Concurrent expression of multiple insecticidal toxins as pyramided genes in the same host plant is one of the tangible strategies to delay the development of resistance in insects. In this study, an ideal combination of Insecticidal Cry Proteins (ICP) of Bacillus thuringiensis (Bt) viz., chimeric Cry1AcF (produced by domain swapping) and Cry2Aa (a synthetic protein with modified codon usage for plants) were selected. The main aim of this study was to determine whether the combination of two cry genes can confer better protection against Helicoverpa armigera over single a cry gene. Transgenic tobacco plants harbouring single and double ICP genes were generated and analysed for their insecticidal activity against cotton bollworm (H. armigera) through detached leaf insect bioassay. Efficacy studies showed that transgenic plants carrying the combinatorial construct had higher insecticidal activity compared to the individual genes and required lesser time for effective and maximum mortality of the pest. Molecular analysis and protein expression analysis of transgenic tobacco plants also correlated with the bioassay results. This study suggests that transgenic tobacco plants having both the toxins can be an effective option against H. armigera. However, the toxin combination should be carefully selected depending upon the most important pest species present in each geographical area.

中文翻译：

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两个密码子修饰的编码Bt杀虫蛋白Cry1AcF和Cry2Aa的基因的分子堆叠，用于控制棉铃虫的抗性发展

在同一宿主植物中同时表达多种杀虫毒素作为金字塔状基因，是延缓昆虫抗药性发展的切实策略之一。在这项研究中，选择了苏云金芽孢杆菌（Bt）的杀虫Cry蛋白（ICP），嵌合Cry1AcF（通过结构域交换产生）和Cry2Aa（植物修饰的密码子使用的合成蛋白）的理想组合。这项研究的主要目的是确定两个哭泣基因的组合是否比一次 哭泣能更好地保护棉铃虫基因。产生并针对棉铃虫（它们的杀虫活性分析转基因烟草植物携带单，双ICP基因ħ。棉铃虫通过离脱叶昆虫生物测定法）。功效研究表明，与单个基因相比，携带组合构建体的转基因植物具有更高的杀虫活性，并且需要更少的时间才能使害虫有效和最大程度地死亡。转基因烟草植物的分子分析和蛋白质表达分析也与生物测定结果相关。这项研究表明，含有两种毒素的转基因烟草植物可能是抗棉铃虫的有效选择。。但是，应根据每个地理区域中存在的最重要的有害生物种类仔细选择毒素组合。