Fungal chromatin remodeler Isw1 modulates translation via regulating tRNA transcription.

Chromatin dynamics are essential for regulating DNA processes in response to environmental stimuli. Although ISWI-family enzymes are known to remodel chromatin by sliding nucleosomes in budding yeast, their functional roles and outputs in eukaryotes remain largely unknown. In this study, we investigated chromatin accessibility in the phytopathogenic fungus Fusarium graminearum treated with and without putrescine, a compound that rapidly induces the biosynthesis of the mycotoxin deoxynivalenol (DON). Putrescine globally alters chromatin accessibility, with the ATP-dependent chromatin remodeler FgIsw1 emerging as a key regulator. Unexpectedly, deletion of FgIsw1 did not affect the transcription of DON biosynthesis genes (Tri) but significantly disrupted transfer RNA (tRNA) transcription, leading to a dramatic decline in translation of DON biosynthesis enzymes. Mechanistically, FgIsw1 maintains nucleosome phasing in tRNA chromatin regions, ensuring efficient tRNA transcription. As a result, ΔFgIsw1 was unable to produce DON and lost its virulence on the host plant. These results highlight a novel role of chromatin remodelers in regulating protein translation through the control of tRNA transcription.