Abstract
Reactive oxygen species (ROS) are part of aerobic environments, and variations in the availability of oxygen (O2) in the environment can lead to altered ROS levels. In plants, the O2 sensing machinery guides the molecular response to low O2, regulating a subset of genes involved in metabolic adaptations to hypoxia, including proteins involved in ROS homeostasis and acclimation. In addition, nitric oxide (NO) participates in signaling events that modulate the low O2 stress response. In this review, we summarize recent findings that highlight the roles of ROS and NO under environmentally or developmentally defined low O2 conditions. We conclude that ROS and NO are emerging regulators during low O2 signalling and key molecules in plant adaptation to flooding conditions.
Highlights
A low oxygen (O2 ) availability characterized the atmosphere of Earth for most of its history [1]
Land plants evolved from algae around 500 million years ago [2], and the O2 content available today in the atmosphere is currently attributed to this event [3]
It is interesting that oxidative stress was applied to five-day-old Arabidopsis plants, in the juvenile phase when genes related to Reactive oxygen species (ROS) scavenging and signalling are positively regulated by ERF-VII [55]
Summary
A low oxygen (O2 ) availability characterized the atmosphere of Earth for most of its history [1]. In Arabidopsis, early ethylene entrapment due to submergence increases transcription of the NO-scavenger non-symbiotic phytoglobin 1 (PGB1), reducing the amount of NO availability and promoting ERF-VII stability [45] This event occurs prior to severe hypoxia and, acting as a priming event, enhances plant tolerance to the forthcoming stress. Arabidopsis rbohD mutants are very intolerant to anoxia [46] and negatively affected in ADH1 expression compared to wild type seedlings under waterlogging and hypoxia [41,54] This suggests that, under these conditions, ROS produced by RBOHD may represent a positive signal required for plant tolerance to hypoxia. It is interesting that oxidative stress was applied to five-day-old Arabidopsis plants, in the juvenile phase when genes related to ROS scavenging and signalling are positively regulated by ERF-VII [55]. The activation of a hypoxic response may enhance the survival of the leaf tissue to hypoxia arising from pathogen infection or may be aimed at activating a still unknown plant defence pathway, requiring the activity of an O2 -labile protein
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