Mutations inArabidopsis thalianagenes involved in the tryptophan biosynthesis pathway affect root waving on tilted agar surfaces

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Abstract
Summary: Arabidopsis thaliana roots grow in a wavy pattern upon a slanted surface. A novel mutation in the anthranilate synthase α1 ( ASA1 ) gene, named trp5–2wvc1 , and mutations in the tryptophan synthase α and β1 genes ( trp3–1 and trp2–1 , respectively) confer a compressed root wave phenotype on tilted agar surfaces. When trp5–2wvc1 seedlings are grown on media supplemented with anthranilate metabolites, their roots wave like wild type. Genetic and pharmacological experiments argue that the compressed root wave phenotypes of trp5–2wvc1 , trp2–1 and trp3–1 seedlings are not due to reduced IAA biosynthetic potential, but rather to a deficiency in L‐tryptophan (L‐Trp), or in a L‐Trp derivative. Although the roots of 7‐day‐old seedlings possess higher concentrations of free L‐Trp than the shoot as a whole, trp5–2wvc1 mutants show no detectable alteration in L‐Trp levels in either tissue type, suggesting that a very localized shortage of L‐Trp, or of a L‐Trp‐derived compound, is responsible for the observed phenotype.