MicroRNA-Mediated Regulatory Mechanisms in Rice: Implications for Tissue Culture and Trait Improvement

Abstract

MicroRNAs (miRNAs), which are diminutive, endogenously produced, non-coding RNA entities, function as critical regulators of gene expression by engaging in post-transcriptional control pathways. In rice (Oryza sativa), miRNAs have become crucial molecular components in numerous physiological and developmental processes, particularly evident during the various stages of in vitro tissue culture, including callus induction, organogenesis, and somatic embryogenesis. These stages involve profound cellular reprogramming, where miRNAs coordinate the specific signalling compounds and transcriptional expression, including SPL, ARF, GRF, NAC, and MADS-box gene families. Functional studies have revealed that miRNAs, such as miR156, miR160, miR172, miR396, and miR408, influence critical traits including tiller formation, floral organ development, spikelet initiation, and grain filling. Moreover, miRNA gene expression undergoes dynamic changes in relation to tissue culture–induced stress, thereby influencing regeneration efficiency and morphogenic responses. Advances in sequencing technologies, degradome analysis, and target validation methods have enabled the discovery of novel rice-specific miRNAs with potential utility in enhancing transformation efficiency and reducing genotype dependency. The manipulation of miRNA pathways through overexpression or target mimicry holds significant promise for improving rice regeneration protocols and accelerating crop improvement strategies. Overall, miRNAs represent powerful tools for precise gene regulation and biotechnological interventions in rice.