ORIGINAL PAPER Transgenic plants over-expressing insect-specific microRNA acquire insecticidal activity against Helicoverpa armigera: an alternative to Bt-toxin technology Aditi Agrawal . Vijayalakshmi Rajamani . Vanga Siva Reddy . Sunil Kumar Mukherjee . Raj K. Bhatnagar Received: 30 July 2014 / Accepted: 3 April 2015 Ó Springer International Publishing Switzerland 2015 Abstract The success of Bt transgenics in control- ling predation of crops has been tempered by sporadic emergence of resistance in targeted insect larvae. Such emerging threats have prompted the search for novel insecticidal molecules that are specific and could be expressed through plants. We have resorted to small RNA-based technology for an investigative search and focused our attention to an insect-specific miRNA that interferes with the insect molting process resulting in the death of the larvae. In this study, we report the designing of a vector that produces artificial mi- croRNA (amiR), namely amiR-24, which targets the chitinase gene of Helicoverpa armigera. This vector was used as transgene in tobacco. Northern blot and real-time analysis revealed the high level expression of amiR-24 in transgenic tobacco plants. Larvae feeding on the transgenic plants ceased to molt further and eventually died. Our results demonstrate that transgenic tobacco plants can express amiR-24 insec- tice specific to H. armigera. Keywords Artificial miRNA Á Agrobacterium Á Transgenic tobacco Á Insecticidal Á Insect bioassay Introduction Helicoverpa armigera (H. armigera) is one of the most damaging polyphagous pests of agricultural crops. In India, it infests at least 30 agricultural crops and causes substantial losses to legume, fiber, cereal, oilseed and vegetable crops. Various chemical pesti- cides have been used for decades to control this pest, but the adverse effects towards an eco-friendly approach make using chemical pesticides of growing concern. Bacillus thuringiensis (Bt) bacteria are used as biological pesticides which are environmentally safe and have been deemed as acceptable insecticides for more than 30 years (Tabashnik et al. 2009). The recent evolution of resistance against Bt is raising concern again and forcing the scientific community to look for some alternative strategies for durable pest control. Transgenic plants expressing small RNAs, targeting vital host functions, have revealed potentials for their development as alternatives to Bt application (Rajagopal et al. 2009; Ali et al. 2013). Transgenic plants expressing siRNA targeting insect cytochrome p-450 and GST have also offered substantial pest control (Mao et al. 2007). Electronic supplementary material The online version of this article (doi:10.1007/s11248-015-9880-x) contains supple- mentary material, which is available to authorized users. A. Agrawal Á V. Rajamani Á V. S. Reddy Á R. K. Bhatnagar (&) International Centre for Genetic Engineering and Biotechnology (ICGEB), Aruna Asaf Ali Marg, New Delhi 110067, India e-mail: raj@icgeb.res.in S. K. Mukherjee Department of Genetics, University of Delhi, New Delhi 110021, India 123 Transgenic Res DOI 10.1007/s11248-015-9880-x