Microbiology Spectrum (Dec 2023)

A novel botybirnavirus with a unique satellite dsRNA causes latent infection in Didymella theifolia isolated from tea plants

  • Liangchao Ye,
  • Xinyu Shi,
  • Yunqiang He,
  • Jiao Chen,
  • Qingeng Xu,
  • Karim Shafik,
  • Lanning Fu,
  • Yumeng Yin,
  • Ioly Kotta-Loizou,
  • Wenxing Xu

DOI
https://doi.org/10.1128/spectrum.00033-23
Journal volume & issue
Vol. 11, no. 6

Abstract

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ABSTRACT The unique, recently discovered fungus Didymella theifolia specifically infects local varieties of tea plant Camellia sinensis in China, and therefore, the characterization of its mycoviruses is important. Three double-stranded (ds) RNAs (1, 2, and 3, with 6,338, 5,910, and 727 bp in size, respectively) were identified in the avirulent D. theifolia strain CJP4-1, which exhibits normal growth and morphology. Characterization of these double-stranded RNAs (dsRNAs) revealed that the two largest elements are the genomic components of a novel botybirnavirus, tentatively named Didymella theifolia botybirnavirus 1 (DtBRV1). Conversely, dsRNA3 shares no detectable similarity with sequences deposited in public databases but has high similarity with the 5′-terminal regions of dsRNAs 1 and 2 and contains a duplicated region encoding a putative small peptide. All three dsRNAs are encapsidated in isometric virions ca. 40 nm in diameter, supporting the notion that dsRNA3 is a DtBRV1 satellite. SDS-polyacrylamide gel electrophoresis in combination with peptide mass fingerprint analysis revealed that the DtBRV1 capsid protein consists of polypeptides encoded by the 5′-terminal regions of both genomic components dsRNA1 and dsRNA2. Vertical transmission of DtBRV1 through conidia is efficient, while its horizontal transmission from CJP4-1 to other strains was not detected. DtBRV1, with or without dsRNA3, has no obvious effects on fungal growth and virulence, as illustrated following transfection of the virulent D. theifolia strain JYC1-6. In summary, DtBRV1 exhibits unique molecular traits and contributes to our understanding of mycovirus diversity. IMPORTANCE A novel botybirnavirus, infecting the tea plant pathogen Didymella theifolia and tentatively named Didymella theifolia botybirnavirus 1 (DtBRV1), together with an additional double-stranded RNA (dsRNA), was characterized. DtBRV1 comprises two dsRNAs (1 and 2) encapsidated in isometric virions, while dsRNA3 is a satellite. The satellite represents a unique specimen since it contains a duplicated region and has high similarity to the two botybirnavirus dsRNAs, supporting the notion that it most likely originated from a deficient genomic component. The biological characteristics of DtBRV1 were further determined. With their unique molecular traits, DtBRV1 and its related dsRNA expand our understanding of virus diversity, taxonomy, and evolution.

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