Carbohydrate-related genes and cell wall biosynthesis in vascular tissues of loblolly pine (Pinus taeda)
Campbell J. Nairn (1, 2), Denise M. Lennon (1), Alicia Wood-Jones (1), Alison V. Nairn (3) and Jeffrey F. D. Dean (1)
1. Warnell School of Forestry and Natural Resources, University of Georgia, Athens, GA 30602, USA / 2. Corresponding author () / 3. Complex Carbohydrate Research Center, University of Georgia, Athens, GA 30602, USA / Received June 25, 2007; accepted August 3, 2007; published online May 1, 2008
Summary
Loblolly pine (Pinus taeda L.), the most widely planted tree species in the United States, is an important source of wood and wood fibers for a multitude
of consumer products. Wood fibers are primarily composed of secondary cell walls, and cellulose, hemicelluloses and lignin
are major components of wood. Fiber morphology and cell wall composition are important determinants of wood properties. We
used comparative genomics to identify putative genes for cellulose and hemicellulose synthesis in loblolly pine that are homologous
to genes implicated in cell wall synthesis in angiosperms. Sequences encoding putative secondary cell wall cellulose synthase
genes, cellulose synthase-like genes, a membrane-bound endoglucanase gene, a sucrose synthase gene, a UDP-glucose pyrophosphorylase
gene and GDP-mannose pyrophosphorylase genes were identified in expressed sequence tag (EST) collections from loblolly pine.
Full-length coding sequences were obtained from cDNA clones isolated from a library constructed from developing xylem. Phylogenetic
relationships between the genes from loblolly pine and angiosperm taxa were examined and transcriptional profiling in vascular
tissues was conducted by real-time quantitative, reverse transcriptase-polymerase chain reaction. The putative cell wall synthesis
genes were expressed at high levels in vascular tissues and a subset was differentially regulated in xylem and phloem tissues.
Inferred phylogenetic relationships and expression patterns for the genes from loblolly pine were consistent with roles in
synthesis of complex carbohydrates of the cell wall. These studies suggest functional conservation of homologous wood formation
genes in gymnosperm and angiosperm taxa.
