DNA bending as a potential regulatory cis - acting element of the geminivirus intergenic region

infect, among others, wheat (wheat dwarf virus, WDV), maize (maize streak virus, MSV) or different species of grasses. We are interested in identifying regions within the control region of the geminivirus genome which may act as regulatory elements during viral DNA replication and/or transcription. Recently, we have studied the DNA structure of the WDV large intergenic region by 2-dimensional polyacrylamide gel electrophoresis and by electron microscopy, and we have characterized a previously unidentified DNA sequence which confers intrinsic DNA bending properties. Here, we extend this study to other members of the subgroup I (SI) geminiviruses, in particular MSV. In general, DNA curvature was conferred by the presence of A-tracts separated by an integral number of helical turns. DNA bending within the regulatory regions of Sl geminivirus DNA appears to be a common, though not general, situation. The possible implications of DNA bending of WDV as well as other Sl geminivirus DNA as a regulatory element of viral DNA replication and/or transcription will be discussed in relation to the known effects of DNA curvature in other prokaryotic and eukaryotic replicons.