OsMADS27 Transcription Factor in Rice: Structure, Functional Significance, and Emerging Role in Abiotic Stress Tolerance

This narrative review synthesizes current knowledge on MADS-Box 27 (OsMADS27), a member of the AGL17 clade in rice that has emerged as a regulatory node linking nitrate signaling, root development, and abiotic stress tolerance. Because most functional and mechanistic studies on OsMADS27 to date have been conducted in rice, this review is centered on Oryza sativa, with cross-species comparisons used for evolutionary and comparative context. Specifically, we summarize the gene and protein structure, phylogenetic position, expression profile, upstream and downstream regulation, and emerging functional significance of OsMADS27. OsMADS27 is a typical MIKC-type MADS-box protein with root-preferential expression, and its activity is strongly influenced by nitrate availability and miR444-mediated regulation. Evidence from functional genomics, transcriptomics, ChIP-based studies, and transgenic analyses suggests that OsMADS27 contributes to the regulation of root architecture, nitrate uptake, hormonal crosstalk, and stress-responsive pathways. Notably, OsMADS27 enhances salt tolerance through nitrate-dependent activation of downstream targets such as OsHKT1;1 and OsSPL7, contributing to ion homeostasis and salinity tolerance. Recent findings also suggest roles in grain size regulation and yield improvement, expanding its significance beyond root biology. This review compares OsMADS27 with AGL17-clade genes and highlights its value for crop improvement aimed at salinity tolerance and nitrogen use efficiency. However, important research gaps remain, particularly the limited field-level validation, the absence of integrated multi-omics analyses, and the lack of functional studies of OsMADS27 orthologs in non-rice crops. Overall, OsMADS27 represents promising rice-centered target for future biotechnology applications, while its translational relevance to other cereals remains to be established through orthology analysis and field-level evaluation.