In order to develop intrinsic resistance, genes from various sources have been cloned and expressed in plants but in most cases, the transgene failed to produce desired quantity of foreign protein in the heterologous system. Codon optimization is a general approach for improving expression of gene in any heterologous system. Full length chiA (1692 bp) from S. marcescens 141 (sm141chiA) was considered for removal of regulatory signals (partial optimized- sm141chiApm) and replacement of rare codons with preferred codons by tobacco (fully optimized- sm141chiAfm). Of 1692 bp, 22 and 432...