title: Activation tagging of Arabidopsis POLYGALACTURONASE INVOLVED IN EXPANSION2 promotes hypocotyl elongation, leaf expansion, stem lignification, mechanical stiffening, and lodging.
abstract: Pectin is the most abundant component of primary cell walls in eudicot plants. The modification and degradation of pectin affects multiple processes during plant development, including cell expansion, organ initiation, and cell separation. However, the extent to which pectin degradation by polygalacturonases affects stem development and secondary wall formation remains unclear. Using an activation tag screen, we identified a transgenic Arabidopsis thaliana line with longer etiolated hypocotyls, which overexpresses a gene encoding a polygalacturonase. We designated this gene as POLYGALACTURONASE INVOLVED IN EXPANSION2 (PGX2), and the corresponding activation tagged line as PGX2AT. PGX2 is widely expressed in young seedlings and in roots, stems, leaves, flowers, and siliques of adult plants. PGX2-GFP localizes to the cell wall, and PGX2ATplants show higher total polygalacturonase activity and smaller pectin molecular masses than wild-type controls, supporting a function for this protein in apoplastic pectin degradation. A heterologously expressed, truncated version of PGX2 also displays polygalacturonase activity in vitro. Like previously identified PGX1ATplants, PGX2ATplants have longer hypocotyls and larger rosette leaves, but they also uniquely display early flowering, earlier stem lignification, and lodging stems with enhanced mechanical stiffness that is possibly due to decreased stem thickness. Together, these results indicate that PGX2 both functions in cell expansion and influences secondary wall formation, providing a possible link between these two developmental processes.
authors.affiliation: Department of Biology, The Pennsylvania State University, University Park, PA 16802, USA.|Center for Lignocellulose Structure and Formation, The Pennsylvania State University, University Park, PA 16802, USA.
authors.forename: Chaowen
authors.initials: C
authors.lastname: Xiao
authors.affiliation: Department of Biology, The Pennsylvania State University, University Park, PA 16802, USA.|Center for Lignocellulose Structure and Formation, The Pennsylvania State University, University Park, PA 16802, USA.
authors.forename: William J
authors.initials: WJ
authors.lastname: Barnes
authors.affiliation: Department of Agricultural and Biological Engineering, The Pennsylvania State University, University Park, PA 16802, USA.
authors.forename: M Shafayet
authors.initials: MS
authors.lastname: Zamil
authors.affiliation: Department of Agricultural and Biological Engineering, The Pennsylvania State University, University Park, PA 16802, USA.
authors.forename: Hojae
authors.initials: H
authors.lastname: Yi
authors.affiliation: Department of Agricultural and Biological Engineering, The Pennsylvania State University, University Park, PA 16802, USA.
authors.forename: Virendra M
authors.initials: VM
authors.lastname: Puri
authors.affiliation: Department of Biology, The Pennsylvania State University, University Park, PA 16802, USA.|Center for Lignocellulose Structure and Formation, The Pennsylvania State University, University Park, PA 16802, USA.
authors.forename: Charles T
authors.initials: CT
authors.lastname: Anderson
mesh_terms: D017360:Arabidopsis / Q000235:genetics / Q000254:growth & development* / Q000378:metabolism*; D029681:Arabidopsis Proteins / Q000235:genetics / Q000378:metabolism*; D002473:Cell Wall / Q000378:metabolism; D018506:Gene Expression Regulation, Plant / Q000235:genetics / Q000502:physiology; D018546:Hypocotyl / Q000235:genetics / Q000254:growth & development* / Q000378:metabolism*; D008031:Lignin / Q000378:metabolism; D010368:Pectins / Q000378:metabolism; D018515:Plant Leaves / Q000235:genetics / Q000254:growth & development / Q000378:metabolism*; D018547:Plant Stems / Q000235:genetics / Q000254:growth & development / Q000378:metabolism*; D030821:Plants, Genetically Modified / Q000235:genetics / Q000254:growth & development / Q000378:metabolism; D011096:Polygalacturonase / Q000378:metabolism
chemical_list: D029681:Arabidopsis Proteins; D010368:Pectins; D008031:Lignin; D011096:Polygalacturonase
keywords: 
  Arabidopsis thaliana
  ; cell expansion; cell wall; lignin; pectin; polygalacturonase; stem lodging