Their functionality is currently still debated because of their low level of expression and conservation between species.
In our results, we also observe the highest correlation between expression context conservation and sequence identity for the 1-1 ofthologS.of S. cerevisiae and C. elegans, rather than for two closer related Metazoa.
Table 3 presents the correlation coefficients between expression context conservation and sequence identity of the 1-1 orthologs for all species pairs.
In this analysis of the relationship between expression context conservation and sequence identity across orthologous groups, we conclude that the evolution rate of the gene sequence does not depend on its expression context.
We found significant negative relationships between SNP frequency and overall levels of gene expression, consistent with the commonly reported relationship between gene expression and gene conservation [ 73, 74].
In order to understand the relationship between expression level and expression conservation, we determined the conservation of sense-antisense pairs, by comparing the variation of expression between the two species S. cerevisiae and S. paradoxus in mid-log condition or other culture condition.
The two contrasting types of DE genes provide possible explanations for the previous controversial conclusions about the relationships between molecular evolution and expression evolution of genes in different species, and the relationship between expression breadth and expression conservation in evolution.
Given this precedent, the correlation between pattern of expression and evolutionary conservation and emergence of duplicates in two model plant species, Arabidopsis thaliana and Oryza sativa, was analyzed.
A number of copies contain large deletions however no obvious relationship between expression levels and sequence conservation could be identified.
In our study, no correlation could be established between the expression and the evolutionary conservation of these new miRNAs.
