The Arabidopsis chloroplast protein HHL1 regulates AvrRpt2-triggered immunity via light-dependent reactive oxygen species homeostasis

doi:10.1111/jipb.13929

J Integr Plant Biol. ›› 2025, Vol. 67 ›› Issue (8): 2151-2166.DOI: 10.1111/jipb.13929 cstr: 32098.14.jipb.13929

• Research Article • Previous Articles Next Articles

The Arabidopsis chloroplast protein HHL1 regulates AvrRpt2-triggered immunity via light-dependent reactive oxygen species homeostasis

Huiren Cai¹, Bingke Zhao¹, Kexin Liang¹, Peiguo Yuan², Caizhen Zhang¹, Simiao Yang¹, Sujuan Duan³, Hong‐Lei Jin³, Peng Wang⁴, Bing Liu^1* and Jun Liu^1*

1. State Key Laboratory of Biocontrol, Guangdong Provincial Key Laboratory of Plant Stress Biology, School of Life Sciences, Sun Yat‐Sen University, Guangzhou 510275, China
2. Department of Plant Pathology and Microbiology, Texas A&M University, College Station, TX 77840‐2132, USA
3. Institute of Medical Plant Physiology and Ecology, School of Pharmaceutical Sciences, Guangzhou University of Chinese Medicine, Guangzhou 510275, China
4. School of Biological Sciences, The University of Hong Kong, Hong Kong 999077, China

^*Correspondences: Bing Liu (liubing@mail.sysu.edu.cn); Jun Liu (liujun93@mail.sysu.edu.cn, Dr. Liu is fully responsible for the distribution of all materials associated with this article)

Received:2024-10-28 Accepted:2025-04-13 Online:2025-05-12 Published:2025-08-01
Supported by:
This study was supported by the National Natural Science Foundation of China (NSFC) (32270300) to B.L.; NSFC (32470289) to J.L., and Fundamental Research Funds for the Central Universities, Sun Yat‐sen University (24hytd011) to J.L.

Abstract

Abstract: Chloroplasts are key organelles for capturing solar energy and establishing plant immunity. During photosynthesis and pathogen defense, highly redox-active reactions take place in chloroplasts and generate large amounts of reactive oxygen species (ROS). However, our knowledge of chloroplast-produced ROS biosynthesis in plant immunity under varying light conditions is limited. Here, we report that the chloroplast-localized protein HYPERSENSITIVE TO HIGH LIGHT 1 (HHL1) functions as a dual regulator of AvrRpt2-triggered immunity in Arabidopsis (Arabidopsis thaliana), by modulating levels of chloroplast-produced ROS to activate appropriate responses to pathogen infection under various light intensities. Under normal light conditions, HHL1 positively regulates AvrRpt2-triggered immunity by promoting AvrRpt2-induced chloroplast-produced ROS accumulation, initiating salicylic acid signaling, and inducing the expression of genes encoding ROS-scavenging enzymes. By contrast, under high light (HL) conditions, HHL1 has an opposite role, functioning as a repressor of these immune responses while HL stress attenuates AvrRpt2-triggered immunity. These findings reveal that HHL1 modulates AvrRpt2-triggered immunity by regulating ROS homeostasis in a light intensity-dependent manner. Collectively, our results offer insight into the role of chloroplasts in the crosstalk between plant immunity and light intensity.

Key words: Arabidopsis, HHL1, high light, plant immunity, ROS, salicylic acid

Huiren Cai, Bingke Zhao, Kexin Liang, Peiguo Yuan, Caizhen Zhang, Simiao Yang, Sujuan Duan, Hong-Lei Jin, Peng Wang, Bing Liu, Jun Liu. The Arabidopsis chloroplast protein HHL1 regulates AvrRpt2-triggered immunity via light-dependent reactive oxygen species homeostasis[J]. J Integr Plant Biol., 2025, 67(8): 2151-2166.

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The Arabidopsis chloroplast protein HHL1 regulates AvrRpt2-triggered immunity via light-dependent reactive oxygen species homeostasis

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