title: Cell wall-related proteins of unknown function: missing links in plant cell wall development.
abstract: Lignocellulosic biomass is an important feedstock for the pulp and paper industry as well as emerging biofuel and biomaterial industries. However, the recalcitrance of the secondary cell wall to chemical or enzymatic degradation remains a major hurdle for efficient extraction of economically important biopolymers such as cellulose. It has been estimated that approximately 10-15% of about 27,000 protein-coding genes in the Arabidopsis genome are dedicated to cell wall development; however, only about 130 Arabidopsis genes thus far have experimental evidence validating cell wall function. While many genes have been implicated through co-expression analysis with known genes, a large number are broadly classified as proteins of unknown function (PUFs). Recently the functionality of some of these unknown proteins in cell wall development has been revealed using reverse genetic approaches. Given the large number of cell wall-related PUFs, how do we approach and subsequently prioritize the investigation of such unknown genes that may be essential to or influence plant cell wall development and structure? Here, we address the aforementioned question in two parts; we first identify the different kinds of PUFs based on known and predicted features such as protein domains. Knowledge of inherent features of PUFs may allow for functional inference and a concomitant link to biological context. Secondly, we discuss omics-based technologies and approaches that are helping identify and prioritize cell wall-related PUFs by functional association. In this way, hypothesis-driven experiments can be designed for functional elucidation of many proteins that remain missing links in our understanding of plant cell wall biosynthesis.
authors.affiliation: Department of Genetics, Forestry and Agricultural Biotechnology Institute (FABI), University of Pretoria, Private bag X20, Hatfield, Pretoria, 0028, South Africa.
authors.forename: Ritesh
authors.initials: R
authors.lastname: Mewalal
authors.affiliation: Department of Genetics, Forestry and Agricultural Biotechnology Institute (FABI), University of Pretoria, Private bag X20, Hatfield, Pretoria, 0028, South Africa.
authors.forename: Eshchar
authors.initials: E
authors.lastname: Mizrachi
authors.affiliation: Department of Wood Science, University of British Columbia, Vancouver, BC, V6T 1Z4, Canada.
authors.forename: Shawn D
authors.initials: SD
authors.lastname: Mansfield
authors.affiliation: Department of Genetics, Forestry and Agricultural Biotechnology Institute (FABI), University of Pretoria, Private bag X20, Hatfield, Pretoria, 0028, South Africa zander.myburg@up.ac.za.
authors.forename: Alexander A
authors.initials: AA
authors.lastname: Myburg
mesh_terms: D017360:Arabidopsis / Q000235:genetics / Q000378:metabolism; D018533:Biomass; D002473:Cell Wall / Q000378:metabolism*; D023281:Genomics; D008031:Lignin / Q000096:biosynthesis*; D010940:Plant Proteins / Q000235:genetics / Q000378:metabolism*; D010944:Plants / Q000235:genetics / Q000378:metabolism*; D017434:Protein Structure, Tertiary
chemical_list: D010940:Plant Proteins; C036909:lignocellulose; D008031:Lignin
keywords: Domain of unknown function; Plant cell wall; Proteins of obscure features; Proteins of unknown function