Mycoreovirus genome rearrangements associated with RNA silencing deficiency

Area of Science:

• Mycology
• Virology
• Molecular Biology

Background:

• Mycoreovirus 1 (MyRV1) is a double-stranded RNA virus infecting the chestnut blight fungus Cryphonectria parasitica.
• MyRV1 confers hypovirulence, a reduced virulence phenotype.
• Viral protein p29, encoded by Cryphonectria hypovirus 1, is known to induce MyRV1 genome rearrangements and suppress RNA silencing.

Purpose of the Study:

• To investigate the role of the host RNA silencing pathway in suppressing MyRV1 genome rearrangements.
• To determine if defects in host RNA silencing components affect the frequency of MyRV1 genome rearrangements.

Main Methods:

• Utilized wild-type and mutant strains of MyRV1 and Cryphonectria parasitica.
• Employed host strains with deletions in RNA silencing genes (dicer-like [dcl] and argonaute-like [agl]).
• Infected host strains with a MyRV1 S4 internal deletion mutant (MyRV1/S4ss).

Main Results:

• Intragenic rearrangements, including duplication of segments S1, S2, and S3, occurred more frequently in RNA silencing-deficient host strains (Δdcl2 and Δagl2) infected with MyRV1/S4ss.
• Increased rearrangement frequency was specific to the MyRV1/S4ss and Δdcl2/Δagl2 strain combinations.
• Genome rearrangement generation required longer culture periods in Δagl2 compared to Δdcl2.

Conclusions:

• Host RNA silencing plays a suppressive role in preventing genome rearrangements of double-stranded RNA viruses like MyRV1.
• Specific interactions between viral and host genetic components influence the rate of viral genome instability.