Overexpression of the RNA-binding protein NrdA affects global gene expression and secondary metabolism inAspergillusspecies

Abstract

RNA-binding protein Nrd1 plays a role in RNA polymerase II transcription termination. In this study, we showed that the orthologous NrdA is important in global mRNA expression and secondary metabolism in Aspergillus species. We constructed an nrdA conditional expression strain using the Tet-On system in Aspergillus luchuenesis mut. kawachii. Downregulation of nrdA caused a severe growth defect, indicating that NrdA is essential for the proliferation of A. kawachii. Parallel RNA-sequencing and RNA immunoprecipitation-sequencing analysis identified potential NrdA-interacting transcripts, corresponding to 32% of the predicted protein coding genes of A. kawachii. Subsequent gene ontology analysis suggested that overexpression of NrdA affects the production of secondary metabolites. To clarify this, we constructed NrdA-overexpressing strains of Aspergillus nidulans, Aspergillus fumigatus, and Aspergillus oryzae. Overexpression of NrdA reduced the production of sterigmatocystin and penicillin in A. nidulans, as well as that of helvolic acid and pyripyropene A in A. fumigatus. Moreover, it increased the production of kojic acid and reduced production of penicillin in A. oryzae. These effects were accompanied by almost consistent transcriptional changes in the relevant genes. Collectively, these results suggest that NrdA is the essential RNA-binding protein, which plays a significant role in global gene expression and secondary metabolism in Aspergillus species.

Chromosome-level genome sequence data and analysis of the white koji fungus, Aspergillus luchuensis mut. kawachii IFO 4308

“…The obtained chromosomes and mitochondrial DNA were annotated using the Funannotate v1.8.1 pipeline [14] and MFannot v1.1 [15] , respectively. For the Funannotate analysis, the RNA-sequencing (RNA-seq) data for strain IFO 4308 [16] (Sequence Read Archive [SRA] accession numbers SRX9800147 [ https://www.ncbi.nlm.nih.gov/sra/SRX9800147 ] through SRX9800149 [ https://www.ncbi.nlm.nih.gov/sra/SRX9800149 ]) were also used for gene prediction. RNA-seq reads were assembled and mapped using Trinity v2.8.5 [17] and HISAT v2.2.0 [18] , respectively, and gene predictions were updated using PASA v2.4.1.…”