MYMIV-AC2, a Geminiviral RNAi Suppressor Protein, Has Potential to Increase the Transgene Expression Jamilur Rahman & Sumona Karjee & Sunil Kumar Mukherjee Received: 12 September 2011 / Accepted: 23 April 2012 / Published online: 17 May 2012 # Springer Science+Business Media, LLC 2012 Abstract Gene silencing is one of the limiting factors for transgene expression in plants. But the plant viruses have learnt to suppress gene silencing by encoding the protein(s), called RNA silencing suppressor(s) (RSS). Hence, these proteins could be used to overcome the limitation for transgene expression. The RNAi suppressors, namely HC-Pro and P19, have been shown to enhance the transgene expression but other RSS proteins have not been screened for similar role. Moreover, none of RSSs from the DNA viruses are known for enhancing the expression of transgenes. The Mungbean Yellow Mosaic India Virus (MYMIV) belonging to the genus Begomovirus within the family of Geminiviridae encodes an RSS called the AC2 protein. Here, we used AC2 to elevate the expression of the transgenes. Upon introduction of MYMIV-AC2 in the silenced GFP transgenic tobacco lines, by either genetic hybridisation or transgenesis, the GFP expression was enhanced several fold in F1 and T0 lines. The GFP-siRNA levels were much reduced in F1 and T0 lines compared with those of the initial parental silenced lines. The enhanced GFP expres- sion was also observed at the cellular level. This approach was also successful in enhancing the expression of another transgene, namely topoisomeraseII. Keywords RNAi . Viral suppressor . Post-transcriptional gene silencing . Molecular farming . Transgene expression List of abbreviations GM Genetically modified PTGS Post-translational gene silencing TGS Transcriptional gene silencing RNAi RNA interference Appl Biochem Biotechnol (2012) 167:758–775 DOI 10.1007/s12010-012-9702-z Electronic supplementary material The online version of this article (doi:10.1007/s12010-012-9702-z) contains supplementary material, which is available to authorized users. J. Rahman : S. Karjee : S. K. Mukherjee (*) Plant Molecular Biology Group, International Centre for Genetic Engineering and Biotechnology (ICGEB), Aruna Asaf Ali Marg, New Delhi 110067, India e-mail: sunilm@icgeb.res.in URL: http://www.icgeb.org/plant-biology-plant-molecular-biology.html