Local distribution of polysaccharides in Sugarcane culms using MALDI-image

Understanding the composition and architecture of the vegetal cell wall is important for both understanding function, development and intrinsic composition of plant tissues and for designing the best enzymatic approaches for efficient hydrolysis and posterior biotechnological industrial uses of lignocellulosic biomass. MALDI-imaging can provide data correlating composition and spatial distribution of sugarcane cell wall. Apical and median growth internodes of mature sugarcane (SP80-3280) culms were cut into 2cm blocks, pretreated with ethanol 80% at 80°C, and 50µm sections were cut using a cryostat and mounted in ITO-coated glass slides for MALDI-imaging. An M3+ Sprayer was used to deposit 2,5-dihydroxybenzoic acid (DHB) matrix, added of NaCl 1M. Data were acquired in a Bruker timsTOF flex MALDI-2 instrument, using high intensity laser and MALDI-2 to optimize carbohydrate signal. Analysis of MALDI-image positive data showed that pentose and hexose signals, mostly indicatives of xylans and cellulose, had distinct distributions in apical and median sections, highlighting differences in tissue development, in accordance with known localizations of cellulose and non-branched xylan in the cell wall. Unexpectedly, decorated saccharides, in particular acetylated xylan, whose distributions in situ have not been widely studied, were localized to the vascular tissue. Furthermore, different levels of acetylation (pentoses with degree of polymerization 4 – 8 with to 4 acetyl groups) were located differently on the stelae, with visible changes in localization over the section when comparing apical and median sections, indicating important distinction of the plant’s vascular system in terms of tissue development and providing new insights on acetylated xylan distribution. Such observations impact the understanding of composition and organization of sugarcane vascular system and since highly acetylated polysaccharides are known to be one of the bottlenecks for enzymatic breakdown of lignocellulosic biomass, these results may open new possibilities for the study of cell wall recalcitrance.