Isolation and identification of promoter elements of Cotton leaf curl Multan betasatellite associated with Tomato leaf curl viruses

Betasatellite DNAs associated with Old World monopartite begomoviruses encode a single gene (βC1) which mediate the vital functions required for viral pathogenicity. A region of upstream translation start site of βC1 of Cotton leaf curl Multan betasatellite (CLCuMB) associated with Tomato leaf curl New Delhi virus was tested for its promoter activity. Transcript mapping studies revealed that the transcript had a very short leader sequence of 12?nt and 3′ end was 9 nt downstream of stop codon at 186?nt coordinate position. Transient expression studies in Nicotiana benthamiana using the β-glucuronidase reporter gene driven by a βC1 promoter of CLCuMB identified a 169?nt region (between 720 and 869?nt coordinate) upstream of βC1 which is important for βC1 transcription. Histochemical GUS staining of selected solanaceous hosts indicated that βC1 promoter was active in leaves of N. benthamiana and Nicotiana tabacum and leaves and fruit of tomato. Temporal regulation studies on viral transcript using semi-quantitative PCR showed that the βC1 is a late phase gene and is expressed only 48?h post-inoculation.