A double-stranded RNA mycovirus in Botrytis cinerea

Area of Science:

• Mycology
• Virology
• Molecular Biology

Background:

• Botrytis cinerea is a significant plant pathogen.
• Extrachromosomal genetic elements, including double-stranded RNA (dsRNA), are known in some fungal species.
• The nature and association of these dsRNAs with viral particles in B. cinerea remain to be fully elucidated.

Purpose of the Study:

• To investigate the presence and characteristics of extrachromosomal genetic elements in the Botrytis cinerea CVg25 strain.
• To determine if these dsRNA molecules are associated with virus-like particles (VLPs).
• To identify which specific dsRNA molecules, if any, are encapsidated within VLPs.

Main Methods:

• Electron microscopy was used to visualize mycelium ultrathin sections and identify virus-like particles.
• Extrachromosomal genetic elements (dsRNAs) were extracted and characterized by molecular size (kb).
• Linear sucrose gradient centrifugation was employed to separate dsRNAs from mycelium-free extracts.
• Agarose-gel electrophoresis and electron microscopy were used to analyze fractions from the sucrose gradient.

Main Results:

• Three distinct dsRNA molecules, designated L (8.3 kb), M1 (2.0 kb), and M2 (1.4 kb), were detected in the B. cinerea CVg25 strain.
• Isometric virus-like particles approximately 40 nm in diameter were observed in mycelial sections.
• Sucrose gradient centrifugation revealed that only the L-dsRNA molecule copurified with the isometric virus-like particles.
• The morphology and size of the purified VLPs matched those observed in the mycelium.

Conclusions:

• The L-dsRNA molecule is likely encapsidated within isometric virus-like particles in the Botrytis cinerea CVg25 strain.
• The M1 and M2 dsRNA molecules do not appear to be encapsidated by these VLPs.
• These findings contribute to understanding the viral biology and genetic elements within Botrytis cinerea.