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

## TL;DR

This study shows that the Lsm8 protein helps fungi like Fusarium graminearum properly process RNA, which is crucial for their stress response, reproduction, and toxin production.

## Contribution

The study identifies a conserved Lsm8–exosome module that regulates RNA splicing fidelity in fungi, linking it to stress adaptation and virulence.

## Key findings

- Deleting LSM8 disrupted RNA splicing and caused intron retention in key genes for stress and virulence.
- Intron-retained transcripts were degraded by the RNA exosome, revealing a conserved RNA surveillance mechanism.
- Lsm8 is essential for fungal osmoadaptation, sexual reproduction, and mycotoxin production.

## 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.

The online version contains supplementary material available at 10.1007/s44154-026-00285-6.