Plant miRNAs: Biogenesis, Mode of Action, and Their Role

Abstract

MicroRNA (miRNAs) are a highly conserved, small, non-coding, single-stranded, endogenous class of RNA molecules, which are ~ 21–23 bp long nucleotide sequences mainly present in animals, plants, and some viruses. In the case of plants, miRNAs are well recognized as essential genetic tools for improving crop productivity by regulating various gene expression processes including modification, translational inhibition, or translational repression. The miRNA genes are transcribed by DNA-dependent RNA polymerase II, and the resulting transcript is modified during transcription to form the main transcript. The multiple protein complexes DCL1 (DICER LIKE1), C2H2 Zink finger protein, SERRATE (SE), double-stranded RNA binding protein, and G-patch structural protein (TGH) recognize and cleave these pri-miRNAs, which have partially complementary paired hairpin structures, to produce the precursor of miRNA. The HEN1 protein (methyltransferase), which is essential for the modification and stabilization of double-stranded miRNA, also methylates the miRNA. The advancement of knowledge related to biogenesis of miRNAs and their mode of action has disclosed their involvement in various regulatory processes. There are two well-known vital modes of action of miRNA at the post-transcriptional level, one is transcript degradation and another is translational repression. The 5’ UTR, coding regions, and gene promoters of their target genes have all been observed to interact with miRNA. There are many unanswered problems regarding miRNA synthesis and its method of action, particularly in relation to transcriptional control and other facets of RNA metabolism including splicing. The present book chapter summarizes the current knowledge about miRNA biogenesis and related molecular advancement along with their mode of action in plant morphogenesis processes. © 2025 selection and editorial matter, Peerzada Yasir Yousuf, Peerzada Arshid Shabir, and Khalid Rehman Hakeem; individual chapters, the contributors.