title: The paramutated SULFUREA locus of tomato is involved in auxin biosynthesis.
abstract: The tomato (Solanum lycopersicum) sulfurea mutation displays trans-inactivation of wild-type alleles in heterozygous plants, a phenomenon referred to as paramutation. Homozygous mutant plants and paramutated leaf tissue of heterozygous plants show a pigment-deficient phenotype. The molecular basis of this phenotype and the function of the SULFUREA gene (SULF) are unknown. Here, a comprehensive physiological analysis of the sulfurea mutant is reported which suggests a molecular function for the SULFUREA locus. It is found that the sulf mutant is auxin-deficient and that the pigment-deficient phenotype is likely to represent only a secondary consequence of the auxin deficiency. This is most strongly supported by the isolation of a suppressor mutant which shows an auxin overaccumulation phenotype and contains elevated levels of indole-3-acetic acid (IAA). Several lines of evidence point to a role of the SULF gene in tryptophan-independent auxin biosynthesis, a pathway whose biochemistry and enzymology is still completely unknown. Thus, the sulfurea mutant may provide a promising entry point into elucidating the tryptophan-independent pathway of IAA synthesis.
authors.affiliation: Max-Planck-Institut für Molekulare Pflanzenphysiologie, Am Mühlenberg 1, D-14476 Potsdam-Golm, Germany.
authors.forename: Britta
authors.initials: B
authors.lastname: Ehlert
authors.forename: Mark Aurel
authors.initials: MA
authors.lastname: Schöttler
authors.forename: Gilbert
authors.initials: G
authors.lastname: Tischendorf
authors.forename: Jutta
authors.initials: J
authors.lastname: Ludwig-Müller
authors.forename: Ralph
authors.initials: R
authors.lastname: Bock