Auxin biosynthesis in the phytopathogenic fungus Leptosphaeria maculans is associated with enhanced transcription of indole-3-pyruvate decarboxylase LmIPDC2 and tryptophan aminotransferase LmTAM1
2020
Leontovyčová, Hana | Trdá, Lucie | Dobrev, Petre Ivanov | Šašek, Vladimír | Gay, Elise | Balesdent, Marie‐hélène | Burketová, Lenka | Institute of Experimental Botany of the Czech Academy of Sciences (IEB / CAS) ; Czech Academy of Sciences [Prague] (CAS) | Přírodovědecká fakulta, Univerzita Karlova [Praha, Česká republika] = Faculty of Sciences, Charles University [Prague, Czech Republic] (PřF UK) ; Univerzita Karlova [Praha, Česká republika] = Charles University [Prague, Czech Republic] = Université Charles [Prague, Republique tchèque] (UK) | BIOlogie et GEstion des Risques en agriculture (BIOGER) ; AgroParisTech-Université Paris-Saclay-Institut National de Recherche pour l’Agriculture, l’Alimentation et l’Environnement (INRAE) | funding n° GAUK 992416, SVV260427/2019, Czech Grant Agency, Czech Republic (Grantová agentura České Republiky)-funding n° 13-26798S
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Show more [+] Less [-]English. 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 invitro 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 invitro 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 invitro 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.
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