Evolution of plant conserved microRNAs after whole-genome duplications.

MicroRNAs (miRNAs) are a specialized class of small silencing RNAs that regulate gene expression in numerous biological processes in eukaryotes. While the evolutionary dynamics of protein-encoding genes after plant whole-genome duplications (WGDs) has been extensively studied, the patterns of evolution for conserved MIRNAs (miRNA genes) post WGDs are less understood. In this study, we systematically investigated miRNAs and their targets in six plant species with varying WGD histories. Our findings reveal that WGDs significantly contribute to the expansion of conserved miRNA families. Notably, through homologous analyses of conserved miRNA families, we discovered that beyond the loci derived from WGDs and other duplication events, some conserved miRNA families have independently gained new loci and/or lost syntenic loci in specific lineage or species through evolution. Additionally, our analyses of sequence divergence in conserved miRNAs showed that the mature sequences of miRNA duplicates gradually diverge following WGDs, with this sequence divergence being correlated with that of their adjacent protein-coding genes after recent WGDs. Furthermore, expression and functional divergence analyses of duplicated targets in different miRNA-target interaction scenarios suggest that conserved miRNAs may play crucial roles in the expression of duplicated genes and related regulatory networks following WGDs. In summary, our analyses reveal universal evolutionary patterns of plant conserved miRNAs following WGDs, and provide evidence that some miRNA copies in conserved families originated independently during evolution.