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4. Assembly, Architecture, and Growth

The mechanisms of assembly of non-cellulosic, cross-linking glycans and the formation of a precisely arranged pectin matrix around this composite are not well understood. The expansins and yieldins represent two types of proteins that function in wall loosening, as deduced from demonstration of wall extension in vitro. Xyloglucan endotransglucosylases (XETs) also function in remodeling or restructuring of the wall during growth and after wall extension has ceased. They are members of a large family of genes that encode both strict and facultative transglucosylases and xyloglucan hydrolases (XEHs), collectively known as the XTH family. Determining the role of the individual members is a major challenge.

  4.1 Growth modifying proteins
      4.1.1 Expansins
      4.1.2 Yieldins
  4.2 Xyloglucan endotransglucosylase/hydrolases
  4.3 Hydrolases
      4.3.1 Exo-acting glycanases
 ß-Galactosidase family 35
      4.3.2 Endo-acting glycanases
 Glycoside hydrolase family 9 (Endo-1,4-beta-glucanase)
 Glycoside hydrolase family 17 (Glucan endo-1,3-beta-glucosidase)
      4.3.3 Polygalacturonases - PGases
  4.4 Lyases
      4.4.1 Pectate and pectin Lyases
      4.4.2 Rhamnogalacturonan I lyases
  4.5 Esterases
      4.5.1 Pectin methyl esterases
      4.5.2 Pectin acetylestereases
      4.5.3 Feruloyl esterases
  4.6 Structural proteins
      4.6.1 Hydroxyproline-rich glycoproteins (HRGPs)
      4.6.2 Proline-rich proteins (PRPs)
      4.6.3 Glycine-rich proteins (GRPs)
      4.6.4 Arabinogalactan-proteins (AGPs)
      4.6.5 Prolyl-4-hydroxylases

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