Abstract: The selective degradation of aberrant mRNAs plays a vital role in ensuring cellular survival under stress conditions. Here, we investigated the role of OsFKBP20-1b, a splicing factor, in dehydration stress response in rice (Oryza sativa). We show that OsFKBP20-1b associates with the core nonsense-mediated mRNA decay (NMD) components, UP-FRAMESHIFT1 (OsUPF1) and OsUPF2, enhances their stability, thereby supporting the efficient degradation of aberrant transcripts during dehydration stress. These associations were demonstrated using bimolecular fluorescence complementation (BiFC), co-immunoprecipitation (Co-IP), and in vitro binding assays. Integrative analyses combining ribosome profiling and transcriptome sequencing further revealed that OsFKBP20-1b influences both alternative splicing (AS) patterns and translational dynamics of stress-responsive transcripts. Notably, loss of OsFKBP20-1b compromises OsUPF1- and OsUPF2-mediated decay of aberrant mRNAs under dehydration conditions. Consistent with these molecular defects, osfkbp20-1b mutant plants exhibited heightened sensitivity to dehydration stress. Together, our findings identify OsFKBP20-1b as a key regulator linking pre-mRNA splicing with cytoplasmic RNA surveillance during dehydration stress, thereby providing mechanistic insight into post-transcriptional control of stress adaptation in rice. These results advance our understanding of RNA quality control pathways in plants and suggest potential molecular targets for improving drought-resilience in crops.

Key words: alternative splicing (AS), drought stress, nonsense‐mediated decay (NMD), OsFKBP20‐1b, RNA surveillance