Does the growth temperature of a prokaryote influence the purine content of its mRNAs?

The formation and breaking of hydrogen bonds between nucleic acid bases are dependent on temperature. The high G + C content of organisms was surmised to be an adaptation for high temperature survival because of the thermal stability of G:C pairs. However, a survey of genomic GC% and optimum growth temperature (OGT) of several prokaryotes revoked any direct relation between them. Significantly high purine (R = A or G) content in mRNAs is also seen as a selective response for survival among thermophiles. Nevertheless, the biological relevance of thermophiles loading their unstable mRNAs with excess purines (purine-loading or R-loading) is not persuasive. Here, we analysed the mRNA sequences from the genomes of 168 prokaryotes (as obtained from NCBI Genome database) with their OGTs ranging from − 5 °C to 100 °C to verify the relation between R-loading and OGT. Our analysis fails to demonstrate any correlation between R-loading of the mRNA pool and OGT of a prokaryote. The percentage of purine-loaded mRNAs in prokaryotes is found to be in a rough negative correlation with the genomic GC% (r2 = 0.655, slope = − 1.478, P < 000.1). We conclude that genomic GC% and bias against certain combinations of nucleotides drive the mRNA-synonymous (sense) strands of DNA towards variations in R-loading.

► An updated analysis of 168 prokaryotic mRNA pools for purine-loading. ► No correlation between purine-loading and OGT of prokaryotes. ► Dataset of 53 mesophiles (OGT = 37 °C) show nearly all patterns of purine-loading. ► Genomic GC% in a negative correlation with the percentage of purine-loaded mRNAs. ► GC%, YY dimers and G-rich tracts drive mRNAs towards variations in R-loading.