A (SP-A) on this process. The phagocytosis of FITC-HSV-1 by alveolar macrophages, which was studied as a model for virus phagocytosis in general, was strongly enhanced in the presence of SP-A. The SP-A-mediated phagocytosis was time and concentration dependent, reaching a maximal level after 15 min of incubation and at an SP-A concentration of 5 micrograms/ml. Using a fluorescence quenching technique, we could show that at least 65% of the viruses were indeed internalized by the macrophages. The addition of SP-A to the system was sufficient for the phagocytosis of FITC-HSV-1 by the alveolar macrophages, suggesting that SP-A acts as an opsonin. This hypothesis was further strengthened by the observation that F(ab')2 fragments of immunoglobulin G directed against SP-A could abolish FITC-HSV-1 phagocytosis by alveolar macrophages preincubated with SP-A. Comparing the opsonic capacity of serum and SP-A, SP-A proved to be twice as potent as serum in stimulating phagocytosis of FITC-HSV-1 by alveolar macrophages. Complement factor C1q, which is known to possess a similar collagen-like domain as SP-A, did not stimulate phagocytosis of FITC-HSV-1 by alveolar macrophages nor did it inhibit SP-A-mediated HSV-1 phagocytosis. This study demonstrates that SP-A may play an important role in the antiviral defenses of the lung.
Abstract-Intrusive growth is a type of cell elongation when the rate of its longitudinal growth is higher than that of surrounding cells; therefore, these cells intrude between the neighboring cells penetrating the middle lamella. The review considers the classical example of intrusive growth, e.g., elongation of sclerenchyma fibers when the cells achieve the length of several centimeters. We sum the published results of investigations of plant fiber intrusive growth and present some features of intrusive growth characterized by the authors for flax (Linum usitatissimum L.) and hemp (Cannabis sativa L.) fibers. The following characteristics of intrusive growth are considered: its rate and duration, relationship with the growth rate of surrounding cells, the type of cell elongation, peculiarities of the fiber primary cell wall structure, fibers as multinucleate cells, and also the control of intrusive growth. Genes, which expression is sharply reduced at suppression of intrusive growth, are also considered. Arguments for separation of cell elongation and secondary cell wall formation in phloem fibers and also data indicating diffuse type of cell enlargement during intrusive growth are presented.
Bacterial fructans with a high degree of polymerisation cause a very large increase in surface pressure of lipid monolayers at the air-water interface with a broad range of lipids, including phosphatidylethanolamine and several types of phosphatidylcholines. The surface active effect of fructans contrasts strongly with the maximal effects observed for trehalose, sucrose and glucose under comparable conditions (20 and 0.6 mN/m for fructans and the other sugars, respectively). The results demonstrate a profound and specific membrane interaction of the fructans which is probably very different from the effect of the smaller carbohydrates. The fructan concentrations used in this study are within the physiological range observed in fructan-accumulating plants. The suggested water-stress protective effect of fructans may be induced by membrane-fructan interaction which prevent lipid condensation and phase transitions to take place.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.
hi@scite.ai
10624 S. Eastern Ave., Ste. A-614
Henderson, NV 89052, USA
Copyright © 2024 scite LLC. All rights reserved.
Made with 💙 for researchers
Part of the Research Solutions Family.