The Elongator Subunit Elp3 Regulates Development, Stress Tolerance, Cell Cycle, and Virulence in the Entomopathogenic Fungus Beauveria bassiana

Functional characterization of BbEaf6 in Beauveria bassiana: Implications for fungal virulence and stress response

The Eaf6 protein, a conserved component of the NuA4 and NuA3 complexes in yeast and MOZ/MORF complexes in humans, plays crucial roles in transcriptional activation, gene regulation, and cell cycle control. Despite its significance in other organisms, the functional role of Eaf6 in entomopathogenic fungi (EPF) remained unexplored. Here, we investigate the function of BbEaf6, the Eaf6 homolog in the entomopathogenic fungus Beauveria bassiana. We demonstrate that BbEaf6 is predominantly localized in nuclei, similar to its counterpart in other fungi. Deletion of BbEaf6 resulted in delayed conidiation, reduced conidial yield, and altered conidial properties. Transcriptomic analysis revealed dysregulation of the genes involved in asexual development and cell cycle progression in the ΔBbEaf6 mutant. Furthermore, the ΔBbEaf6 mutant exhibited decreased tolerance to various stresses, including ionic stress, cell wall perturbation, and DNA damage stress. Notably, the ΔBbEaf6 mutant displayed attenuated virulence in insect bioassays, accompanied by dysregulation of genes associated with cuticle penetration and haemocoel infection. Overall, our study elucidates the multifaceted role of BbEaf6 in stress response, development, and virulence in B. bassiana, providing valuable insights into the molecular mechanisms governing fungal pathogenesis and potential targets for pest management strategies.

Functional Characterization of the Histone Acetyltransferase FcElp3 in Lotus Rhizome Rot-Causing Fungus Fusarium commune

Fusarium commune is the main pathogen of lotus rhizome rot, which causes the wilt of many plants. Histone acetyltransferase plays a critical part in the growth and virulence of fungi. In the present study, we identified an FcElp3 in F. commune homologous to histone acetyltransferase Elp3. We further constructed a mutant strain of F. commune to determine the function of FcElp3 in fungal growth and pathogenicity. The results showed that the deletion of FcElp3 resulted in reduced mycelial growth and sporulation. Compared with the wild type, the ΔFcElp3 strain showed more tolerance to osmotic stress and cell wall stress responses but was highly sensitive to oxidative stress. The subcellular localization results indicated that FcElp3 was distributed in both the cytoplasm and nucleus. Western blotting showed that FcElp3 was important for acetylation of H3K14 and H4K8. RNA sequencing analysis showed significant transcriptional changes in the ΔFcElp3 mutant, with 3,098 genes upregulated and 5,770 genes downregulated. Peroxisome was the most significantly enriched metabolic pathway for downregulated genes. This led to a significant decrease in the expression of the core transcription factor Fcap1 involved in the oxidative stress response. Pathogenicity tests revealed that the ΔFcElp3 mutant's pathogenicity on lotus was significantly decreased. Together, these findings clearly demonstrated that FcElp3 was involved in fungal growth, development, stress response, and pathogenicity via the direct regulation of multiple target genes.

Entomopathogenic Fungi in Biological Plant Protection: The Machinery of Multicomponent System Interactions

Plant protection faces a growing number of challenges, partly stemming from intensification of plant cultivation to ensure food security for a rapidly growing global population [...].

Aspergillus fumigatus Elongator complex subunit 3 affects hyphal growth, adhesion and virulence through wobble uridine tRNA modification

The eukaryotic multisubunit Elongator complex has been shown to perform multiple functions in transcriptional elongation, histone acetylation and tRNA modification. However, the Elongator complex plays different roles in different organisms, and the underlying mechanisms remain unexplored. Moreover, the biological functions of the Elongator complex in human fungal pathogens remain unknown. In this study, we verified that the Elongator complex of the opportunistic fungal pathogen Aspergillus fumigatus consists of six subunits (Elp1-6), and the loss of any subunit results in similarly defective colony phenotypes with impaired hyphal growth and reduced conidiation. The catalytic subunit-Elp3 of the Elongator complex includes a S-adenosyl methionine binding (rSAM) domain and a lysine acetyltransferase (KAT) domain, and it plays key roles in the hyphal growth, biofilm-associated exopolysaccharide galactosaminogalactan (GAG) production, adhesion and virulence of A. fumigatus; however, Elp3 does not affect H3K14 acetylation levels in vivo. LC–MS/MS chromatograms revealed that loss of Elp3 abolished the 5-methoxycarbonylmethyl-2-thiouridine (mcm5s2U) modification of tRNA wobble uridine (U34), and the overexpression of tRNAGlnUUG and tRNAGluUUC, which normally harbor mcm5s2U modifications, mainly rescues the defects of the Δelp3 mutant, suggesting that tRNA modification rather than lysine acetyltransferase is responsible for the primary function of Elp3 in A. fumigatus. Strikingly, global proteomic comparison analyses showed significantly upregulated expression of genes related to amino acid metabolism in the Δelp3 mutant strain compared to the wild-type strain. Western blotting showed that deletion of elp3 resulted in overexpression of the amino acid starvation-responsive transcription factor CpcA, and deletion of CpcA markedly reversed the defective phenotypes of the Δelp3 mutant, including attenuated virulence. Therefore, the findings of this study demonstrate that A. fumigatus Elp3 functions as a tRNA-modifying enzyme in the regulation of growth, GAG production, adhesion and virulence by maintaining intracellular amino acid homeostasis. More broadly, our study highlights the importance of U34 tRNA modification in regulating cellular metabolic states and virulence traits of fungal pathogens.