intact RBR-binding motif is not required for infectivity of Maize streak virus in cereals, but is required for invasion of mesophyll cells

• Published in: Journal of general virology Vol. 86; no. 3; pp. 797 - 801
• Main Authors: McGivern, D.R, Findlay, K.C, Montague, N.P, Boulton, M.I
• Format: Journal Article
• Language: English
• Published: Reading Soc General Microbiol 01.03.2005; Society for General Microbiology
• Subjects: Binding Sites; Biological and medical sciences; cell invasion; cell suspension culture; corn; Fabaceae - virology; Fundamental and applied biological sciences. Psychology; infection; Maize streak virus; Maize streak virus - isolation & purification; Maize streak virus - metabolism; Maize streak virus - physiology; mesophyll; Microbiology; Miscellaneous; pathogenesis; Plant Leaves - virology; Protein Binding; replication-associated protein; Retinoblastoma Protein - metabolism; retinoblastoma-related protein; viral proteins; Viral Proteins - metabolism; Virology; Virus Replication; Zea mays; Zea mays - virology; Virus; Plant pathogen; Microbiology; Maize streak virus; Mastrevirus; Infectivity; Geminiviridae; Virology
• ISSN: 0022-1317; 1465-2099
• DOI: 10.1099/vir.0.80689-0

The replication-associated protein (RepA) of Maize streak virus interacts in yeast with retinoblastoma-related protein (RBR), the negative regulator of cell-cycle progression. This may allow geminiviruses to subvert cell-cycle control to provide an environment that is suitable for viral DNA replication. To determine the importance of this interaction for MSV infection, the RBR-binding motif, LxCxE, was mutated to IxCxE or LxCxK. Whilst RBR binding in yeast could not be detected for the LxCxK mutant, the IxCxE protein retained limited binding activity. Both mutants were able to replicate in maize cultures and to infect maize plants. However, whereas the wild-type virus invaded mesophyll cells of mature leaves, the LxCxK mutant was restricted to the vasculature, which is invaded prior to leaf maturity. Mature leaves contain high levels of RBR and it is suggested that the MSV RepA-RBR interaction is essential only in tissues with high levels of active RBR.