Deciphering the role of codon usage bias on gene expression and pathogen colonization in Crocus sativus

Abstract

Abstract Codon usage bias (CUB) is a ubiquitous phenomenon perseveres in genome of all the organisms. It impinges the gene expression and other genetic intricacies within a genome. The present study explicates the pattern of codon usage in the protein coding sequence of Crocus sativus and its relation with gene expression. Gene expression analysis in C. sativus showed genes with high expression had a preference of G base at third position. CUB had an inverse relation with gene expression. Coding sequences with ENC < 50 had low FPKM value while low codon bias group (ENC > 50) possessed high FPKM value. The low tAI values showed the low translation efficiency of genes in C. sativus. The non-significant MELP and ENC correlation analysis suggested that expression of genes might not be associated with CUB. ENC and PR-2 plot revealed mutation pressure and natural selection played role in shaping CUB. However, neutrality plot conclusively depicted the dominance of natural selection in regulating the configuration of codons in all three species. In addition, the role of CUB regarding the predilection of fungal pathogens Aspergillus fumigatus and Fusarium oxysporum towards host plant C. sativus has also been expounded. We found a similar trend of codon usage pattern operative in plant and fungal pathogens as both the fungal pathogens and host plant showed similar GC rich genomic content as well as preference for GC ending codons at third codon position. This concurrence might be attributed for the colonization of fungal pathogens in C. sativus. Overall, different CUB indices reflected a weak codon bias in the C. sativus, F. oxysporum and A. fumigatus genome.