title: Two seven-transmembrane domain MILDEW RESISTANCE LOCUS O proteins cofunction in Arabidopsis root thigmomorphogenesis.
abstract: Directional root expansion is governed by nutrient gradients, positive gravitropism and hydrotropism, negative phototropism and thigmotropism, as well as endogenous oscillations in the growth trajectory (circumnutation). Null mutations in phylogenetically related Arabidopsis thaliana genes MILDEW RESISTANCE LOCUS O 4 (MLO4) and MLO11, encoding heptahelical, plasma membrane-localized proteins predominantly expressed in the root tip, result in aberrant root thigmomorphogenesis. mlo4 and mlo11 mutant plants show anisotropic, chiral root expansion manifesting as tightly curled root patterns upon contact with solid surfaces. The defect in mlo4 and mlo11 mutants is nonadditive and dependent on light and nutrients. Genetic epistasis experiments demonstrate that the mutant phenotype is independently modulated by the Gbeta subunit of the heterotrimeric G-protein complex. Analysis of expressed chimeric MLO4/MLO2 proteins revealed that the C-terminal domain of MLO4 is necessary but not sufficient for MLO4 action in root thigmomorphogenesis. The expression of the auxin efflux carrier fusion, PIN1-green fluorescent protein, the pattern of auxin-induced gene expression, and acropetal as well as basipetal auxin transport are altered at the root tip of mlo4 mutant seedlings. Moreover, addition of auxin transport inhibitors or the loss of EIR1/AGR1/PIN2 function abolishes root curling of mlo4, mlo11, and wild-type seedlings. These results demonstrate that the exaggerated root curling phenotypes of the mlo4 and mlo11 mutants depend on auxin gradients and suggest that MLO4 and MLO11 cofunction as modulators of touch-induced root tropism.
authors: Department of Biology, University of North Carolina, Chapel Hill, North Carolina 27599, USA.
authors: Zhongying
authors: Z
authors: Chen
authors: Sandra
authors: S
authors: Noir
authors: Mark
authors: M
authors: Kwaaitaal
authors: H Andreas
authors: HA
authors: Hartmann
authors: Ming-Jing
authors: MJ
authors: Wu
authors: Yashwanti
authors: Y
authors: Mudgil
authors: Poornima
authors: P
authors: Sukumar
authors: Gloria
authors: G
authors: Muday
authors: Ralph
authors: R
authors: Panstruga
authors: Alan M
authors: AM
authors: Jones
mesh_terms: D001058:Apomorphine / Q000031:analogs & derivatives / Q000494:pharmacology; D017360:Arabidopsis / Q000187:drug effects / Q000235:genetics / Q000254:growth & development* / Q000378:metabolism; D029681:Arabidopsis Proteins / Q000235:genetics / Q000502:physiology*; D001692:Biological Transport / Q000187:drug effects / Q000235:genetics; D018506:Gene Expression Regulation, Plant / Q000235:genetics / Q000502:physiology; D007210:Indoleacetic Acids / Q000378:metabolism; D008565:Membrane Proteins / Q000235:genetics / Q000502:physiology*; D026901:Membrane Transport Proteins / Q000235:genetics / Q000502:physiology; D018613:Microscopy, Confocal; D018517:Plant Roots / Q000187:drug effects / Q000235:genetics / Q000254:growth & development* / Q000378:metabolism; D030821:Plants, Genetically Modified / Q000235:genetics / Q000254:growth & development; D017434:Protein Structure, Tertiary / Q000235:genetics / Q000502:physiology; D036226:Seedlings / Q000187:drug effects / Q000235:genetics / Q000254:growth & development / Q000378:metabolism
chemical_list: D001058:Apomorphine; D029681:Arabidopsis Proteins; D007210:Indoleacetic Acids; D008565:Membrane Proteins; D026901:Membrane Transport Proteins; C425777:10,11-dihydroxy-N-n-propylnorapomorphine; C117013:AT5G57090 protein, Arabidopsis