Complete Genome Sequence of the First Chrysovirus From the Phytopathogenic Fungus Alternaria Solani on Potato in China

The full genome of a double-stranded RNA (dsRNA) mycovirus, which was isolated from Alternaria solani strain DT-10 causing potato foliar disease and designated as Alternaria solani chrysovirus 1 (AsCV1), consisted of four dsRNA segments (dsRNA 1–4) with the length of 3600 bp, 3128 bp, 2996 bp, and 2714 bp, respectively. RNA-dependent RNA polymerase (RdRp, 1084 amino acids (aa)), putative capsid protein (905 aa), Alphachryso-P3 (835 aa), and Alphachryso-P4 (729 aa) were encoded by dsRNA1, dsRNA2, dsRNA3, and dsRNA4, respectively, which had the highest identities of 41.77%-72.38% to the counterparts of Helminthosporium victoriae virus 145S (HvV145S) in the genus Alphachrysovirus of the family Chrysoviridae. Moreover, the 5′-untranslated regions (UTRs) with several unique inserts (3–37 bp) and deletions (5–64 bp) of AsCV1 dsRNA 1–4 shared 51.65%-68.01% identities to those of HvV145S. Phylogenetic analysis of RdRp suggested that AsCV1 clustered the most closely with HvV145S. Based on the characteristics of distinct host, low identities of encoded proteins, special traits in 5′-UTRs of dsRNA 1–4, and phylogenetic analysis of RdRp, AsCV1 was confirmed to be a new species in the genus Alphachrysovirus. To our best knowledge, this is the first alphachrysovirus identified from phytopathogenic A. solani.

My Life and Virus Research Journey

My long career in virology has been a continuous learning exercise with a very modest start. Virology and related pertinent fields have changed significantly during my lifetime. Sometimes I wish that my career had just started and I could apply all available and state of the art technology to solving problems and explaining intriguing observations. I was always convinced that visiting growers’ fields is essential for researchers to get firsthand observations and knowledge of virus disease problems under field conditions. I never thought I would pursue so many avenues of research, yet it is true that research never ends. I enjoyed dissecting strain diversity in a very important plant pathogen like bean pod mottle virus (BPMV) and using BPMV-based vectors to address fundamental virology questions. Lastly, solving the enigma of the transmissible disease of Helminthosporium victoriae and attempting to gain an understanding of the molecular basis of disease in a plant pathogenic fungus were thrilling.

Electron Cryo-Microscopy studies of Helminthosporium victoriae Virus 190S

Extended abstract of a paper presented at Microscopy and Microanalysis 2011 in Nashville, Tennessee, USA, August 7–August 11, 2011.

Disease Phenotype of Virus-Infected Helminthosporium victoriae Is Independent of Overexpression of the Cellular Alcohol Oxidase/RNA-Binding Protein Hv-p68

The cellular protein Hv-p68 is a novel alcohol oxidase/RNA-binding protein that is overexpressed in virus-infected isolates of the plant-pathogenic fungus Helminthosporium victoriae (teleomorph: Cochliobolus victoriae). Overproduction of Hv-p68 has been hypothesized to lead to the accumulation of toxic aldehydes and to induce the disease phenotype associated with the virus-infected isolates. We overexpressed the Hv-p68 gene in virus-free isolates and evaluated the morphology of the resulting colonies. We cloned and sequenced the Hv-p68 genomic DNA, which contains five introns and the complete Hv-p68 coding sequence. Vectors for overexpression of the Hv-p68 gene were constructed with either Hv-p68 cDNA or the intron-containing Hv-p68 genomic DNA. Expression of Hv-p68 was significantly higher if the genomic sequence was used for transformation than if the cDNA sequence was used. The virus-free fungal transformants that overexpressed Hv-p68 gene did not exhibit the disease phenotype. In contrast, these transformants showed enhanced growth rates when compared with the nontransformed and empty vector controls. Interestingly, overexpression of Hv-p68 in a fungal isolate infected with both the totivirus Helminthosporium victoriae 190S virus (Hv190SV) and the chrysovirus Helminthosporium victoriae 145S virus (Hv145S) showed enhanced accumulation of the Hv145SV double-stranded (ds)RNA, but not of the Hv190SV. These results are consistent with an earlier report that Hv-p68 co-purified with viral dsRNA, mainly that of the Hv145SV. Elucidation of the role of Hv-p68 in disease induction is important for an understanding of host-virus interactions in this fungus-virus system.