Unveiling what makes the reactive oxygen species burst in plant immunity transient

As plants respond to pathogens, an early burst of reactive oxygen species (ROS) is triggered, shaping immune defenses. These massive ROS production is transient and limited, to mitigate oxidative damage that this species can inflict on the plant itself. The intricate orchestration of ROS production involves activators like several kinases that phosphorylate the NADPH oxidase accounting for this ROS burst. But understanding the mechanisms that deactivate this process remains a challenge. A recent Commentary published in the New Phytologist journal comments on the discovery of a negative regulator of this oxidase that may contribute to fine-tuning ROS production in immunity, limiting the amount of H2O2 produced and aiding in making ROS production transient.

Miguel Angel Torres comments a recent publication in New Phytologist, that focuses on the crucial role of PB1 DOMAIN-CONTAINING PROTEIN (PB1CP) as a novel negative regulator of ROS production, shedding light on its involvement in the fine-tuning of ROS dynamics in response to pathogens (Goto et al., 2023; doi.org/10.1111/nph.19302). The transient burst of ROS, initiated by NADPH oxidases after pathogen recognition, is a key signaling component that mediates the establishment of plant defenses. In the model plant Arabidopsis thaliana, RESPIRATORY BURST OXIDASE HOMOLOG D (RBOHD) is the NADPH oxidase that accounts for most H2O2 detected after pathogen attack. Extensive research has elucidated various activation mechanisms of RBOHD (Figure 1). Several post-translational mechanisms, including binding of calcium, lipid signals and GTPase but especially phosphorylation by different kinases, govern the activation of this oxidase. However, limited understanding exists regarding the processes that deactivate this enzyme, thereby ensuring the transient nature of ROS production.

Goto et al. present a groundbreaking exploration into the regulatory mechanisms governing ROS production during plant immune responses. PB1CP, containing a PB1 domain akin to regulators of the mammalian phagocytic NADPH oxidase, emerges as a new RBOHD interactor that negatively regulates the active oxidase. PB1CP may exert this regulation by competing with kinases that activate RBOHD or by promoting endocytosis, leading to the degradation of the oxidase (Figure 1). Thus, his dynamic interplay may contribute to fine-tuning ROS production in immunity, limiting the amount of H2O2 produced and aiding in making ROS production transient.

Imagen: Figure 1. Mechanisms underlying the transient activation of oxidase RESPIRATORY BURST OXIDASE HOMOLOG D (RBOHD)-dependent reactive oxygen species production during plant immunity (from Torres, M. Á. (2024); http://dx.doi.org/10.1111/nph.1950 ).

Original Paper: Torres, M.-Á. 2024. Unveiling what makes the reactive oxygen species burst transient: the role of PB1CP in plant immunity. New Phytologist. DOI: 10.1111/nph.19502