A Satellite dsRNA Attenuates the Induction of Helper Virus-Mediated Symptoms in Aspergillus flavus

Abstract

Aspergillus flavus is an important fungal pathogen of animals and plants. Previously, we reported a novel partitivirus, Aspergillus flavus partitivirus 1 (AfPV1), infecting A. flavus. In this study, we obtained a small double-stranded (ds) RNA segment (734 bp), which is a satellite RNA of the helper virus, AfPV1. The presence of AfPV1 altered the colony morphology, decreased the number of conidiophores, created significantly larger vacuoles, and caused more sensitivity to osmotic, oxidative, and UV stresses in A. flavus, but the small RNA segment could attenuate the above symptoms caused by the helper virus AfPV1 in A. flavus. Moreover, AfPV1 infection reduced the pathogenicity of A. flavus in corn (Zea mays), honeycomb moth (Galleria mellonella), mice (Mus musculus), and the adhesion of conidia to host epithelial cells, and increased conidial death by macrophages. However, the small RNA segment could also attenuate the above symptoms caused by the helper virus AfPV1 in A. flavus, perhaps by reducing the genomic accumulation of the helper virus AfPV1 in A. flavus. We used this model to investigate transcriptional genes regulated by AfPV1 and the small RNA segment in A. flavus, and their role in generating different phenotypes. We found that the pathways of the genes regulated by AfPV1 in its host were similar to those of retroviral viruses. Therefore, some pathways may be of benefit to non-retroviral viral integration or endogenization into the genomes of its host. Moreover, some potential antiviral substances were also found in A. flavus using this system.

RNA interference of Aspergillus flavus in response to Aspergillus flavus partitivirus 1 infection

“…The functional AGOs of A. flavus needed further exploration. In a previous study, AfPV1 infection resulted in several large vacuoles in A. flavus cells ( Jiang et al, 2022 ). Here, we examined functions of sRNA affected by AfPV1 infection, and found that some GO terms and KEGG pathways are closely related to vacuole production in eukaryotic cells ( Figure 12 ), and support the previous finding that AfPV1 effects are related to vacuole formation in A. flavus cells.…”

“…However, mycovirus-mediated hypovirulence could be used as a new type of therapy for human pathogenic fungi (Kotta-Loizou and Coutts, 2017;van de Sande and Vonk, 2019). In the previous studies, our research group found that AfPV1 is placed as a new genus in Partitiviridae family, and AfPV1-infected A. flavus showed debilitation and hypovirulence in animal and insect studies (Jiang et al, 2019(Jiang et al, , 2022. However, the interactions between the AfPV1 and A. flavus are not well understood.…”

Experimental verification of strain-dependent relationship between mycovirus and its fungal host

“…In this regard, satellite RNA was most recently demonstrated to attenuate the phenotypic and transcriptomic effects of Aspergillus flavus partitivirus 1 infection in A. flavus . 48 Although the detailed molecular mechanism remains unknown, suppression machinery might also have been established in mycoviruses. To further understand the relationship between fungi and viruses, the mechanisms of such co-evolutionary relationships would be a focus in future studies.…”

AfuPmV-1-Infected Aspergillus fumigatus Is More Susceptible to Stress Than Virus-Free Fungus

“…In addition to Polymycoviridae, infection of A. fumigatus with a member of Chrysoviridae resulted in sensitivity to osmotic and oxidative stresses, but also impaired the host in the presence of formic acid and nitric oxide and under hypoxic low oxygen conditions [13]. In A. flavus, infection with a member of Partitiviridae also weakened the host against osmotic, oxidative, and ultraviolet stress [14].…”