Characterization of hemicellulose in sacred lotus (Nelumbo nucifera Gaetn.) petiole during xylogenesis

Hemicelluloses play a crucial role in connecting cellulose and lignin within the plant cell wall and find extensive biotechnological applications. There is a notable gap in research concerning the hemicellulose from Nelumbo nucifera, the basal eudicot adapted to aquatic environments. To fill this gap, hemicellulose characteristics from the apical to the basal segments of petioles from 4-month-old N. nucifera plants were examined. Results showed that during the initial phase of xylogenesis, xyloglucan predominated in the hemicellulose fraction, while later stages were gradually dominated by 4-O-methyl-D-glucurono-D-xylan (MGX). Having a typical tetrasaccharide reducing end, the glucuronoxylan in N. nucifera was also shown with a typical the MeGlcA on the C2 Xyl carbon sidechain. The total degree of acetylation increased from apex (0.45) to base (0.55) of petiole. Notably, no arabinosyl side-chains were detected in the N. nucifera xylan, suggesting that N. nucifera hemicellulose aligns most closely with dicot wood rather than the non-commelinid monocot (grass). Transcriptomic analysis also indicated that the middle and basal region exhibited higher xylan synthesis activity. This study contributes new evidence supporting the conservation of dicotyledonous hemicellulose during evolution.