A novel ilarvirus protein CP-RT is expressed via stop codon readthrough and suppresses RDR6-dependent RNA silencing

Area of Science:

• Plant virology
• Molecular biology
• RNA virus research

Background:

• Ilarviruses are significant plant RNA viruses, some causing crop diseases.
• Their genome structure includes RNA segments encoding key viral proteins.
• A protein that suppresses RNA silencing is present in some ilarvirus subgroups.

Purpose of the Study:

• To investigate the function of a newly identified protein, CP-RT, in ilarviruses.
• To determine the role of CP-RT in viral infection and spread within plants.
• To explore the mechanism of CP-RT's function and its importance for persistent infections.

Main Methods:

• Analysis of RNA3 from various ilarviruses to identify the CP-RT coding sequence.
• Expression studies of CP-RT in planta using asparagus virus 2 as a model.
• Functional assays to assess CP-RT's RNA silencing suppression activity.
• Mutational analysis of the zinc-finger motif within the RT domain.
• Cross-subgroup complementation experiments.

Main Results:

• RNA3 in many ilarviruses encodes an additional protein (CP-RT) via ribosomal readthrough.
• CP-RT is expressed in planta and acts as a weak suppressor of RNA silencing.
• CP-RT is essential for persistent systemic infection in leaves and the shoot apical meristem.
• A putative zinc-finger motif in the RT domain is critical for CP-RT function.
• Cross-subgroup complementation demonstrates conserved function of RT proteins.

Conclusions:

• Ilarviruses utilize CP-RT for persistent infections by suppressing host RNA silencing.
• CP-RT plays a vital role in meristem invasion and potentially vertical transmission.
• The findings provide new insights into ilarvirus biology and host-pathogen interactions.