Replication promiscuity of DNA-b satellites associated with monopartite begomoviruses; deletion mutagenesis of the Ageratum yellow vein virus DNA-b satellite localizes sequences involved in replication

Received 28 May 2008 Accepted 21 August 2008 Pseudorecombination studies in Nicotiana benthamiana demonstrate that Ageratum yellow vein virus (AYVV) and Eupatorium yellow vein virus (EpYVV) can functionally interact with DNA-b satellites associated with AYVV, EpYVV, cotton leaf curl Multan virus (CLCuMV) and honeysuckle yellow vein virus (HYVV). In contrast, CLCuMV shows some specificity in its ability to interact with distinct satellites and HYVV is able to interact only with its own satellite. Using an N. benthamiana leaf disk assay, we have demonstrated that HYVV is unable to trans-replicate other satellites. To investigate the basis of trans-replication compatibility, deletion mutagenesis of AYVV DNA-b has been used to localize the origin of replication to approximately 360 nt, encompassing the ubiquitous nonanucleotide/stem–loop structure, satellite conserved region (SCR) and part of the intergenic region immediately upstream of the SCR. Additional deletions within this intergenic region have identified a region that is essential for replication. The capacity for DNA-b satellites to functionally interact with distinct geminivirus species and its implications for disease diversification are discussed.