The function of Osa-miR5075–MAIF1–OsMT2b in ROS homeostasis and drought stress responses in rice

The fine balance between reactive oxygen species (ROS) accumulation and scavenging is critical for plant cell survival under abiotic stress. Metallothioneins (MTs) are small, cysteine‑rich proteins involved in ROS scavenging, but their protein stability regulation remains unclear under abiotic stress. The F‑box protein MAIF1 is stress‑responsive in rice, yet its function as an SCF (SKP1–CUL1–F‑box) E3 ligase component and its role in ROS homeostasis have not been established. In this study, we demonstrated that MAIF1 assembles with OSK20 and OsCUL1g to form an SCF E3 ubiquitin ligase complex. We further identified the metallothionein OsMT2b as a substrate of the SCF^ MAIF1 complex and confirmed that MAIF1 promotes the ubiquitination and subsequent degradation of OsMT2b. OsMT2b exhibited cross‑species ROS‑scavenging activity in carnation and apple. Moreover, we revealed that MAIF1 is negatively regulated by Osa - miR5075 . Transgenic plants with STTM‑mediated suppression of Osa - miR5075 exhibited increased ROS accumulation and increased sensitivity to drought stress. Our study reveals the Osa - miR5075 –MAIF1–OsMT2b regulatory module that controls ROS homeostasis and drought stress. These findings provide an important theoretical basis and candidate genes for the genetic improvement of stress tolerance in crops.