title: The impact of alterations in lignin deposition on cellulose organization of the plant cell wall.
abstract: BACKGROUND
  Coordination of synthesis and assembly of the polymeric components of cell walls is essential for plant growth and development. Given the degree of co-mingling and cross-linking among cell wall components, cellulose organization must be dependent on the organization of other polymers such as lignin. Here we seek to identify aspects of that codependency by studying the structural organization of cellulose fibrils in stems from Arabidopsis plants harboring mutations in genes encoding enzymes involved in lignin biosynthesis. Plants containing high levels of G-lignin, S-lignin, H-lignin, aldehyde-rich lignin, and ferulic acid-containing lignin, along with plants with very low lignin content were grown and harvested and longitudinal sections of stem were prepared and dried. Scanning X-ray microdiffraction was carried out using a 5-micron beam that moved across the sections in 5-micron steps and complete diffraction patterns were collected at each raster point. Approximately, 16,000 diffraction patterns were analyzed to determine cellulose fibril orientation and order within the tissues making up the stems.
  
  
  RESULTS
  Several mutations-most notably those exhibiting (1) down-regulation of cinnamoyl CoA reductase which leads to cell walls deficient in lignin and (2) defect of cinnamic acid 4-hydroxylase which greatly reduces lignin content-exhibited significant decrease in the proportion of oriented cellulose fibrils in the cell wall. Distinctions between tissues were maintained in all variants and even in plants exhibiting dramatic changes in cellulosic order the trends between tissues (where apparent) were generally maintained. The resilience of cellulose to degradative processes was investigated by carrying out the same analysis on samples stored in water for 30 days prior to data collection. This treatment led to significant loss of cellulosic order in plants rich in aldehyde or H-lignin, less change in wild type, and essentially no change in samples with high levels of G- or S-lignin.
  
  
  CONCLUSIONS
  These studies demonstrate that changes in lignin biosynthesis lead to significant disruption in the orientation and order of cellulose fibrils in all tissues of the stem. These dramatic phenotypic changes, in mutants with lignin rich in aldehyde or H-units, correlate with the impact the mutations have on the enzymatic degradation of the plant cell wall.
authors.affiliation: Department of Bioengineering, Northeastern University, 360 Huntington Ave, Boston, MA 02148 USA.
authors.forename: Jiliang
authors.initials: J
authors.lastname: Liu
authors.affiliation: Department of Biochemistry, Purdue University, 175 South University Street, West Lafayette, IN 47907 USA.
authors.forename: Jeong Im
authors.initials: JI
authors.lastname: Kim
authors.affiliation: Department of Biochemistry, Purdue University, 175 South University Street, West Lafayette, IN 47907 USA.
authors.forename: Joanne C
authors.initials: JC
authors.lastname: Cusumano
authors.affiliation: Department of Biochemistry, Purdue University, 175 South University Street, West Lafayette, IN 47907 USA.
authors.forename: Clint
authors.initials: C
authors.lastname: Chapple
authors.affiliation: GM/CA CAT, XSD, Advanced Photon Source, Argonne National Laboratory, 9700 Cass Ave, Lemont, IL 60439 USA.
authors.forename: Nagarajan
authors.initials: N
authors.lastname: Venugopalan
authors.affiliation: GM/CA CAT, XSD, Advanced Photon Source, Argonne National Laboratory, 9700 Cass Ave, Lemont, IL 60439 USA.
authors.forename: Robert F
authors.initials: RF
authors.lastname: Fischetti
authors.affiliation: Department of Bioengineering, Northeastern University, 360 Huntington Ave, Boston, MA 02148 USA ; Department of Chemistry and Chemical Biology, Northeastern University, 360 Huntington Ave, Boston, MA 02148 USA.
authors.forename: Lee
authors.initials: L
authors.lastname: Makowski
keywords: Cellulose fibril; Lignin biosynthetic mutants; X-ray microdiffraction