Abstract
Understanding the molecular pathways of plant cell wall biosynthesis and remodeling is central to interpreting biological mechanisms underlying plant growth and adaptation as well as leveraging that knowledge towards development of improved bioenergy feedstocks. Here we report the application of shotgun tandem mass spectrometry profiling to the proteome of Populus developing xylem. Additionally, we mined public databases to obtain information in support of subcellular localization, transcript-level expression, and functional categorization of these proteins. Nearly 6000 different proteins were identified from the xylem proteome, with over 4400 proteins identified from one or more unique peptides. In addition to finding protein-level evidence of candidate wall biosynthesis genes from xylem (wood) tissue such as cellulose synthase, phenylalanine ammonia-lyase, and 4-coumarate:CoA ligase, several other potentially new candidate genes in the pathway were discovered. In order to identify low-abundance DNA-regulatory proteins from the developing xylem, a selective nuclear proteome profiling method was developed. Several putative transcription factor and chromatin remodeling proteins were identified using this method, such as LIM and NAC domain transcription factors and CHB3-SWI/SNF-related proteins. Further application of these proteomics methods will enhance understanding not only of cell wall biosynthesis in system biology modeling, but also other plant developmental and physiological pathways.
