Reactive oxygen and nitrogen species (RONS) signalling in seed dormancy release, perception of environmental cues, and heat stress response

Seed germination is a crucial plant-life process whose success depends largely on the seed's ability to germinate under favourable environmental conditions. Through molecular signalling, a seed is able to perceive environmental information, assimilate it, and transmit signals that determine its destiny. Reactive Oxygen and Nitrogen Species (RONS) function as signalling molecules that influence multiple phases of plant development. In the process of seed germination, their presence generally promotes germination completion, though not to the same extent in all species and environments. As signalling molecules, they participate in the sensing of light and temperature fluctuations as favourable germination cues, but they also play a role in inhibiting germination when temperatures exceed the optimal range, preventing seedling exposure to heat. Depending on environmental conditions, RONS set up crosstalk with the major phytohormones involved in germination, ABA, GA, and even auxin, regulating their biosynthesis and signalling. Here, we show relevant studies on how RONS exert seed germination control on multiple levels, such as through protein oxidation, epigenetic control, promotion of phytohormone key-metabolism genes expression, post-translational protein modifications, and redox interactions with DOG1. This review summarises the current understanding of the role of RONS in the seed, from its maturation to the transduction of environmental conditions. Special consideration is given to the RONS-mediated germination response to favourable stimuli, such as light or temperature fluctuations, and to conditions that inhibit germination, such as high temperatures.