5.4 ROS signaling
ROS scavenging and signaling play a key role in plant responses to both
biotic and abiotic stress conditions (Pastori & Foyer, 2002; Fujita et
al., 2006; Ton et al., 2009; Atkinson & Urwin, 2012; Kissoudis et al.,
2014; Morales et al., 2016). During abiotic stress conditions, such as
osmotic stress and high light, elevated levels of ROS must be detoxified
by the plant to prevent damage to cell membranes and degradation of
proteins, including important protein complexes related to
photosynthesis (Staehelin & van der Staay, 1996; Wu et al., 2013; van
Eerden et al., 2015; Kobayashi, 2016). Detoxification occurs through the
action of antioxidants, including superoxide dismutase (SOD), enzymes
and metabolites from the ascorbate‑glutathione cycle, and catalase (CAT)
(see de Carvalho et al., 2013 for review). During biotic stress
conditions, plants generate ROS to limit pathogen spread by initiating
the hypersensitive response and cell death (Atkinson & Urwin, 2012). In
both cases, ROS serve as a signal of stress conditions and elicit
downstream ROS-responsive genes. This includes transcription factors,
ABA biosynthetic genes, and antioxidant metabolism genes (Atkinson &
Urwin, 2012). Additionally, many biotic and abiotic stresses activate
ROS production through NADPH oxidase (RBOH) proteins. RBOH proteins are
regulated through several post-translational mechanisms by both biotic
(aphid, bacterial, fungal infection) and abiotic stresses (salinity,
heat, high light), making them a central hub for integrating multiple
stress conditions (Rivero et al., 2022). Therefore, master regulators of
ROS signaling mechanisms would be key targets for future research.