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Arabidopsis thaliana seedling growth with pure oxylipins resulted in root waving, loss of root apical dominance, and decreased root elongation. 9-Hydroxyoctadecatrienoic acid (9-HOT) was a potent inducer of root waving. Studies with noxy2 (for nonresponding to oxylipins2), a new 9-HOT-insensitive mutant, and coronatine insensitive1-1 (jasmonate-insensitive) revealed at least three signaling cascades mediating the oxylipin actions. Treatment with 9-HOT resulted in a reduction in lateral roots and an increase in stage V primordia. Roots showed strong 9-lipoxygenase (9-LOX) activity, and root primordia expressed 9-LOX genes. These results, along with findings that noxy2 and mutants with defective 9-LOX activity showed increased numbers of lateral roots, suggest that 9-HOT, or a closely related 9-LOX product, is an endogenous modulator of lateral root formation. Histochemical and molecular analyses revealed that 9-HOT activated events common to development and defense responses. A subset of 9-HOT-responding root genes was also induced in leaves after 9-HOT treatment or pathogen inoculation. The results that noxy2 displayed altered root development, enhanced susceptibility to Pseudomonas, and reduced the activation of 9-HOT-responding genes are consistent with mechanistic links among these processes. The nature of the changes detected suggests that oxylipins from the 9-LOX pathway function in cell wall modifications required for lateral root development and pathogen arrest.

Original publication

DOI

10.1105/tpc.106.046052

Type

Journal article

Journal

Plant Cell

Publication Date

03/2007

Volume

19

Pages

831 - 846

Keywords

Arabidopsis, Arabidopsis Proteins, Gene Expression Regulation, Plant, Genes, Plant, Linolenic Acids, Lipoxygenase, Models, Biological, Mutant Proteins, Mutation, Oxidation-Reduction, Phenotype, Plant Leaves, Plant Roots, Polysaccharides, Reactive Oxygen Species, Seedlings, Signal Transduction