title: Nod factor-induced root hair curling: continuous polar growth towards the point of nod factor application.
abstract: A critical step in establishing a successful nitrogen-fixing symbiosis between rhizobia and legume plants is the entrapment of the bacteria between root hair cell walls, usually in characteristic 180 degrees to 360 degrees curls, shepherd's crooks, which are formed by the host's root hairs. Purified bacterial signal molecules, the nodulation factors (NFs), which are lipochitooligosaccharides, induce root hair deformation in the appropriate host legume and have been proposed to be a key player in eliciting root hair curling. However, for curling to occur, the presence of intact bacteria is thought to be essential. Here, we show that, when spot applied to one side of the growing Medicago truncatula root hair tip, purified NF alone is sufficient to induce reorientation of the root hair growth direction, or a full curl. Using wild-type M. truncatula containing the pMtENOD11::GUS construct, we demonstrate that MtENOD11::GUS is expressed after spot application. The data have been incorporated into a cell biological model, which explains the formation of shepherd's crook curls around NF-secreting rhizobia by continuous tip growth reorientation.
authors.affiliation: Laboratory of Plant Cell Biology, Department of Plant Sciences, Wageningen University, Arboretumlaan 4, 6703 BD Wageningen, The Netherlands.
authors.forename: John J
authors.initials: JJ
authors.lastname: Esseling
authors.forename: Franck G P
authors.initials: FG
authors.lastname: Lhuissier
authors.forename: Anne Mie C
authors.initials: AM
authors.lastname: Emons
mesh_terms: D018506:Gene Expression Regulation, Plant / Q000187:drug effects; D008070:Lipopolysaccharides / Q000494:pharmacology*; D029902:Medicago / Q000166:cytology / Q000187:drug effects* / Q000254:growth & development*; D008565:Membrane Proteins / Q000235:genetics / Q000378:metabolism; D010940:Plant Proteins / Q000235:genetics / Q000378:metabolism; D018517:Plant Roots / Q000166:cytology / Q000187:drug effects* / Q000254:growth & development*
chemical_list: D008070:Lipopolysaccharides; C489058:MTN6 protein, Medicago truncatula; D008565:Membrane Proteins; D010940:Plant Proteins; C045625:nodulin