Cai Huiren, Zhao Bingke, Liang Kexin, Yuan Peiguo, Zhang Caizhen, Yang Simiao, Duan Sujuan, Jin Hong-Lei, Wang Peng, Liu Bing, Liu Jun
State Key Laboratory of Biocontrol, Guangdong Provincial Key Laboratory of Plant Stress Biology, School of Life Sciences, Sun Yat-Sen University, Guangzhou, 510275, China.
Department of Plant Pathology and Microbiology, Texas A&M University, College Station, 77840-2132, TX, USA.
J Integr Plant Biol. 2025 May 12. doi: 10.1111/jipb.13929.
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.
叶绿体是捕获太阳能和建立植物免疫的关键细胞器。在光合作用和病原体防御过程中，叶绿体中会发生高度氧化还原活性反应，并产生大量活性氧（ROS）。然而，我们对不同光照条件下植物免疫中叶绿体产生的ROS生物合成的了解有限。在此，我们报道叶绿体定位蛋白高光敏1（HHL1）作为拟南芥中AvrRpt2触发免疫的双重调节因子，通过调节叶绿体产生的ROS水平，在不同光照强度下激活对病原体感染的适当反应。在正常光照条件下，HHL1通过促进AvrRpt2诱导的叶绿体产生的ROS积累、启动水杨酸信号传导以及诱导编码ROS清除酶的基因表达，正向调节AvrRpt2触发的免疫。相比之下，在高光（HL）条件下，HHL1具有相反的作用，在HL胁迫减弱AvrRpt2触发的免疫时，作为这些免疫反应的抑制因子发挥作用。这些发现表明，HHL1通过以光照强度依赖的方式调节ROS稳态来调节AvrRpt2触发的免疫。总的来说，我们的结果为叶绿体在植物免疫和光照强度相互作用中的作用提供了见解。
