BENT DNA IN THE LARGE INTERGENIC REGION OF WHEAT DWARF GEMINIVIRUS

Wheat dwarf virus (WDV) is a member of the geminivirus group, unique p lant DNA viruses which replicate exclusively via dsDNA replication int ermediates. The large intergenic region (LIR), a nontranscribed regula tory region, contains an inverted repeat with the potential to form a stem-loop structure in which the initiation site for WDV (+)strand (vi rion-sense) DNA replication has been mapped. In this work, we have stu died by two-dimensional electrophoresis and by electron microscopy the DNA structure of the WDV LIR and we have identified a DNA sequence wh ich confers a static DNA curvature. This is the first report of the oc currence of DNA bending in the regulatory region of a geminivirus geno me. The bending locus, defined by an 80-bp cluster of A(T) tracts, is located downstream from the potential stem-loop. The A(T) tract proxim al to the stem-loop structure is separated by 14 bp from the inverted repeat, and deletion of distal A(T) tracts abolished the curvature of the new WDV Delta LIR. The bending center maps similar to 80 bp downst ream from the putative initiation site for (+)strand DNA replication a nd similar to 70 bp upstream from the TATA box for virion-sense transc ription. The possible implications of the DNA bending locus as a regul atory element of WDV DNA replication and/or virion-sense transcription are discussed. (C) 1995 Academic Press, Inc.