Cucumber green mottle mosaic virus encodes additional small proteins with specific subcellular localizations and...

Area of Science:

• Virology
• Molecular Biology
• Plant Pathology

Background:

• Positive-sense single-stranded RNA (+ssRNA) viruses, including destructive tobamoviruses, are traditionally thought to encode proteins only on their positive RNA strand.
• Understanding the full coding capacity of viruses is essential for developing effective control strategies against plant diseases threatening global food security.

Purpose of the Study:

• To investigate the existence and function of potential coding regions on the negative strand of tobamoviruses.
• To determine the role of these novel genes in viral virulence and host-pathogen interactions.

Main Methods:

• Identification of reverse open-reading frames (rORFs) in the negative strand of tobamoviruses.
• Mass spectrometry and ribosome profiling to detect rORF-encoded peptides and confirm translation.
• Site-directed mutagenesis to assess the impact of rORFs on viral virulence and pathogenicity.

Main Results:

• Novel rORFs were identified and confirmed to be translated, expanding the known tobamoviral proteome.
• Mutations in rORF1 and rORF2 significantly reduced cucumber green mottle mosaic virus (CGMMV) virulence, which was rescued by ectopic expression.
• rORF1 interacts with the viral 126-kD protein in peroxisomes, and PEX3 mediates rORF1 targeting to these organelles.

Conclusions:

• Tobamoviruses possess a larger proteome than previously recognized, with functional genes encoded on the negative RNA strand.
• Peroxisomes are identified as critical host compartments for viral replication and virulence, representing novel targets for therapeutic intervention.
• The discovery of rORFs and their functional significance provides new insights into tobamovirus infectivity and pathogenesis.