| Summary: | Leptosphaeria maculans is the causal agent of blackleg disease in Brassica napus. In this thesis the ability of L. maculans to produce certain phytohormones was established. The thesis focused on auxins and brassinosteroids. Most commonly occurring natural auxin, IAA, and its inactive oxidation product, OxIAA, were found in highest concentration. In plants infected with L. maculans the concentration of OxIAA was higher when compared to control water- treated plants. A surprising difference in IAA production between two sister isolates of L. maculans was discovered. In chemically defined cultivation medium Gamborg JN2 isolate did not produce any IAA. JN3 on the other hand produced IAA in concentration around 1000 pmol/g FW. This difference was used for studying L. maculans putative auxin synthesizing genes. The candidate genes were identified as orthologs of Arabidopsis thaliana genes (YUCCA1.1, NIT1.2) and Ustilago maydis (IAD1.2, TAM1-2.1). An increased transcription level of the auxin biosynthesis candidate genes was observed in JN2 treated in vitro with auxin precursors (tryptophan, tryptamine). Increased IAA concentration was observed as well. No such effect was observed in JN3. Surprisingly, an increased candidate gene transcription and IAA concentration was observed also in JN2 treated with...
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