This study aimed to demonstrate the existence of antiviral RNA silencing mechanisms in Sclerotinia sclerotiorum by probing wild-type and RNA-silencing-deficient strains of the fungus with an RNA virus and a circular DNA virus. Key silencing-related genes, specifically dicers, were disrupted in order to dissect the RNA silencing pathway and provide useful information on fungal control. Dicers Dcl-1, Dcl-2, and both Dcl-1/Dcl-2- genes were displaced by selective marker(s). Disruption mutants were then compared for changes in phenotype, virulence, susceptibility to viral infection, and small RNA accumulation compared to the wild-type strain. Disruption of Dcl-1 or Dcl-2 resulted in no changes in phenotype compared to wild-type S. sclerotiorum; however, the double dicer mutant strain exhibited slower growth. To examine the effect of viral infection on strains containing null-mutations of Dcl-1, Dcl-2 or both genes, mutants were transfected with full-length RNA transcripts of a hypovirus SsHV2L and copies of a single-stranded DNA mycovirus- SsHADV-1 as a synthetic virus. Results indicate that the ΔDcl-1/Dcl-2 double mutant which was slow growing without virus infection exhibited much more severe debilitation following virus infection. Altered colony morphology including: reduced pigmentation, significantly slower growth, and delayed sclerotial formation. Additionally, there is an absence of virus-derived small RNAs in the virus-infected ∆Dcl-1/Dcl-2 mutant compared to the virus-infected wild-type strain which displays a high percentage of virus-derived small RNA. The findings of these studies suggest that if both dicers are silenced, invasive nucleic acids which include mycoviruses ubiquitous in nature- can greatly debilitate the virulence of fungal plant pathogens.

Mosquitoes are widespread arthropods that serve as vectors for a broad spectrum of viruses, many of which pose a substantial threat to humans. Conversely, some viruses may seemingly present with beneficial implications for the health of man whilst impinging on other domains of life, such as the fungi-infecting mycoviruses. This study is only the second one so far to describe the exceptionally scarcely identified Xanthi chryso-like virus (XCLV), member of the mycopathogenic Chrysoviridae family, in a new geographical area and a novel potential arthropod vector, the Culex pipiens mosquito. Interestingly, the XCLV was initially fortuitously detected by West Nile virus-specific primers directed at a conserved part of the NS5 gene, possibly indicative of a genetic resemblance and shared ancestry reflected in the NS5 evolutionary heritage. Detection and characterization of the virus and insect alike was done via PCR and Sanger sequencing. This investigation draws attention to our knowledge of viral pervasiveness – be it topographical or vectorial – and how humble it truly is. Additionally, we would propose that more attention be given to arthropod-borne viral pathogens that might prove advantageous to human health.

RNA-viruses of the genera Ambivirus, Mitovirus, Sclerotimonavirus, and Partitivirus were found in a single isolate of Fusarium graminearum. The genomes of the mitovirus, sclerotimonavirus, and partitivirus were assigned to previously described viruses, whereas the ambivirus genome putatively represents a new species, named Fusarium graminearum ambivirus 1 (FgAV1). To investigate the effect of mycoviruses on the fungal phenotype, spontaneous loss of mycoviruses during meiosis and transmission of mycoviruses into a new strain by anastomosis were used to obtain isogenic F. graminearum strains with and without mycoviruses. Notable effects observed in mycovirus-harboring strains were (i) suppression of the synthesis of trichothecene mycotoxins and their precursor trichodiene, (ii) suppression of the synthesis of the defense compound aurofusarin, (iii) stimulation of the emission of 2-methyl-1-butanol and 3-methyl-1-butanol, and (iv) increased attractiveness of fungal mycelia for fungivorous collembolans. Increased attractiveness of mycovirus-infected filamentous fungi to animal predators opens new perspectives on the ecological implications of infection of fungi with viruses.

Acute leukemias constitute some of the most common malignant disorders. Despite significant progress made in the treatment of these disorders, their etiology remains unknown. A large and diverse group of genetic and environmental variables have been proposed. The role of a variety of factors, including pre-existing and acquired genetic mutations, exposure to radiation and various chemicals during pre-conception, pregnancy and throughout life have been explored. The effects of inherited genetic variations and disorders, pre-existing diseases, infectious agents, hobbies, occupations, prior treatments and a host of other factors have been proposed, but none is universally applicable to all cases. Variation in the incidence and prognosis based on the age, sex, race, type of the disease, geographic area of residence and other factors are intriguing, but remains unexplained. Advances in genomic profiling, including genome‐wide gene expression, DNA copy number, and single nucleotide polymorphism [SNP] genotype may shed some light on the role of genetics in these disparities. Separate two-hit hypothesis for the development of acute myeloblastic and lymphoblastic leukemia have been proposed. The latter combines genetics and infection factors resulting in leukemogenesis. A number of pre- and post-natal environmental conditions and exposure to infections, including a mycovirus infected Aspergillus flavus, have been suggested. The exact nature, timing, sequence of the events and mechanisms resulting in occurrence of leukemia requires further investigations. This review summarizes some of the above factors and the direction for future research on the etiology of acute leukemias.