Rhamnogalacturonan I Forms a Gel with Hyperelastic Properties
Rhamnogalacturonans I are complex pectin polysaccharides that are extremely variable in structure and properties and widely represented in various sources. The complexity and diversity of structure of rhamnogalacturonans I limit information about the properties and supramolecular organization of these polysaccharides, including the relationship between these parameters and the functions of rhamnogalacturonans I in plant cells. This report on the example of rhamnogalacturonan I from flax gelatinous fibers describes for the first time the capacity of this type of pectic polysaccharides to form hydrogels with hyperelastic properties at physiological concentrations. According to IR-spectroscopy, the water molecules are more tightly retained in the gelling rhamnogalacturonan I from flax fiber cell wall in comparison with the non-gel-forming rhamnogalacturonan I from primary cell wall of potato. With increasing strength of water binding by rhamnogalacturonan I, there is an increase of elastic modulus and decrease of Poisson's ratio of gel formed by this polysaccharide. A model of hyperelastic rhamnogalacturonan I capture by interacting cellulose microfibrils, constructed using the finite element method, confirmed the suitability of the rhamnogalacturonan I gel with established properties for the function in the gelatinous cell wall. This allows us to consider this tissue- and stage-specific pectic polysaccharide as an important factor in the creation of gelatinous fiber contractility.