The present invention relates to the field of plant genetic engineering for the purpose of developing transgenic plants improved for insect resistance. Particularly, the invention provides synthetic nucleotide sequence or a variant thereof engineered for high expression in plants, which encodes modified Cryl Ac pesticidal proteins. Said synthetic DNA sequence and variant thereof with SEQ ID No. 1 and 2 respectively is modified for having high transcription, high codon adaptation index, high GC content and optimized plant codons enabling efficient expression of the gene while the resultant protein possess increased in-vivo stability and processing and is highly efficacious against target pests. The modified crylAc gene (s) of the invention has been expressed in tobacco and cotton and bioefficacy of the plant expressed proteins against target insects is demonstrated.
