The Lsm1–7 complex couples 3′-end protection to histone H4 acetylation to maintain mRNA homeostasis in Fusarium graminearum

TL;DR

This study reveals how the Lsm1–7 complex in the fungus Fusarium graminearum helps maintain mRNA balance by protecting RNA ends and influencing gene expression.

Contribution

The study identifies a new regulatory mechanism involving Lsm1–7 and chromatin modifications to maintain mRNA homeostasis in fungal pathogens.

Findings

Lsm1–7 localizes to P-bodies and is essential for fungal growth, virulence, and mycotoxin production.

Lsm1–7 protects U/A-rich 3′ ends of transcripts and inhibits their decay via two parallel pathways.

Loss of Lsm1–7 triggers a compensatory transcriptional response involving histone H4 acetylation.

Abstract

Eukaryotic messenger RNA (mRNA) homeostasis requires precise coordination between synthesis and decay, yet the mechanisms governing this balance in fungal pathogens remain elusive. Here we provide a comprehensive characterization of the Lsm1–7 complex in the cereal pathogen Fusarium graminearum. We show that Lsm1–7 assembles into a conserved hetero-heptameric module that localizes to processing bodies (P-bodies) and is required for fungal growth, virulence, and mycotoxin biosynthesis. Mechanistically, Lsm1–7/Pat1 binds U/A-rich 3′ termini of a defined set of transcripts enriched for central metabolism and restrains their 3′–5′ decay. Genetic suppressor analyses and mechanistic dissection identify two parallel decay routes antagonized by Lsm1–7, including the exosome recruited by the uridyltransferase Cid1 and the Ski–exosome complex mediated by the newly identified scaffold protein Lsp1. Moreover, loss of Lsm1–7 elicits a compensatory transcriptional response involving the Rpd3L (Sin3) histone deacetylase complex, in which elevated histone H4 acetylation at affected loci partially restores transcript output. Together, our results define an integrated cytoplasmic–nuclear regulatory axis in F. graminearum that couples 3′-end protection to chromatin-based transcriptional buffering to maintain mRNA homeostasis. While Lsp1 appears lineage-adapted, the underlying logic may reflect a broader principle of gene-expression buffering that supports fungal fitness and pathogenicity.

Graphical Abstract

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