A conserved Lsm8–exosome module maintains RNA splicing fidelity to control fungal stress adaptation and virulence

Abstract

Fusarium graminearum, the causal agent of Fusarium head blight (FHB), poses a major threat to global food security by contaminating cereals with the mycotoxin deoxynivalenol (DON). Although transcriptional and protein-level regulation of its stress response and virulence has been extensively studied, the functional significance of mRNA processing in these critical processes remains largely unexplored. Here, we identify Lsm8, a highly conserved core subunit of the nuclear Lsm2-8 complex, as a pivotal regulator linking RNA splicing fidelity to fungal growth, stress adaptation, and virulence. Deletion of LSM8 disrupted Lsm2-8 assembly and nuclear localization, resulting in widespread intron retention in genes essential for stress signaling (HOG1, ATF1), development (GPA1, STE12), and trichothecene biosynthesis. Consequently, osmoadaptation was impaired, sexual reproduction was abolished, and both DON production and virulence were drastically reduced. We further demonstrate that intron-retained transcripts are predominantly degraded by the RNA exosome, revealing a conserved Lsm8–exosome module that maintains splicing fidelity and RNA surveillance. Given the deep evolutionary conservation of Lsm8 across eukaryotes, these findings uncover a fundamental post-transcriptional regulatory layer governing fungal stress response, virulence, and mycotoxin biosynthesis, and highlight RNA-processing factors as universal determinants of virulence and promising antifungal targets across eukaryotic pathogens.

Keywords

Lsm2-8 complex / RNA splicing fidelity / RNA exosome / Post-transcriptional regulation / Intron retention / Stress response / Fungal virulence / Mycotoxin biosynthesis / Fusarium graminearum

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Funding

National Key R&D Program of China (2023YFC2606800)

National Natural Science Foundation(32172356)

the Natural Science Foundation of Zhejiang Province(LZ23C140004)

Pioneer and Leading Goose R&D Program of Zhejiang(2023C02030)

China Agriculture Research System(CARS-3-1-15)

Fundamental Research Funds for the Central Universities(226-2024-00213)

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The Author(s)