Fructans and raffinose family oligosaccharides (RFOs) are the two most important classes of water-soluble carbohydrates in plants. Recent progress is summarized on their metabolism (and regulation) ...and on their functions in plants and in food (prebiotics, antioxidants). Interest has shifted from the classic inulin-type fructans to more complex fructans. Similarly, alternative RFOs were discovered next to the classic RFOs. Considerable progress has been made in the understanding of structure-function relationships among different kinds of plant fructan metabolizing enzymes. This helps to understand their evolution from (invertase) ancestors, and the evolution and role of so-called "defective invertases." Both fructans and RFOs can act as reserve carbohydrates, membrane stabilizers and stress tolerance mediators. Fructan metabolism can also play a role in osmoregulation (e.g., flower opening) and source-sink relationships. Here, two novel emerging roles are highlighted. First, fructans and RFOs may contribute to overall cellular reactive oxygen species (ROS) homeostasis by specific ROS scavenging processes in the vicinity of organellar membranes (e.g., vacuole, chloroplasts). Second, it is hypothesized that small fructans and RFOs act as phloem-mobile signaling compounds under stress. It is speculated that such underlying antioxidant and oligosaccharide signaling mechanisms contribute to disease prevention in plants as well as in animals and in humans.
Plant vacuoles are unique, multifunctional organelles among eukaryotes. Considerable new insights in plant vacuolar protein sorting have been obtained recently. The basic machinery of protein export ...from the endoplasmic reticulum to the Golgi and the classical route to the lytic vacuole and the protein storage vacuole shows many similarities to vacuolar/lysosomal sorting in other eukaryotes. However, as a result of its unique functions in plant defence and as a storage compartment, some plant‐specific entities and sorting determinants appear to exist. The alternative post‐Golgi route, as found in animals and yeast, probably exists in plants as well. Likely, adaptor protein complex 3 fulfils a central role in this route. A Golgi‐independent route involving plant‐specific endoplasmic reticulum bodies appears to provide sedentary organisms such as plants with extra flexibility to cope with changing environmental conditions.
Plant vacuoles are unique, multifunctional organelles among eukaryotes. This review summarizes the new insights in plant vacuolar protein sorting pathways. Although these pathways greatly resemble those observed in animals, some plant‐specific entities exist. A unique Golgi‐independent route provides plants, as sedentary organisms, with extra flexibility to cope with ever changing environmental conditions
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Sugars do not only act as source of energy, but they also act as signals in plants. This mini review summarizes the emerging links between sucrose-mediated signaling and the cellular networks ...involved in flowering time control and defense. Cross-talks with gibberellin and jasmonate signaling pathways are highlighted. The circadian clock fulfills a crucial role at the heart of cellular networks and the bilateral relation between sugar signaling and the clock is discussed. It is proposed that important factors controlling plant growth (DELLAs, PHYTOCHROME INTERACTING FACTORS, invertases, and trehalose-6-phosphate) might fulfill central roles in the transition to flowering as well. The emerging concept of "sweet immunity," modulated by the clock, might at least partly rely on a sucrose-specific signaling pathway that needs further exploration.
An improved method for the measurement of fructans in wheat grains is presented. A mild acid treatment is used for fructan hydrolysis, followed by analysis of the released glucose and fructose with ...high performance anion exchange chromatography with pulsed amperometric detection (HPAEC-PAD). Not only the amount of fructose set free from fructans but also the released glucose can be quantified accurately, allowing determination of the average degree of polymerization of fructans (DPav). Application of the mild acid treatment to different grain samples demonstrated that a correction should be made for the presence of sucrose and raffinose, but not for stachyose or higher raffinose oligosaccharides. The fructan content and DPav of spelt flour, wheat flour, and whole wheat flour were 0.6%, 1.2%, and 1.8% of the total weight and 4, 5, and 6, respectively. Validation experiments demonstrate that the proposed quantification method is accurate and repeatable and that also the DPav determination is precise.
Fructans of the saline world Kırtel, Onur; Versluys, Maxime; Van den Ende, Wim ...
Biotechnology advances,
09/2018, Volume:
36, Issue:
5
Journal Article
Peer reviewed
Open access
Saline and hypersaline environments make up the largest ecosystem on earth and the organisms living in such water-restricted environments have developed unique ways to cope with high salinity. As ...such these organisms not only carry significant industrial potential in a world where freshwater supplies are rapidly diminishing, but they also shed light upon the origins and extremes of life. One largely overlooked and potentially important feature of many salt-loving organisms is their ability to produce fructans, fructose polymers widely found in various mesophilic Eubacteria and plants, with potential functions as storage carbohydrates, aiding stress tolerance, and acting as virulence factors or signaling molecules. Intriguingly, within the whole archaeal domain of life, Archaea possessing putative fructan biosynthetic enzymes were found to belong to the extremely halophilic class of Halobacteria only, indicating a strong, yet unexplored link between the fructan syndrome and salinity. In fact, this link may indeed lead to novel strategies in fighting the global salinization problem. Hence this review explores the unknown world of fructanogenic salt-loving organisms, where water scarcity is the main stress factor for life. Within this scope, prokaryotes and plants of the saline world are discussed in detail, with special emphasis on their salt adaptation mechanisms, the potential roles of fructans and fructosyltransferase enzymes in adaptation and survival as well as future aspects for all fructanogenic salt-loving domains of life.
In plant tissues, sugar levels are determined by the balance between sugar import, export, and sugar synthesis. So far, water soluble carbohydrate (WSC) dynamics have not been investigated in a ...diurnal context in wheat stems as compared to the dynamics in flag leaves during the terminal phases of grain filling. Here, we filled this research gap and tested the hypothesis that WSC dynamics interlink with gene expression of
The main stems and flag leaves of two genotypes, Westonia and Kauz, were sampled at four hourly intervals over a 24 h period at six developmental stages from heading to 28 DAA (days after anthesis). The total levels of WSC and WSC components were measured, and
gene expression was quantified at 21 DAA. On average, the total WSC and fructan levels in the stems were double those in the flag leaves. In both cultivars, diurnal patterns in the total WSC and sucrose were detected in leaves across all developmental stages, but not for the fructans 6-kestose and bifurcose. However, in stems, diurnal patterns of the total WSC and fructan were only found at anthesis in Kauz. The different levels of WSC and WSC components between Westonia and Kauz are likely associated with leaf chlorophyll levels and fructan degradation, especially 6-kestose degradation. High correlation between levels of
expression and sucrose in leaves indicated that
expression is likely to be influenced by the level of sucrose in leaves, and the combination of high levels of
expression and sucrose in Kauz may contribute to its high grain yield under well-watered conditions.
Plants suffering from abiotic stress are commonly facing an enhanced accumulation of reactive oxygen species (ROS) with damaging as well as signalling effects at organellar and cellular levels. The ...outcome of an environmental challenge highly depends on the delicate balance between ROS production and scavenging by both enzymatic and metabolic antioxidants. However, this traditional classification is in need of renewal and reform, as it is becoming increasingly clear that soluble sugars such as disaccharides, raffinose family oligosaccharides and fructans – next to their associated metabolic enzymes – are strongly related to stress‐induced ROS accumulation in plants. Therefore, this review aims at extending the current concept of antioxidants functioning during abiotic stress, with special focus on the emanate role of sugars as true ROS scavengers. Examples are given based on their cellular location, as different organelles seem to exploit distinct mechanisms. Moreover, the vacuole comes into the picture as important player in the ROS signalling network of plants. Elucidating the interplay between the mechanisms controlling ROS signalling during abiotic stress will facilitate the development of strategies to enhance crop tolerance to stressful environmental conditions.
In this review, emphasis is paid to (1) the emerging role of sugars (and derivatives) as antioxidants and (2) the role of organelles, with special attention for the vacuole in the cellular redox network.
The inulin-type fructans in Jerusalem artichoke (
L.) tubers exhibit different degrees of polymerization and are critical for germination. We aimed to characterize the sugar metabolism dynamics in ...the tubers without bud eyes or shoots (T) and BE/S of indoor- and field-grown Jerusalem artichokes during germination.
and
(1-fructan exohydrolases II and III, inulin-degrading enzymes) expression increased 5 days after planting indoors, whereas
expression increased 72 days after planting in the field in T and BE/S.
(sucrose:sucrose 1-fructosyl transferase, inulin synthesis initiator), and
(fructan:fructan 1-fructosyl transferase, inulin elongator) expression generally decreased in indoor-grown T. The enzyme activities of 1-FEH and 1-FFT were unchanged during germination in both indoor- and field-grown T and BE/S, whereas 1-SST activity decreased in indoor-grown T, while 1-FEH and 1-FFT activities increased as a function of germination time in BE/S of both indoor- and field-grown tubers. The total soluble sugar content gradually decreased in T after germination indoors or in the field, while at the end of germination, the sucrose and fructan contents decreased, and fructose content increased in the field. The enzyme activities of soluble vacuolar (VI) or neutral invertase (NI) did not change significantly, except at the late germination stage. Sucrose synthase (SS) and sucrose-phosphate synthase (SPS) activities were not significantly changed in T and BE/S in indoor-grown artichokes, while SS activity gradually increased, and SPS activity gradually decreased in field-grown artichokes, alongside sucrose degradation. Compared to T, BE/S generally had higher enzyme activities of 1-FEH and 1-FFT, promoting inulin hydrolysis. This work shows that the process of tuber germination is similar indoors and in the field, and germination studies can therefore be conducted in either environment.
Fructans are multifunctional fructose‐based water soluble carbohydrates found in all biological kingdoms but not in animals. Most research has focused on plant and microbial fructans and has received ...a growing interest because of their practical applications. Nevertheless, the origin of fructan production, the so‐called “fructan syndrome,” is still unknown. Why fructans only occur in a limited number of plant and microbial species remains unclear. In this review, we provide an overview of plant and microbial fructan research with a focus on fructans as an adaptation to the environment and their role in (a)biotic stress tolerance. The taxonomical and biogeographical distribution of fructans in both kingdoms is discussed and linked (where possible) to environmental factors. Overall, the fructan syndrome may be related to water scarcity and differences in physicochemical properties, for instance, water retaining characteristics, at least partially explain why different fructan types with different branching levels are found in different species. Although a close correlation between environmental stresses and fructan production is quite clear in plants, this link seems to be missing in microbes. We hypothesize that this can be at least partially explained by differential evolutionary timeframes for plants and microbes, combined with potential redundancy effects.
The capacity to biosynthesize fructans, fructose‐based oligo and polysaccharides, is scattered over certain plant and microbial families. This review represents the first attempt to grasp the overall meaning of the “fructan syndrome”, crossing plants and microbes. By highlighting functional similarities and differences, this review prepares the ground for further research in plants and microbes, with focus on water scarcity and fructan signalling as common themes.
•Inulin-type fructans may act as signals that are sensed by Toll Like Receptors•Immunomodulatory effects depend on the DP and type of fructans•Immunomodulatory effects may be different in different ...cell types•Fructans are food ingredients with prebiotic and immunomodulatory properties
Fructans are natural fructose polymers that are used for their prebiotic and health improving properties in functional foods. Although the immunomodulatory effects of fructans on animal cells are known, their mode of action has only recently been unraveled. It was found that inulin-type fructans act as signals in animals, stimulating immune cell activity through Toll Like Receptor (TLR)° mediated signaling. This review summarizes recent progress in the area with focus on possible fructan signaling and downstream signaling events. Intriguingly, synergistic effects with phenolic compounds are often observed. Fructans and their fermentation products (short chain fatty acids and hydrogen gas) lead to a more reduced cellular status and a modulation of the immune system, aiming at disease prevention. Moreover, evidence is accumulating that fructans may alleviate inflammatory symptoms in diseased subjects. In conclusion, fructans are of interest in functional foods because of their prebiotic, antioxidant and immunomodulatory properties.
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