AUTHOR=Gaffar Fatima Yousif , Imani Jafargholi , Karlovsky Petr , Koch Aline , Kogel Karl-Heinz 

TITLE=Different Components of the RNA Interference Machinery Are Required for Conidiation, Ascosporogenesis, Virulence, Deoxynivalenol Production, and Fungal Inhibition by Exogenous Double-Stranded RNA in the Head Blight Pathogen Fusarium graminearum

JOURNAL=Frontiers in Microbiology

VOLUME=10

YEAR=2019

URL=https://www.frontiersin.org/journals/microbiology/articles/10.3389/fmicb.2019.01662

DOI=10.3389/fmicb.2019.01662

ISSN=1664-302X

ABSTRACT=<p>In filamentous fungi, gene silencing through RNA interference (RNAi) shapes many biological processes, including pathogenicity. We explored the requirement of key components of fungal RNAi machineries, including DICER-like 1 and 2 (<italic>Fg</italic>DCL1, <italic>Fg</italic>DCL2), ARGONAUTE 1 and 2 (<italic>Fg</italic>AGO1, <italic>Fg</italic>AGO2), AGO-interacting protein <italic>Fg</italic>QIP (QDE2-interacting protein), RecQ helicase (<italic>Fg</italic>QDE3), and four RNA-dependent RNA polymerases (<italic>Fg</italic>RdRP1, <italic>Fg</italic>RdRP2, <italic>Fg</italic>RdRP3, <italic>Fg</italic>RdRP4), in the ascomycete mycotoxin-producing fungal pathogen <italic>Fusarium graminearum</italic> (<italic>Fg</italic>) for sexual and asexual multiplication, pathogenicity, and its sensitivity to double-stranded (ds)RNA. We corroborate and extend earlier findings that conidiation, ascosporogenesis, and Fusarium head blight (FHB) symptom development require an operable RNAi machinery. The involvement of RNAi in conidiation is dependent on environmental conditions as it is detectable only under low light (&lt;2 μmol m<sup>−2</sup> s<sup>−1</sup>). Although both DCLs and AGOs partially share their functions, the sexual ascosporogenesis is mediated primarily by <italic>Fg</italic>DCL1 and <italic>Fg</italic>AGO2, while <italic>Fg</italic>DCL2 and <italic>Fg</italic>AGO1 contribute to asexual conidia formation and germination. <italic>Fg</italic>DCL1 and <italic>Fg</italic>AGO2 also account for pathogenesis as their knockout (KO) results in reduced FHB development. Apart from KO mutants <italic>Δdcl2</italic> and <italic>Δago1</italic>, mutants <italic>Δrdrp2</italic>, <italic>Δrdrp3</italic>, <italic>Δrdrp4</italic>, <italic>Δqde3</italic>, and <italic>Δqip</italic> are strongly compromised for conidiation, while KO mutations in all <italic>RdPRs</italic>, <italic>QDE3</italic>, and <italic>QIP</italic> strongly affect ascosporogenesis. Analysis of trichothecenes mycotoxins in wheat kernels showed that the relative amount of deoxynivalenol (DON), calculated as [DON] per amount of fungal genomic DNA was reduced in all spikes infected with RNAi mutants, suggesting the possibility that the fungal RNAi pathways affect <italic>Fg</italic>’s DON production. Moreover, silencing of fungal genes by exogenous target gene-specific double-stranded RNA (dsRNA) (spray-induced gene silencing, SIGS) is dependent on DCLs, AGOs, and QIP, but not on QDE3. Together these data show that in <italic>F. graminearum</italic>, different key components of the RNAi machinery are crucial in different steps of fungal development and pathogenicity.</p>