title: Physiological characterization and genetic modifiers of aberrant root thigmomorphogenesis in mutants of Arabidopsis thaliana MILDEW LOCUS O genes.
abstract: Root architecture and growth patterns are plant features that are still poorly understood. When grown under in vitro conditions, seedlings with mutations in Arabidopsis thaliana genes MLO4 or MLO11 exhibit aberrant root growth patterns upon contact with hard surfaces, exemplified as tight root spirals. We used a set of physiological assays and genetic tools to characterize this thigmomorphogenic defect in detail. We observed that the mlo4/mlo11-associated root curling phenotype is not recapitulated in a set of mutants with altered root growth patterns or architecture. We further found that mlo4/mlo11-conditioned root curling is not dependent upon light and endogenous flavonoids, but is pH-sensitive and affected by exogenous calcium levels. Based upon the latter two characteristics, mlo4-associated root coiling appears to be mechanistically different from the natural strong root curvature of the Arabidopsis ecotype Landsberg erecta. Gravistimulation reversibly overrides the aberrant thigmomorphogenesis of mlo4 seedlings. Mutants with dominant negative defects in α-tubulin modulate the extent and directionality of mlo4/mlo11-conditioned root coils, whereas mutants defective in polar auxin transport (axr4, aux1) or gravitropism (pgm1) completely suppress the mlo4 root curling phenotype. Our data implicate a joint contribution of calcium signalling, pH regulation, microtubular function, polar auxin transport and gravitropism in root thigmomorphogenesis.
authors.affiliation: Department of Plant-Microbe Interactions, Max-Planck-Institute for Plant Breeding Research, 50829, Cologne, Germany.
authors.forename: Przemyslaw
authors.initials: P
authors.lastname: Bidzinski
authors.forename: Sandra
authors.initials: S
authors.lastname: Noir
authors.forename: Shermineh
authors.initials: S
authors.lastname: Shahi
authors.forename: Anja
authors.initials: A
authors.lastname: Reinstädler
authors.forename: Dominika Marta
authors.initials: DM
authors.lastname: Gratkowska
authors.forename: Ralph
authors.initials: R
authors.lastname: Panstruga
mesh_terms: D017360:Arabidopsis / Q000187:drug effects / Q000235:genetics* / Q000502:physiology*; D029681:Arabidopsis Proteins / Q000235:genetics* / Q000378:metabolism; D001692:Biological Transport / Q000187:drug effects; D002118:Calcium / Q000494:pharmacology; D003624:Darkness; D060146:Ecotype; D004533:Egtazic Acid / Q000494:pharmacology; D005419:Flavonoids / Q000096:biosynthesis; D017343:Genes, Plant / Q000235:genetics*; D016153:Genes, Suppressor; D006112:Gravitation; D006863:Hydrogen-Ion Concentration; D007210:Indoleacetic Acids / Q000378:metabolism; D008870:Microtubules / Q000187:drug effects / Q000378:metabolism; D009024:Morphogenesis / Q000235:genetics*; D009154:Mutation / Q000235:genetics*; D010641:Phenotype; D018517:Plant Roots / Q000235:genetics / Q000254:growth & development*; D014110:Touch
chemical_list: D029681:Arabidopsis Proteins; D005419:Flavonoids; D007210:Indoleacetic Acids; D004533:Egtazic Acid; D002118:Calcium
keywords: MLO; calcium; gravitropism; pH regulation; polar auxin transport; tubulin function