Xylan reducing end sequence-containing oligosaccharides function as priming acceptors for Arabidopsis and Setaria...

Area of Science:

• Plant Biology
• Biochemistry
• Glycobiology

Background:

• Xylan, a major hemicellulose, has a conserved Reducing End Sequence (RES) in dicots and gymnosperms.
• The precise function of RES in xylan biosynthesis (primer or terminator) is unclear.

Purpose of the Study:

• To investigate if RES-containing oligosaccharides act as acceptor substrates for IRREGULAR XYLEM10 (IRX10) proteins.
• To compare the substrate preference of IRX10 from dicot (Arabidopsis thaliana) and grass (Setaria viridis).

Main Methods:

• In vitro enzymatic assays using fluorescently labeled oligosaccharides.
• Time-course analysis of product formation.
• Molecular docking simulations to predict binding interactions.

Main Results:

• Both Arabidopsis thaliana IRX10L and Setaria viridis IRX10 utilized RES-containing oligosaccharides (X-RES) as acceptor substrates.
• X-RES facilitated more efficient xylan elongation compared to linear oligosaccharides.
• Docking simulations indicated more stable binding of X-RES to the IRX10 active site.

Conclusions:

• A RES-containing oligosaccharide functions as an efficient primer in xylan biosynthesis in vitro.
• IRX10 exhibits flexibility in recognizing acceptor substrates.
• RES-primed elongation may be an ancestral trait in grasses.