Raffinose family oligosaccharides (RFOs) is the generic term used for oligosaccharides which are synthesised by sucrose and galactosyl through (α-1,6) glycosidic bonding and which polymerization degree is less than 15 monosaccharides molecular. The first committed step in the biosynthetic pathway of RFOs is that Galactinol synthase (GolS) catalyzes the reaction of uridine diphosphate (UDP) -α-D- long, synthesized from sucrose and galactose + myoinositol → UDP + galactinol. Galactinol is the unique galactosyl donor for RFOs synthesis in plants (Keller & Pharr, 1996; Peterbauer et al, 2002). GolS is a key regulatory gene in RFOs synthesis (Keller & Pharr, 1996).
As non-structural carbohydrates,precursors that are joined by an (α-1,6) glycosidic bond. RFOs are the second largest group of sugars present in plant tissues (French, 1954), they and are non-structural carbohydrates that play essential roles in plant growth and development. Firstly, RFOs’ in the following three ways. First, theaccumulation of RFOs can be induced by stresses such as drought, cold, and salt stresses and so on. Accordingly, research shows that RFOs are a very important material in plants for resisting abiotic stressresistance in plants (Bachmann et al, 1994; Haritatos et al, 1996; Taji et al, 2002; Pennycooke et al, 2003; Peters, 2007; dos Santos et al, 2011). Secondly, Second, RFOs can act as transport sugars in some plants, RFOs participate by participating in the phloem loading which of phloem. This is the initial step in photoassimilate export. Sucrose, where sucrose diffuses from bundle sheath cells into intermediary cells through the plasmodesmata and is converted into RFOs. Because As RFOs are bigger in size larger than sucrose and exceed the size exclusion limit of the plasmodesmata, they can’t move back cannot return to the bundle sheath cells. This process creates, thus creating a sucrose concentration gradient and driving force for mass flow. This, in a mechanism is known as the polymer trap model (Turgeon, 1996; Turgeon & Medville, 2004). In addition,Third, as RFOs are the main storage form of carbohydrates in the seeds of many speciesseeds, they not only provide energy for seed germination, but they are also necessary for maintaining the structure of cells under desiccation (Horbowicz & Obendorf, 1994; Black et al, 1996; Obendorf, 1997; Brenac et al, 1997; Hoekstra et al, 1997; Bentsink et al, 2000), positive correlation between). Thus the content of RFOs and has been observed to positively correlate with the storage period of seeds has been observed(Horbowicz & Obendorf, 1994; Lin & Huang, 1994; Li et al, 2011).
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