title: Lipid transfer proteins enhance cell wall extension in tobacco.
abstract: Plant cells are enclosed by a rigid cell wall that counteracts the internal osmotic pressure of the vacuole and limits the rate and direction of cell enlargement. When developmental or physiological cues induce cell extension, plant cells increase wall plasticity by a process called loosening. It was demonstrated previously that a class of proteins known as expansins are mediators of wall loosening. Here, we report a type of cell wall-loosening protein that does not share any homology with expansins but is a member of the lipid transfer proteins (LTPs). LTPs are known to bind a large range of lipid molecules to their hydrophobic cavity, and we show here that this cavity is essential for the cell wall-loosening activity of LTP. Furthermore, we show that LTP-enhanced wall extension can be described by a logarithmic time function. We hypothesize that LTP associates with hydrophobic wall compounds, causing nonhydrolytic disruption of the cell wall and subsequently facilitating wall extension.
authors.affiliation: Institute for Wetland and Water Research, Department of Experimental Botany, Radboud University Nijmegen, 6525 ED Nijmegen, The Netherlands. j.nieuwland@biotech.cam.ac.uk
authors.forename: Jeroen
authors.initials: J
authors.lastname: Nieuwland
authors.forename: Richard
authors.initials: R
authors.lastname: Feron
authors.forename: Bastiaan A H
authors.initials: BA
authors.lastname: Huisman
authors.forename: Annalisa
authors.initials: A
authors.lastname: Fasolino
authors.forename: Cornelis W
authors.initials: CW
authors.lastname: Hilbers
authors.forename: Jan
authors.initials: J
authors.lastname: Derksen
authors.forename: Celestina
authors.initials: C
authors.lastname: Mariani
mesh_terms: D001665:Binding Sites / Q000502:physiology; D002352:Carrier Proteins / Q000235:genetics / Q000302:isolation & purification / Q000378:metabolism*; D002454:Cell Differentiation / Q000502:physiology; D049108:Cell Enlargement; D002473:Cell Wall / Q000378:metabolism*; D008563:Membrane Lipids / Q000737:chemistry / Q000378:metabolism*; D008969:Molecular Sequence Data; D010940:Plant Proteins / Q000235:genetics / Q000302:isolation & purification / Q000378:metabolism*; D017434:Protein Structure, Tertiary / Q000502:physiology; D017386:Sequence Homology, Amino Acid; D012689:Sequence Homology, Nucleic Acid; D013997:Time Factors; D014026:Nicotiana / Q000254:growth & development / Q000378:metabolism*
chemical_list: D002352:Carrier Proteins; C109356:LTP2 protein, plant; D008563:Membrane Lipids; D010940:Plant Proteins; C095825:expansin protein, plant