Revelation of core promoter elements and bidirectional regulation of Geminivirus genes in Escherichia coli

Several geminiviruses have been show to possess cross-kingdom gene expression capability. In addition, the intergenic region (IR) of geminivirus genomes is known to regulate the transcription of viral early genes (complementary-sense, C-sense) and late genes (virion-sense, V-sense) located in opposite directions in viral genomic DNAs. However, the underlying mechanism remained elusive. In this study, the transcriptional regulation activities in the IR of ageratum yellow vein virus isolate NT (AYVV-NT), a monopartite geminivirus, were characterized in Escherichia coli, by using a promoter-trapping system. A functional bidirectional promoter core and regulatory elements for C- and V-sense genes were identified in the IR of AYVV-NT. Quantitative analyses revealed differences in promoter activity in various E. coli strains, suggesting that promoter regulation is strain-dependent and influenced by bacterial transcription factors. These findings provide insights into how plant-infecting geminiviruses may regulate gene expression in prokaryotic environments and highlight the potential applications of such viral regulatory elements in bacterial expression systems.