The role of Ancestral MicroRNAs in grass inflorescence development

Plant inflorescences are complex, highly diverse structures whose morphology is determined in meristems that form during reproductive development. Inflorescence structure influences flower formation, and consequently grain number, and yield in crops. Correct inflorescence and flower development require tight control of gene expression via complex interplay between regulatory networks. MicroRNAs (miRNAs) have emerged as fundamental modulators of gene expression at the transcriptional and/or post-transcriptional level in plant inflorescence development. First discovered more than three decades ago, miRNAs have proved to be revolutionary in advancing our mechanistic understanding of gene expression. This review highlights current knowledge of downstream target genes and pathways of some highly conserved miRNAs that regulate the maintenance, identity, and activity of inflorescence and floral meristems in economically and agriculturally important grass species, including rice (Oryza sativa), maize (Zea mays), barley (Hordeum vulgare), and wheat (Triticum aestivum). Furthermore, we summarize emerging regulatory networks of miRNAs and their targets to suggest new avenues and strategies for application of miRNAs as a tool to enhance crop yield and performance.