A coat-independent superinfection exclusion rapidly imposed in Nicotiana benthamiana cells by tobacco mosaic virus is not prevented by depletion of the movement protein

• DOI: 10.1007/s11103-013-0028-1
• Publication Date: 2013-02-18T15:52:05Z
• Authors: José Manuel Julve; Antoni Gandía; Asun Fernández-de...; Alejandro Sarrion...; Bas Castelijns; Antonio Granell; Diego Orzaez
• Keywords: Nicotiana; Time Factors; Genes, Viral; Genetic Vectors; Green Fluorescent Proteins; Superinfection exclusion; 03 medical and health sciences; Plant Cells; Viral Interference; BIOQUIMICA Y BIOLOGIA MOLECULAR; Cloning, Molecular; Plant Diseases; 0303 health sciences; Agroinfiltration; MICROBIOLOGIA; 3. Good health; Plant Leaves; Tobacco Mosaic Virus; Luminescent Proteins; Protein Transport; Agrobacterium tumefaciens; Tobacco mosaic virus; Homologous interference; Capsid Proteins; Red Fluorescent Protein

New evidence is emerging which indicates that population variants in plant virus infections are not uniformly distributed along the plant, but structured in a mosaic-like pattern due to limitation to the superinfection imposed by resident viral clones. The mechanisms that prevent the infection of a challenge virus into a previously infected cell, a phenomenon known as superinfection exclusion (SE) or Homologous Interference, are only partially understood. By taking advantage of a deconstructed tobacco mosaic virus (TMV) system, where the capsid protein (CP) gene is replaced by fluorescent proteins, an exclusion mechanism independent of CP was unveiled. Time-course superinfection experiments provided insights into SE dynamics. Initial infection levels affecting less than 10 % of cells led to full immunization in only 48 h, and measurable immunization levels were detected as early as 6 h post-primary infection. Depletion of a functional movement protein (MP) was also seen to slow down, but not to prevent, the SE mechanism. These observations suggest a CP-independent mechanism based on competition for a host-limiting factor, which operates at very low virus concentration. The possible involvement of host factors in SE has interesting implications as it would enable the host to influence the process.