Characterization of hemicellulose in Cunninghamia lanceolata stem during xylogenesis

In this study, hemicellulose was isolated from the apical, middle and basal segments of C. lanceolata stem to investigate the dynamic change of its structure during xylogenesis. Results showed that the C. lanceolata hemicellulose is mainly consisted of O-acetylgalactoglucomannan (GGM) which backbone is alternately linked by & beta;-D-mannopyranosyl (Manp) and & beta;-D-glucopyranosyl (Glcp) via (1 & RARR; 4)-glycosidic bond, while the side chains are & alpha;-D-galactopyranosyl (Galp) and acetyl. In addition, 4-O-methylglucuronoarabinoxylan (GAX) is another dominant structure of C. lanceolata hemicellulose which contains a linear backbone of (1 & RARR; 4)-& beta;-D-xylopyranosyl (Xylp) and side chains of 4-O-Me-& alpha;-D-glucuronic acid (MeGlcpA) and & alpha;-L-arabinofuranose (Araf). The thickness of the cell wall, the ratio of GGM/GAX and the molecular weight of hemicellulose were increased as the extension of growth time. The degree of glycosyl substitutions of xylan and mannan was decreased from 10.34 % (apical) to 8.38 % (basal) and from 15.63 % (apical) to 10.49 % (basal), respectively. However, the total degree of acetylation was enhanced from 0.28 (apical) to 0.37 (basal). Transcriptome analysis showed that genes (CSLA9, IRX9H1, IRX10L, IRX15L, GMGT1, TBL19, TBL25, GUX2, GUX3, GXM1, F8H1 and F8H2) related to hemicellulose biosynthesis are mainly expressed in mature part. This study is of great significance for genetic breeding and high-value utilization of C. lanceolata.

Automated summary

In this study, the hemicellulose composition and structure of C. lanceolata stem during xylogenesis were investigated. The results showed that the hemicellulose in C. lanceolata mainly consisted of O-acetylgalactoglucomannan (GGM) and 4-O-methylglucuronoarabinoxylan (GAX). The thickness of the cell wall and the molecular weight of hemicellulose increased with growth time, while the degree of glycosyl substitutions decreased and the total degree of acetylation increased. Genes related to hemicellulose biosynthesis were mainly expressed in the mature part. This study is of great significance for the genetic breeding and high-value utilization of C. lanceolata.