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OLIgo Mass Profiling (OLIMP) of Extracellular Polysaccharides
Published on: June 20, 2010
Identification of mono-, oligo-, and polysaccharides secreted from soybean roots
Paul Benjamin Timotiwu1, Naoki Sakurai
1Faculty of Integrated Arts and Sciences, Hiroshima University, Higashi-Hiroshima 739-8521, Japan.
Abstract:
The mist culture system was conducted to study secreted polysaccharides from soybean ( Glycine max) roots grown for 15 days. Roots were rinsed with distilled water (DW) for 15 min, then with 30 mM oxalic acid (OXA) for 15 min to remove ionically bound sugar. Released sugars were further fractionated into low (L) and high (H) molecular weight fractions with Sephadex G-10. DW rinsing released 190 microg neutral sugar (NS) and 62 microg uronic acid (UA) per plant, while 374 microg NS and 70 microg UA per plant were released by OXA rinsing. Acetylation analysis revealed that the L fraction by DW and OXA mainly consisted of glucose (Glc), pinitol, and UA, whereas the H fraction mainly consisted of arabinose (Ara), galactose (Gal), Glc, and UA. The presence of rhamnose (2%-6%) in both fractions suggests secretion of rhamnogalacturonans. Methylation analysis revealed that the H fraction by DW and OXA contained T-Ara, 3-, 6-, and 3,6-Gal, suggesting the presence of type II arabinogalactan and arabinogalactan proteins. HPLC analysis detected mono-, di-, and tri-GalA in the L fraction by DW and OXA. Substances corresponding to sucrose, kojibiose, cello- and laminari-oligosaccharides were also found in root exudates.
Insights
Soybean roots secrete complex sugars, including glucose and arabinose, which are released using distilled water and oxalic acid treatments. These findings reveal the composition of root exudates and potential rhamnogalacturonans.
Area of Science:
- Plant Biology
- Biochemistry
- Molecular Biology
Background:
- Soybean (Glycine max) root exudates play a crucial role in plant-soil interactions.
- Understanding the composition of secreted polysaccharides is vital for elucidating root function and plant health.
Purpose of the Study:
- To investigate the types and molecular weights of polysaccharides secreted by soybean roots.
- To characterize the sugar composition of root exudates using different extraction methods.
Main Methods:
- Mist culture system for growing soybean roots.
- Sequential rinsing with distilled water and oxalic acid to extract root exudates.
- Sephadex G-10 chromatography for fractionating polysaccharides by molecular weight.
- Acetylation, methylation, and High-Performance Liquid Chromatography (HPLC) analyses for sugar identification.
Main Results:
- Oxalic acid rinsing released significantly more neutral sugar and uronic acid than distilled water.
- Low molecular weight fractions contained glucose, pinitol, and uronic acid.
- High molecular weight fractions were rich in arabinose, galactose, glucose, and uronic acid, indicating rhamnogalacturonans and type II arabinogalactans.
- HPLC detected various galacturonic acid oligosaccharides and other sugars like sucrose and kojibiose in root exudates.
Conclusions:
- Soybean roots secrete a diverse range of polysaccharides, including rhamnogalacturonans and arabinogalactan proteins.
- The extraction method influences the yield and composition of detected root exudates.
- The identified sugars suggest complex roles in root development, nutrient uptake, or defense mechanisms.
