Essential genes are usually less likely to be lost during evolution, whereas dispensable genes are lost more frequently. The plant microRNAs (miRNAs) regulate diverse genes involving in plenty of biological functions including development and stress response. However, how miRNAs evolve during plant radiation are little understood when insufficient miRNA sequencing data from basal lineages.  

Integrating a basal eudicot, sacred lotus, and other plant miRNAdata, Prof. YANG Pingfang and SHI Tao from Wuhan Botanical Garden found different ancient miRNA families that arose before eudicot radiation showed different evolutionary trajectories.  

Those ancient miRNA families with higher copy and target numbers, and older age were more likely to be retained in plant descendants and more conserved in (hairpin-structured) miRNA gene sequences. More interestingly, a large portion of the well conserved miRNA families in plant lineages could target transcription factors (TFs). Researchers found miRNA families that targeted TFs were preferentially retained after sacred lotus genome duplication. Moreover, sequence divergence in MIRNAs (miRNA genes) accelerated expression divergence of their target genes in lotus. 

This study unravels several important factors and selection that determine the miRNA family distribution in plants and duplicated genomes, and provides evidence for functional impact of MIRNAs sequence evolution. 

 It was supported by The Knowledge Innovation Project of the Chinese Academy of Sciences and National Natural Science Foundation of China. Results were published in Plant Journal entitled “The evolution of plant microRNAs—insights from a basal eudicot sacred lotus”.