Impact of codon optimization on gene expression and insecticidal efficacy in maize.

Introduction: Codon optimization is critical for high expression of foreign genes in heterologous systems. The gene from is a promising candidate for controlling .

Methods And Results: To develop insect-resistant maize, we designed two codon-optimized variants ( and ) based on maize codon usage bias. Both recombinant proteins expressed in exhibited high insecticidal activity. However, in transgenic maize, Vip3Aa11-m1 exhibited strong insecticidal activity against and , while Vip3Aa11-m2 lost activity despite identical amino acid sequences. RT-PCR analysis confirmed that both genes were transcribed correctly, but western blot results demonstrated a smaller product for , suggesting a translation-level alteration. Segment replacement and point mutation experiments in maize protoplasts demonstrated that the synonymous codon AAT (Asn) at the fourth amino acid position in was associated with the production of a truncated protein, suggesting that the AAT codon may influence the selection of the translation initiation site, potentially shifting it to a downstream ATG (Met) codon.

Discussion: These findings not only reveal the critical role of codon context in translation initiation and protein integrity but also provide a novel strategy for optimizing foreign genes in crop improvement, particularly offering valuable insights for engineering insect-resistant maize using Bt genes.