Oxidative signalling in seed germination and early seedling growth: an emerging role for ROS trafficking and inter-organelle communication

Underground early development of higher plants includes two distinct developmental processes, seed germination and then skotomorphogenesis, a mechanism which favours elongation of the hypocotyl and helps the seedling to find light. Interestingly, both processes, which are regulated by plant hormones, have been shown to depend on reactive oxygen species metabolism and to be related to mitochondrial retrograde signalling. Here we review the recent outcomes in this field of research and highlight the emerging role of ROS communication between organelles and cell compartments. We point out the role of mitochondria as an environmental and developmental sensor organelle that regulates ROS homeostasis and downstream events and we propose future directions of research that should help better understanding the roles of ROS in germination and seedling emergence. ROS homeostasis regulates early steps of plant life Germination is a key phenological step in higher plants life since it allows the transition from a dry mature and quiescent seed to a growing and metabolically active seedling after protrusion of the embryonic axis through the seed surrounding structures [1]. The developing seedling will ultimately give rise to a young plant after autotrophy acquisition, but it will first follow a specific morphogenic plan called skotomorphogenesis in which hypocotyl elongation is promoted, chlorophyll synthesis inhibited and an apical hook develops to protect the meristem during emergence from the soil [2,3]. In agriculture, emergence is the visible outcome of completion of both germination and early seedling development steps that both differ in their adaptation ability to environmental issues. Knowing at which stage seedlings fail to establish under penalizing conditions (e.g. water stress, temperature

Automated summary

The early development of higher plants underground consists of two distinct processes: seed germination and skotomorphogenesis, both regulated by plant hormones and dependent on reactive oxygen species metabolism. Mitochondria play a key role in regulating ROS homeostasis and influencing cell development during these processes.