Periodic Reporting for period 1 - LOKI (Low oxygen, key ingredient of the plant stem cell niche?)
Reporting period: 2023-03-01 to 2025-08-31
Serving as final electron acceptor in respiration, the availability of oxygen in our planet’s atmosphere provided the efficient energy metabolism to drive evolution of complex multicellular organisms, including plants. Plants are remarkable in that they can produce their own oxygen via the hydrolysis of water during photosynthesis, but they also lack an active oxygen transport mechanism like those evolved in metazoans.
Therefore, environmental conditions where oxygen is limited (hypoxia) such as during flooding stress, pose a severe threat to plant survival and can lead to death when prolonged. However, it has been shown that several plant tissues exist in a state of chronic hypoxia, including maize anthers, lateral root primordia, germination and shoot apical meristems. This suggests that local hypoxia may play a positive role in regulating developmental processes, despite causing energy crisis in other plant tissue.
This ERC project challenges the paradigm of hypoxia as a solely stressful condition and investigates how local hypoxia might regulate meristem development and the growth of differentiating organs. This will be addressed through 1) the development of genetically encoded oxygen biosensors, which will unlock the ability to visualize and understand the role of oxygen gradients in plant tissue. 2) Genetic manipulation of the oxygen sensing machinery to test if and how oxygen gradients may affect plant development. The novel insights on how oxygen levels regulate development and the tools developed in this project may also lead to new innovations in order to improve growth and flooding stress resilience.
Therefore, environmental conditions where oxygen is limited (hypoxia) such as during flooding stress, pose a severe threat to plant survival and can lead to death when prolonged. However, it has been shown that several plant tissues exist in a state of chronic hypoxia, including maize anthers, lateral root primordia, germination and shoot apical meristems. This suggests that local hypoxia may play a positive role in regulating developmental processes, despite causing energy crisis in other plant tissue.
This ERC project challenges the paradigm of hypoxia as a solely stressful condition and investigates how local hypoxia might regulate meristem development and the growth of differentiating organs. This will be addressed through 1) the development of genetically encoded oxygen biosensors, which will unlock the ability to visualize and understand the role of oxygen gradients in plant tissue. 2) Genetic manipulation of the oxygen sensing machinery to test if and how oxygen gradients may affect plant development. The novel insights on how oxygen levels regulate development and the tools developed in this project may also lead to new innovations in order to improve growth and flooding stress resilience.
In order to visualize local hypoxia in plant tissue, we engineered and tested various genetically encoded oxygen biosensors. To this end, we characterized the oxygen response of oxygen-sensitive fluorescent proteins and improved existing hypoxia-signalling reporters. The main challenge here was in obtaining stable Arabidopsis plants expressing sensors with broad and high expression across various tissues. We now have a novel set of fluorescent tools able to report on a broad range of oxygen levels with high spatial resolution, and we are currently employing these to generate oxygen maps of specific organs and whole seedlings.
We made efforts to generate new tools to allow the manipulation of oxygen sensing in a time and spatial-controlled manner. Plants sense oxygen through the proteolysis of methionine-cysteine (MC)-initiating transcription factors and this regulation is initiated by a group of enzymes called PCOs. These are thiol-dioxygenases that use molecular oxygen to oxidize the N-terminal Cys residue of the aforementioned transcription factors. Hence, by manipulating the expression of PCO enzymes we aim to tune the ability of plants to sense hypoxia. Next, we will employ these new tools to unravel the molecular mechanism linking oxygen sensing to plant development.
We made efforts to generate new tools to allow the manipulation of oxygen sensing in a time and spatial-controlled manner. Plants sense oxygen through the proteolysis of methionine-cysteine (MC)-initiating transcription factors and this regulation is initiated by a group of enzymes called PCOs. These are thiol-dioxygenases that use molecular oxygen to oxidize the N-terminal Cys residue of the aforementioned transcription factors. Hence, by manipulating the expression of PCO enzymes we aim to tune the ability of plants to sense hypoxia. Next, we will employ these new tools to unravel the molecular mechanism linking oxygen sensing to plant development.
Our current progress has led us to be able to better visualize oxygen distribution in plant tissues. This is critical to understand the role that hypoxia plays in plant development, but the genetically encoded biosensors also hold potential to be used outside of the direct scope of this project. Indeed, biosensors that do not rely on plant-species specific components permit their use in other model plants and crops. They also provide a tool to image oxygen levels in whole plants during submergence, and to inform about the efficacy of morphological or metabolic adaptations to improve internal aeration during flooding stress.
By exploring the role that oxygen plays in plant development, we are able to better understand the molecular mechanisms underlying meristem maintenance and organogenesis by internal cues. This may also help to inform strategies for modifying plant growth and development by manipulating their atmospheric environment.
Our expectation for the remainder of the project is to comprehensively unravel the role that oxygen distribution plays in regulating the development and maintenance of various hypoxic niches. Through an understanding of the fundamental physiological and developmental role of hypoxia in meristems , we also intend to explore novel strategies to improve meristem or whole plant survival under hypoxic stress.
By exploring the role that oxygen plays in plant development, we are able to better understand the molecular mechanisms underlying meristem maintenance and organogenesis by internal cues. This may also help to inform strategies for modifying plant growth and development by manipulating their atmospheric environment.
Our expectation for the remainder of the project is to comprehensively unravel the role that oxygen distribution plays in regulating the development and maintenance of various hypoxic niches. Through an understanding of the fundamental physiological and developmental role of hypoxia in meristems , we also intend to explore novel strategies to improve meristem or whole plant survival under hypoxic stress.