Scaled codon usage similarity index: A comprehensive resource for crop plants.

Over the past three decades species-specific codon usage bias has been used to optimize heterologous gene expression in the target host. However, synthesizing codon optimized gene for multiple species is not achievable due to the prohibitive expense of DNA synthesis. To address this challenge, grouping species with similar codon usage can reduce the need for species-specific codon optimised gene synthesis. We introduced Scaled Codon Usage Similarity (SCUS) index to standardize species similarity assessments based on codon usage profiles. By analysing the SCUS index of 77 plant nuclear genomes from 13 families, we identified codon usage patterns and similarities. We developed an online SCUS index database and a Consensus Relative Synonymous Codon Usage (CRSCU) calculator, available at https://pcud.plantcodon.info. The CRSCU calculator helps determine the most suitable codon usage pattern among two or more species. The SCUS index and CRSCU calculator will facilitate the development of multi-species expression systems, enabling the efficient expression of a single synthetic gene across various crop species. This innovation paves the way for cost-effective and efficient heterologous gene expression across diverse crop species.