Carbohydrate-Active Enzymes Involved in the Secondary Cell Wall Biogenesis in Hybrid Aspen

Abstract

Wood formation is a fundamental biological process with significant economic interest. While lignin biosynthesis is currently relatively well understood, the pathways leading to the synthesis of the key structural carbohydrates in wood fibers remain obscure. We have used a functional genomics approach to identify enzymes involved in carbohydrate biosynthesis and remodeling during xylem development in the hybrid aspen Populus tremula × tremuloides. Microarrays containing cDNA clones from different tissue-specific libraries were hybridized with probes obtained from narrow tissue sections prepared by cryosectioning of the developing xylem. Bioinformatic analyses using the sensitive tools developed for carbohydrate-active enzymes allowed the identification of 25 xylem-specific glycosyltransferases belonging to the Carbohydrate-Active EnZYme families GT2, GT8, GT14, GT31, GT43, GT47, and GT61 and nine glycosidases (or transglycosidases) belonging to the Carbohydrate-Active EnZYme families GH9, GH10, GH16, GH17, GH19, GH28, GH35, and GH51. While no genes encoding either polysaccharide lyases or carbohydrate esterases were found among the secondary wall-specific genes, one putative O-acetyltransferase was identified. These wood-specific enzyme genes constitute a valuable resource for future development of engineered fibers with improved performance in different applications.

Absence of branches from xylan in Arabidopsis gux mutants reveals potential for simplification of lignocellulosic biomass

“…S2A). Closely related genes, PttGT8A, PttGT8B, and PttGT8C are expressed during wood formation in poplar (21). However, GUX1 and GUX2 have previously been characterized as the starch initiation proteins PGSIP1 and PGSIP3 (22).…”

Chitinase-Like Protein CTL1 Plays a Role in Altering Root System Architecture in Response to Multiple Environmental Conditions

“…AtCTL1 could play a role in this process if it possesses such a catalytic activity (see later in "Discussion"). Furthermore, CTL1 orthologs in various plant species have been shown to be essential for cell wall structure and cellulose synthesis in both primary and secondary cell walls (Mouille et al, 2003;Aspeborg et al, 2005;Persson et al, 2005;Geisler-Lee et al, 2006). Nevertheless, the exact role of CTL1 in defining the physical properties of the wall remains to be determined.…”

“…The acid moiety of the catalytic site is highly conserved among chitinases between species (Bishop et al, 2000). That residue is replaced by Lys-127 in AtCTL1 as well as in all of the CTL1 ortholog proteins (Aspeborg et al, 2005;Fig. 8).…”

Identification and analysis of expressed sequence tags present in xylem tissues of kelampayan (Neolamarckia cadamba (Roxb.) Bosser)

“…However, the redundancy may increase during further EST sequencing (Li et al 2009). By comparison, the EST redundancy in the kelampayan EST database is comparable to the estimated redundancy of 28 % in Populus (Aspeborg et al 2005) and 28.8 % in Pinus radiata D. Don (Li et al 2009). …”