Genome-wide exonic small interference RNA-mediated gene silencing regulates sexual reproduction in the homothallic fungus Fusarium graminearum

Various ascomycete fungi possess sex-specific molecular mechanisms,such as repeat-induced point mutations,meiotic silencing by unpaired dna,and unusual adenosine-to-inosine rna editing,for genome defense or gene regulation. using a combined analysis of functional genetics and deep sequencing of small noncoding rna (srna),mrna,and the degradome,we found that the sex-specifically induced exonic small interference rna (ex-sirna)-mediated rna interference (rnai) mechanism has an important role in fine-tuning the transcriptome during ascospore formation in the head blight fungus fusarium graminearum. approximately one-third of the total srnas were produced from the gene region,and srnas with an antisense direction or 5′-u were involved in post-transcriptional gene regulation by reducing the stability of the corresponding gene transcripts. although both dicers and argonautes partially share their functions,the sex-specific rnai pathway is primarily mediated by fgdicer1 and fgago2,while the constitutively expressed rnai components fgdicer2 and fgago1 are responsible for hairpin-induced rnai. based on our results,we concluded that f. graminearum primarily utilizes ex-sirna-mediated rnai for ascosporogenesis but not for genome defenses and other developmental stages. each fungal species appears to have evolved rnai-based gene regulation for specific developmental stages or stress responses. this study provides new insights into the regulatory role of srnas in fungi and other lower eukaryotes. © 2017 son et al.