Recombination between viral RNA and transgenic plant transcripts

Area of Science:

• Plant virology
• Molecular biology
• Genetics

Background:

• Cowpea chlorotic mottle virus (CCMV) requires a functional capsid gene for systemic infection.
• Transgenic plants can express viral genes, potentially influencing viral replication and spread.
• CCMV deletion mutants lacking essential gene segments may rely on host or external factors for complementation.

Purpose of the Study:

• To investigate if transgenic expression of a partial CCMV capsid gene can complement a deletion mutant lacking the 3' one-third of the gene.
• To determine the role of RNA recombination in restoring systemic infection by the CCMV deletion mutant in transgenic plants.
• To analyze the mechanism of viral RNA restoration through homologous recombination.

Main Methods:

• Generation of transgenic plants expressing the 3' two-thirds of the CCMV capsid gene.
• Inoculation of transgenic plants with a CCMV deletion mutant lacking the 3' one-third of the capsid gene.
• Analysis of viral RNA from infected plants to confirm systemic spread and identify recombination events.

Main Results:

• The CCMV deletion mutant replicated in inoculated cells of transgenic plants.
• Systemic infection was observed in a small proportion (4/125) of inoculated transgenic plants.
• Analysis confirmed RNA recombination had occurred, uniting the transgenic RNA and the challenge virus via aberrant homologous recombination.

Conclusions:

• A functional CCMV capsid gene is essential for systemic infection.
• RNA recombination can restore a functional capsid gene by uniting transgenic RNA with the challenge virus.
• Aberrant homologous recombination is a mechanism for restoring infectivity in defective RNA viruses within specific host contexts.