title: Thaxtomin A affects CESA-complex density, expression of cell wall genes, cell wall composition, and causes ectopic lignification in Arabidopsis thaliana seedlings.
abstract: Thaxtomin A, a phytotoxin produced by Streptomyces eubacteria, is suspected to act as a natural cellulose synthesis inhibitor. This view is confirmed by the results obtained from new chemical, molecular, and microscopic analyses of Arabidopsis thaliana seedlings treated with thaxtomin A. Cell wall analysis shows that thaxtomin A reduces crystalline cellulose, and increases pectins and hemicellulose in the cell wall. Treatment with thaxtomin A also changes the expression of genes involved in primary and secondary cellulose synthesis as well as genes associated with pectin metabolism and cell wall remodelling, in a manner nearly identical to isoxaben. In addition, it induces the expression of several defence-related genes and leads to callose deposition. Defects in cellulose synthesis cause ectopic lignification phenotypes in A. thaliana, and it is shown that lignification is also triggered by thaxtomin A, although in a pattern different from isoxaben. Spinning disc confocal microscopy further reveals that thaxtomin A depletes cellulose synthase complexes from the plasma membrane and results in the accumulation of these particles in a small microtubule-associated compartment. The results provide new and clear evidence for thaxtomin A having a strong impact on cellulose synthesis, thus suggesting that this is its primary mode of action.
authors.affiliation: Max-Planck Institute for Molecular Plant Physiology, Science Park Golm, Am Mühlenberg 1, 14476 Potsdam, Germany.
authors.forename: Volker
authors.initials: V
authors.lastname: Bischoff
authors.forename: Sarah Jane
authors.initials: SJ
authors.lastname: Cookson
authors.forename: Shuang
authors.initials: S
authors.lastname: Wu
authors.forename: Wolf-Rüdiger
authors.initials: WR
authors.lastname: Scheible
mesh_terms: D017360:Arabidopsis / Q000166:cytology / Q000187:drug effects / Q000235:genetics*; D002247:Carbon Isotopes; D002462:Cell Membrane / Q000187:drug effects / Q000201:enzymology; D002473:Cell Wall / Q000187:drug effects / Q000201:enzymology / Q000235:genetics*; D018506:Gene Expression Regulation, Plant / Q000187:drug effects*; D017343:Genes, Plant; D005964:Glucosyltransferases / Q000378:metabolism*; D007211:Indoles / Q000494:pharmacology*; D008031:Lignin / Q000378:metabolism*; D009097:Multienzyme Complexes / Q000378:metabolism; D010879:Piperazines / Q000494:pharmacology*; D036226:Seedlings / Q000166:cytology / Q000187:drug effects / Q000201:enzymology*
chemical_list: D002247:Carbon Isotopes; D007211:Indoles; D009097:Multienzyme Complexes; D010879:Piperazines; C406691:thaxtomine A; D008031:Lignin; D005964:Glucosyltransferases; C478648:cellulose synthase