Temporal and spatial diversities of the immunolabeling of mannan and xylan polysaccharides in differentiating earlywood ray cells and pits of Cryptomeria japonica

Abstract

Wood is composed of various types of cells and each type of cell has different structural and functional properties. However, the temporal and spatial diversities of cell wall components in the cell wall between different cell types are rarely understood. To extend our understanding of distributional diversities of cell wall components among cells, we investigated the immunolabeling of mannans (O-acetyl-galactoglucomannans, GGMs) and xylans (arabino-4-O-methylglucuronoxylans, AGXs) in ray cells and pits. The labeling of GGMs and AGXs was temporally different in ray cells. GGM labeling began to be detected in ray cells at early stages of S₁ formation in tracheids, whereas AGX labeling began to be detected in ray cells at the S₂ formation stage in tracheids. The occurrence of GGM and AGX labeling in ray cells was also temporally different from that of tracheids. AGX labeling began to be detected much later in ray cells than in tracheids. GGM labeling also began to be detected in ray cells either slightly earlier or later than in tracheids. In pits, GGM labeling was detected in bordered and cross-field pit membranes at early stages of pit formation, but not observed in mature pits, indicating that enzymes capable of GGM degradation may be involved in pit membrane formation. In contrast to GGMs, AGXs were not detected in pit membranes during the entire developmental process of bordered and cross-field pits. AGXs showed structural and depositional variations in pit borders depending on the developmental stage of bordered and cross-field pits.