Autophagy and apoplastic ascorbic acid (AsA) play important roles in plant drought tolerance. However, the trans-plasma membrane transport of AsA and its association with autophagy during drought stress are unclear. Here we report an AsA-induced autophagy pathway in plants, wherein plasma-membrane-located cytochrome b561 and DOMON domain (CYBDOM) proteins play positive roles. CYBDOM proteins from the resurrection plant Boea hygrometrica (BhDB) and Arabidopsis (AtDB1) can transport electrons across the plasma membrane using intracellular AsA as an electron donor and apoplastic monodehydroascorbic acid or Fe 3+ as electron acceptors in Xenopus laevis oocytes. Increased apoplastic AsA, autophagy and drought tolerance are observed in BhDB - and AtDB1 -overexpressing Arabidopsis compared with the wild type. CYBDOM proteins interact with respiratory burst oxidase homologue D (RbohD), which serves as the adaptor to bind autophagy related gene 8 protein (ATG8) and cargo protein for autophagic degradation. AsA increases AtDB1 protein level and its interaction with RbohD. Together, the AsA-activated CYBDOM–RbohD synergy to induce autophagy suggests a novel mechanism in plant drought and desiccation tolerance.
Ao Li,Shuo Wang,Xiushuo Liang,Sheng Luo,Honghong Hao,Renjing Wan,Shaowu Xue
Salinity induces the accumulation of reactive oxygen species (ROS) in plants, thereby regulating plant growth and development, including seed germination. However, the molecular mechanisms underlying the regulation of ROS homeostasis in response to salt stress remain largely unknown. Here, we showed that an leucine‐rich‐repeat receptor‐like kinase, REK1, regulates ROS production by phosphorylating the NADPH oxidase respiratory burst oxidase homolog D (RBOHD) in Arabidopsis in response to salt stress. Salt‐induced ROS accumulates extensively in rek1 mutants, causing stress that reduces the seed germination rate of rek1 below that of the wild‐type (Col‐0), resulting in the salt‐sensitive phenotype. Furthermore, REK1 interacts with RBOHD and phosphorylates it at Ser163, thereby regulating its NADPH oxidase activity and influencing ROS production under salt stress. Genetic data revealed that the salt‐sensitive phenotype of rek1 is rescued in rek1 rbohd mutants. In summary, our study revealed a salt stress regulation mechanism that modulates ROS production in Arabidopsis through the REK1‐RBOHD pathway. The study shows that REK1, a member of the leucine‐rich repeat receptor‐like kinase family, increases plant tolerance to salt stress during seed germination by phosphorylating NADPH oxidase respiratory burst oxidase homolog D, thereby regulating its oxidase activity and reactive oxygen species levels.
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