title: Perturbation of Brachypodium distachyon CELLULOSE SYNTHASE A4 or 7 results in abnormal cell walls.
abstract: BACKGROUND
  Cellulose is an integral component of the plant cell wall and accounts for approximately forty percent of total plant biomass but understanding its mechanism of synthesis remains elusive. CELLULOSE SYNTHASE A (CESA) proteins function as catalytic subunits of a rosette-shaped complex that synthesizes cellulose at the plasma membrane. Arabidopsis thaliana and rice (Oryza sativa) secondary wall CESA loss-of-function mutants have weak stems and irregular or thin cell walls.
  
  
  RESULTS
  Here, we identify candidates for secondary wall CESAs in Brachypodium distachyon as having similar amino acid sequence and expression to those characterized in A. thaliana, namely CESA4/7/8. To functionally characterize BdCESA4 and BdCESA7, we generated loss-of-function mutants using artificial microRNA constructs, specifically targeting each gene driven by a maize (Zea mays) ubiquitin promoter. Presence of the transgenes reduced BdCESA4 and BdCESA7 transcript abundance, as well as stem area, cell wall thickness of xylem and fibers, and the amount of crystalline cellulose in the cell wall.
  
  
  CONCLUSIONS
  These results suggest BdCESA4 and BdCESA7 play a key role in B. distachyon secondary cell wall biosynthesis.
authors.affiliation: Biology Department, University of Massachusetts, Amherst, MA, USA. hazen@bio.umass.edu.
authors.forename: Pubudu P
authors.initials: PP
authors.lastname: Handakumbura
authors.forename: Dominick A
authors.initials: DA
authors.lastname: Matos
authors.forename: Karen S
authors.initials: KS
authors.lastname: Osmont
authors.forename: Michael J
authors.initials: MJ
authors.lastname: Harrington
authors.forename: Kyuyoung
authors.initials: K
authors.lastname: Heo
authors.forename: Kabindra
authors.initials: K
authors.lastname: Kafle
authors.forename: Seong H
authors.initials: SH
authors.lastname: Kim
authors.forename: Tobias I
authors.initials: TI
authors.lastname: Baskin
authors.forename: Samuel P
authors.initials: SP
authors.lastname: Hazen
mesh_terms: D058431:Brachypodium / Q000201:enzymology* / Q000378:metabolism*; D002473:Cell Wall / Q000201:enzymology* / Q000378:metabolism*; D018506:Gene Expression Regulation, Plant; D005964:Glucosyltransferases / Q000235:genetics / Q000378:metabolism*; D010802:Phylogeny; D010940:Plant Proteins / Q000235:genetics / Q000378:metabolism; D030821:Plants, Genetically Modified / Q000201:enzymology / Q000378:metabolism
chemical_list: D010940:Plant Proteins; D005964:Glucosyltransferases; C478648:cellulose synthase
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