This study is led by Professor Yanjie Xie (Laboratory Center of Life Sciences, College of Life Sciences, Nanjing Agricultural University, Nanjing, China). The authors investigated the molecular interplay between abscisic acid (ABA) signaling and reactive oxygen species (ROS) in regulating stomatal movement and drought responses. Although it is well established that ABA triggers ROS production via the NADPH oxidase RBOHD, how ABA transcriptionally regulates RBOHD and how ROS signals feed back into the ABA network remained elusive.
The researchers first demonstrated that ABI4 directly activates RBOHD transcription in response to ABA. In the abi4 mutant, ABA-induced RBOHD expression and ROS accumulation were significantly attenuated, and stomatal closure was impaired. Genetic analysis showed that abi4 rbohd double mutants exhibit more severe ABA-hyposensitive phenotypes than single mutants, indicating that ABI4 and RBOHD function in the same pathway.
Unexpectedly, the authors discovered that RBOHD-produced ROS mediate oxidative post-translational modification of ABI4. Using sulfenylation-specific antibodies, they found that ABA triggers rapid and reversible sulfenylation of ABI4 at Cys250. This modification enhances ABI4’s DNA-binding affinity to the RBOHD promoter and boosts its transcriptional activity, thereby promoting further ROS production in a positive feedback manner.
Site-directed mutagenesis confirmed that Cys250 is essential for this redox regulation. ABI4Cys250Ala failed to restore ABA-induced stomatal closure or drought tolerance in abi4 mutants, and could not activate downstream drought-responsive genes such as DREB1A , NCED3 , and RAB18 . Physiological assays showed that plants expressing the non-oxidizable ABI4 variant exhibit reduced ROS bursts, impaired stomatal closure, and decreased survival under drought stress.
By integrating molecular, genetic, and physiological approaches, this work establishes a self-amplifying regulatory loop: ABA → ABI4 → RBOHD → ROS → ABI4 sulfenylation → enhanced ABI4 activity → more ROS. This redox-controlled module ensures robust and tunable stomatal responses to environmental cues, and provides a mechanistic basis for the long-observed crosstalk between ABA and ROS.
In summary, this study not only uncovers a novel post-translational regulatory mechanism of ABI4, but also offers potential targets for improving crop drought tolerance through genetic engineering or molecular breeding.
See the article:
Oxidation of ABI4 by RBOHD-derived ROS integrates redox signaling into ABA and drought stress responses
https://www.sciencedirect.com/science/article/pii/S2662173826000512
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The oxidation of ABI4 by RBOHD-derived reactive oxygen species integrates redox signaling into abscisic-acid and drought-stress responses
21-Mar-2026