Comparative genome-wide analysis of extracellular small RNAs from the mucormycosis pathogen Rhizopus delemar

Rhizopus delemar is an emerging fungal pathogen causing devastating mucormycosis in immunocompromised individuals. The organism remains understudied and there are urgent needs for new methods of rapid disease diagnosis for timely therapy. Extracellular vesicles with encapsulated RNAs have recently been discovered to have great potential applications for disease diagnoses and treatments. To explore the utilization of ex-RNA in studies of mucormycosis, we have performed RNA-Seq of ex-sRNAs from two clinical strains of R. delemar. Approximately 3.3 and 3.2 million clean reads were obtained from FGSC-9543 and CDC-8219 strains, respectively. The median sequence length of the sRNAs was 22 nts, with a minimum of 18 and a maximum of 30 nts. Further annotation identified 560 and 526 miRNAs from FGSC-9543 and CDC-8219 strains, respectively. miRNA target prediction and analysis of GO and KEGG pathways have revealed that the regulation of metabolism, secondary metabolite biosynthesis, and two-component system signaling are important during growth. We have also validated RNA-Seq by qRT-PCR and Northern blotting analysis of randomly selected miRNAs. Our results show that R. delemar has a rich reservoir of secreted ex-sRNAs and our studies could facilitate the development of improved diagnostic methods as well as elucidating virulence mechanisms for R. delemar infection.