OsFLZ5 Enhances Drought Tolerance and ABA Sensitivity in Rice via Transcriptional Activation by OsbZIP23

Abstract

Drought stress presents a major challenge to global agriculture. FCS-Like Zinc Finger (FLZ) genes are transcriptionally responsive to environmental stimuli, yet their precise biological functions remain insufficiently characterized. Here, we demonstrate that OsFLZ5, a drought- and abscisic acid (ABA)-induced gene, enhances drought tolerance and ABA sensitivity in rice (Oryza sativa L.), but does not exhibit obvious adverse effects on crucial agronomic traits including yield and plant height. Overexpression (OE) of OsFLZ5 significantly improved survival rate, seedling growth, and biomass under both polyethylene glycol6000 (PEG6000)-simulated and soil-based drought conditions, whereas knockout (KO) lines exhibited impaired performance. Consistently, OE lines showed heightened sensitivity to ABA, while KO mutants were less responsive. OsFLZ5 promotes soluble sugar accumulation and reduces malondialdehyde and hydrogen peroxide levels after drought exposure. RNA sequencing revealed that OsFLZ5 modulates a suite of drought-responsive genes. Notably, we identified the bZIP transcription factor OsbZIP23 as a direct upstream regulator of OsFLZ5; it binds to the OsFLZ5 promoter and activates its expression, thereby contributing to enhanced drought resilience and ABA sensitivity. These findings establish the OsbZIP23–OsFLZ5 regulatory module as a new mechanism in the rice drought and ABA response, providing targets for developing drought-tolerant crops.