title: Wood chemistry analysis and expression profiling of a poplar clone expressing a tyrosine-rich peptide.
abstract: Our study has identified pathways and gene candidates that may be associated with the greater flexibility and digestibility of the poplar cell walls. With the goal of facilitating lignin removal during the utilization of woody biomass as a biofuel feedstock, we previously transformed a hybrid poplar clone with a partial cDNA sequence encoding a tyrosine- and hydroxyproline-rich glycoprotein from parsley. A number of the transgenic lines released more polysaccharides following protease digestion and were more flexible than wild-type plants, but otherwise normal in phenotype. Here, we report that overexpression of the tyrosine-rich peptide encoding sequence in these transgenic poplar plants did not significantly alter total lignin quantity or quality (S/G lignin ratio), five- and six-carbon sugar contents, growth rate, or susceptibility to a major poplar fungal pathogen, Septoria musiva. Whole-genome microarray analysis revealed a total of 411 differentially expressed transcripts in transgenic lines, all with decreased transcript abundance relative to wild-type plants. Their corresponding genes were overrepresented in functional categories such as secondary metabolism, amino acid metabolism, and energy metabolism. Transcript abundance was decreased primarily for five types of genes encoding proteins involved in cell-wall organization and in lignin biosynthesis. The expression of a subset of 19 of the differentially regulated genes by qRT-PCR validated the microarray results. Our study has identified pathways and gene candidates that may be the underlying cause for the enhanced flexibility and digestibility of the stems of poplar plants expressing the TYR transgene.
authors.affiliation: Department of Genetics and Biochemistry, Clemson University, 100 Jordan Hall, Clemson, SC, 29634, USA.
authors.forename: Yi
authors.initials: Y
authors.lastname: Xu
authors.forename: Chin-Fu
authors.initials: CF
authors.lastname: Chen
authors.forename: Tina P
authors.initials: TP
authors.lastname: Thomas
authors.forename: Parastoo
authors.initials: P
authors.lastname: Azadi
authors.forename: Brett
authors.initials: B
authors.lastname: Diehl
authors.forename: Chung-Jui
authors.initials: CJ
authors.lastname: Tsai
authors.forename: Nicole
authors.initials: N
authors.lastname: Brown
authors.forename: John E
authors.initials: JE
authors.lastname: Carlson
authors.forename: Ming
authors.initials: M
authors.lastname: Tien
authors.forename: Haiying
authors.initials: H
authors.lastname: Liang
mesh_terms: D002473:Cell Wall / Q000235:genetics / Q000378:metabolism; D015536:Down-Regulation / Q000235:genetics; D005658:Fungi / Q000502:physiology; D020869:Gene Expression Profiling; D018506:Gene Expression Regulation, Plant; D063990:Gene Ontology; D017343:Genes, Plant / Q000235:genetics; D008031:Lignin / Q000378:metabolism; D058977:Molecular Sequence Annotation; D010455:Peptides / Q000378:metabolism*; D010940:Plant Proteins / Q000235:genetics* / Q000378:metabolism; D018547:Plant Stems / Q000502:physiology; D030821:Plants, Genetically Modified; D032107:Populus / Q000235:genetics* / Q000382:microbiology; D019076:Transgenes; D014443:Tyrosine / Q000378:metabolism*; D014934:Wood / Q000737:chemistry* / Q000235:genetics
chemical_list: D010455:Peptides; D010940:Plant Proteins; D014443:Tyrosine; D008031:Lignin