Auxins are hormones that regulate growth and development in plants. Besides plants, various microorganisms also produce auxins. Here we investigate whether and how the phytopathogenic fungus Leptosphaeria maculans biosynthesizes auxins. We characterized the auxin profile of in vitro grown L. maculans. The culture was further supplied with the auxin biosynthetic-precursors tryptophan and tryptamine and gene expression and phytohormone content was analyzed. L. maculans in vitro produced IAA (indole-3-acetic acid) as the predominant auxin metabolite. IAA production could be further stimulated by supplying precursors. Expression of indole-3-pyruvate decarboxylase LmIPDC2, tryptophan aminotransferase LmTAM1 and nitrilase LmNIT1 genes was mainly upregulated after adding tryptophan and correlated with IAA production, suggesting that these genes are the key components of auxin biosynthesis in L. maculans. Tryptamine acted as a potent inducer of IAA production, though a pathway independent of LmIPDC2/LmTAM1 may be involved. Despite L. maculans being a rich source of bioactive IAA, the auxin metabolic profile of host plant Brassica napus was not altered upon infection. Exogenous IAA inhibited the growth of L. maculans in vitro when supplied in high concentration. Altogether, we showed that L. maculans is capable of IAA production and we have identified biosynthetic genes that were responsive to tryptophan treatment.
- MeSH
- aminohydrolasy genetika MeSH
- biosyntetické dráhy MeSH
- Brassica napus mikrobiologie MeSH
- fylogeneze MeSH
- genetická transkripce MeSH
- houby klasifikace genetika metabolismus MeSH
- karboxylyasy genetika metabolismus MeSH
- kyseliny indoloctové metabolismus farmakologie MeSH
- Leptosphaeria enzymologie genetika růst a vývoj metabolismus MeSH
- regulace genové exprese u hub MeSH
- regulátory růstu rostlin metabolismus MeSH
- tryptaminy metabolismus farmakologie MeSH
- tryptofan metabolismus farmakologie MeSH
- tryptofantransaminasa genetika metabolismus MeSH
- upregulace MeSH
- Publikační typ
- časopisecké články MeSH
Identification of mutants with impairments in auxin biosynthesis and dynamics by forward genetic screening is hindered by the complexity, redundancy and necessity of the pathways involved. Furthermore, although a few auxin-deficient mutants have been recently identified by screening for altered responses to shade, ethylene, N-1-naphthylphthalamic acid (NPA) or cytokinin (CK), there is still a lack of robust markers for systematically isolating such mutants. We hypothesized that a potentially suitable phenotypic marker is root curling induced by CK, as observed in the auxin biosynthesis mutant CK-induced root curling 1 / tryptophan aminotransferase of Arabidopsis 1 (ckrc1/taa1). Phenotypic observations, genetic analyses and biochemical complementation tests of Arabidopsis seedlings displaying the trait in large-scale genetic screens showed that it can facilitate isolation of mutants with perturbations in auxin biosynthesis, transport and signaling. However, unlike transport/signaling mutants, the curled (or wavy) root phenotypes of auxin-deficient mutants were significantly induced by CKs and could be rescued by exogenous auxins. Mutants allelic to several known auxin biosynthesis mutants were re-isolated, but several new classes of auxin-deficient mutants were also isolated. The findings show that CK-induced root curling provides an effective marker for discovering genes involved in auxin biosynthesis or homeostasis.
- MeSH
- Arabidopsis enzymologie genetika MeSH
- biologický transport účinky léků MeSH
- cytokininy metabolismus MeSH
- fenotyp MeSH
- kořeny rostlin enzymologie genetika růst a vývoj MeSH
- kyseliny indoloctové metabolismus farmakologie MeSH
- mutace MeSH
- proteiny huseníčku genetika metabolismus MeSH
- regulátory růstu rostlin biosyntéza MeSH
- semenáček účinky léků růst a vývoj metabolismus MeSH
- signální transdukce účinky léků MeSH
- tryptofantransaminasa genetika metabolismus MeSH
- Publikační typ
- časopisecké články MeSH
- práce podpořená grantem MeSH
