# OsOFP3 Negatively Regulates Heat Stress Tolerance by Modulating H2O2 Homeostasis and Stomatal Aperture in Rice

## TL;DR

This study shows that the OsOFP3 protein in rice reduces heat stress tolerance by affecting hydrogen peroxide balance and stomatal behavior.

## Contribution

OsOFP3 is identified as a novel negative regulator of heat stress tolerance in rice through its molecular interactions and physiological effects.

## Key findings

- OsOFP3 overexpression reduces heat tolerance and increases reactive oxygen species in rice.
- OsOFP3 mutants show enhanced heat stress resistance and improved stomatal closure.
- OsOFP3 interacts with OsHTAS, a positive regulator of heat tolerance, through its RING domain.

## Abstract

Rice (Oryza sativa) is a staple crop that is highly susceptible to heat stress (HS), which severely impairs growth and yield. In this study, we identified the rice Ovate Family Protein OsOFP3 as a novel negative regulator in response to heat. Our results demonstrate that the expression of OsOFP3 is suppressed at both the transcriptional and protein levels under HS. Overexpression of OsOFP3 significantly reduces the survival rate of rice seedlings under HS and exacerbates chlorophyll degradation, membrane damage, and the accumulation of reactive oxygen species (H2O2 and O2−). In contrast, OsOFP3 mutants exhibit enhanced heat tolerance. Moreover, OsOFP3-overexpressing plants display increased stomatal opening and decreased stomatal closure under HS. Molecular interaction analysis further reveals that OsOFP3 interacts with the C-terminal domain of OsHTAS, a known positive regulator of heat tolerance encoding an E3 ubiquitin ligase, and this interaction depends on the RING domain of OsHTAS. Taken together, our findings indicate that OsOFP3 negatively regulates rice heat tolerance by disrupting ROS homeostasis, inhibiting stomatal closure, and potentially antagonizing the OsHTAS-mediated signaling pathway. This research provides new insights into the molecular mechanisms underlying HS tolerance in rice.