Protein abundances are more conserved than mRNA abundances across diverse taxa

Proteins play major roles in most biological processes as a consequence protein expression levels are highly regulated While extensive post transcriptional translational and protein degradation control clearly influence protein concentration and functionality it is often thought that protein abundances are primarily determined by the abundances of the corresponding mRNAs Hence surprisingly a recent study showed that abundances of orthologous nematode and fly proteins correlate better than their corresponding mRNA abundances We tested if this phenomenon is general by collecting and testing matching large scale protein and mRNA expression data sets from seven different species two bacteria yeast nematode fly human and rice We find that steady state abundances of proteins show significantly higher correlation across these diverse phylogenetic taxa than the abundances of their corresponding mRNAs (p = 0 0008 paired Wilcoxon) These data support the presence of strong selective pressure to maintain protein abundances during evolution even when mRNA abundances diverge