Mechanism of plant-pathogen competition for leaf water under high humidity elucidated: gene expression of enzyme involved in stomata opening to discharge water is targeted

January 16, 2026

Expected to contribute to pathogen control in the era of climate change

Researchers from Nara Institute of Science and Technology, in collaboration with those from the RIKEN CSRS, Tokyo University of Agriculture, and Saitama University, partly elucidated the mechanism of plant-pathogen competition in the highly humid environment, where plant disease problems are escalating. Bacterial pathogens that infect plant leaves grow in spaces between cells in leaves. They attract water into their surroundings to induce "water-soaking" in leaves under high humidity, thereby creating a favorable environment for their growth. The pathogens use so-called “effector” proteins to enhance water-soaking, thereby facilitating their infection. This process could be a double-edged sword for the bacteria because once the host plants recognize the proteins, its immune response could be induced. Plants have mechanisms to prevent water-soaking, which the bacterial pathogens need to overcome. However, such mechanisms remain poorly understood.

In this study, the researchers focused on a gene cluster whose expression level increases under high humidity in the model plant Arabidopsis thaliana. They found that the enzyme CYP707A3, which catabolizes abscisic acid, a compound that helps regulate water in plants, is induced as humidity increases. This process inhibits abscisic acid activity, leading to stomata opening to limit water-soaking. In addition, the researchers showed that, before this response starts, the calcium level in the cells rises as humidity increases, and transcription factor CAMTA3 drives CYP707A3 gene expression. They also found that the bacterial pathogen inhibits CYP707A3 expression, which is pivotal to the plant’s resistance, and identified the effector molecule for this inhibition. The findings of this study show how plants detect a humidity increase and activate immunity, and are expected to lead to the development of new technologies for pathogen control.

 

Original article

Nature Communications　doi: 10.1038/s41467-025-67469-y

S. Yasuda, A. Shinozawa, Y. Weng, A. Rajendram, T. Hirase, H. Ishizaki, R. Suzuki, S. Ueda, R. Sk, Y. Takebayashi, I. Yotsui, M. Toyota, M. Okamoto, Y. Saijo,

"Humidity-driven ABA depletion determines plant-pathogen competition for leaf water".

Contact

Masanori Okamoto
Team Director
Plant Chemical Genetics Research Team