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Phytophagous insect incidence is a serious threat for reduction of crop productivity globally. There is an estimation of one fourth of crop is being destroyed by insects annually. Indeed, the development of insectresistant crops is a great milestone in agriculture to increase crop yield and reduce pesticide dependency. Genetic engineering facilitates development of insect resistant crops by expressing bacterial d-endotoxins and vegetative insecticidal proteins and other plant genes like lectins, protease inhibitors, etc. In addition, RNA interference and genome editing through CRISPR Cas9 also provides new solutions for the development of insect-resistant crops. The resultant genetically modified crops showed resistance against lepidopteran, dipteran, homopteran and coleopteran insects. The insect-resistant crops have made a significant economic impact worldwide in terms of higher yield and low pesticide usage. In this review, we focus on different strategies for developing transgenics against insect pest control by expressing different insecticidal proteins in crops.

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Rice is a major cereal crop providing food and energy to more than half of world's population and drought is a challenging abiotic stress limiting rice production. Engineering drought tolerance trait is a major bottle neck because of multigenic control and complex nature. Two promising candidate genes utilized in engineering drought tolerance include DREB2A transcription factor (a master regulator of downstream stress inducible genes) and APX (an important ROS scavenging enzyme). Overexpression of DREB genes has shown encouraging results but with a negative impact on plant morphology and production. Moreover, co-expression of DREB2A and APX genes' influence on drought stress has not been studied. Hence, in the present study, overexpression of single genes DREB2A or APX and co-expression of these genes were studied for enhancement of drought tolerance in indica rice. Both genes under control of CaMV 35S promoter were transferred by Agrobacterium transformation into rice variety BPT5204 popular for slender grains in South India. Confirmation of T-DNA integration into rice genome was done with PCR analysis of transgenes. Homozygous transgenic lines of DREB2A, APX and DREB2A-APX generated in T 3 generation were evaluated for drought tolerance during seed germination, vegetative and reproductive stages. In seed germination stage, transgenic lines exhibited higher germination rates on 200 mM mannitol MS medium in comparison to WT. In vegetative stage, with-holding water for 7 days transgenic lines exhibited higher chlorophyll, proline, reducing sugars and enhanced activities of APX, SOD and catalase enzymes as well as reduced MDA content. The qRT-PCR analysis revealed higher relative transgene expression under drought stress. In reproductive stage, before maturity with-holding water for 7 days and restoring normal conditions, transgenic lines developed longer panicles and a higher number of grains/plant compared to WT. The overall results indicate that co-expression How to cite this paper: