Trilateral FPP 2023: FloResEng - Engineering Endogenous Oxygen Sensing for Improved Flood Resilience in Cereals

About This Grant

Consistent high yields of commodity crops in the U.S. fosters economic prosperity within the agriculture sector that benefits consumers. A significant challenge in crop production is maintenance of the narrow range of soil moisture and oxygen that maximize the capture of water and nutrients necessary for plant growth and fitness. The oversaturation of soils is caused by varied factors including uneven field contours, poor drainage, and periods of intense rain. In animals and plants, oxygen is essential for production of cellular energy. Soil saturation or compaction limits the level of oxygen available to root cells for their normal function. Previous studies have shown how plants cells respond to sudden or prolonged periods of insufficient oxygen (hypoxia). These responses cause changes in cell functions and plant growth that can lead to better oxygen retention or protect tissues until oxygen levels are restored. This project leverages the current understanding of hypoxia sensing, response mechanisms, naturally occurring variation and gene engineering of an oxygen sensor protein to alleviate negative impacts of hypoxia on nutrient uptake and growth. Experimentation will design and test slight changes in the key oxygen-sensing protein of critical commodity crops, which will be tested for their effect on hypoxia. This strategy is a promising path towards establishing more consistent crop yields. This project will enhance the scientific workforce by training a postdoc and undergraduate students in cutting-edge techniques. Plants sense and respond to low cellular oxygen (hypoxia), which ensue when soils are waterlogged, tissues undergo partial to submergence, and in some organs during development. Hypoxia responsive genes are controlled by Group VII ethylene response transcription factors (ERF-VIIs) that are constitutively synthesized but only stabilize when endogenous oxygen levels drop below a threshold. Plant Cysteine Oxidases (PCOs) are conserved cellular oxygen sensors that catalyze the conversion of ERF-VIIs to an N-degron destined for proteasome mediated degradation. Collaborators in the U.K. have identified a “tunnel” within Arabidopsis PCOs that controls the rate at which oxygen is delivered to the enzyme’s active site. Engineering this “tunnel” alters the oxygen binding threshold of PCOs, providing a route to modulate ERF-VII stabilization. Fine-tuning of ERF-VII levels influences the hypoxia response and flooding resilience. This project will leverage this knowledge and the conserved structure of PCOs to test the outcomes of PCO modification on ERF-VII stabilization in the cereals rice and barley. Specifically, this project will exploit pangenome variation and structure-function modeling to predict PCO modifications that tune oxygen binding and enzyme kinetics. Structure-guided modification of the PCO tunnel will then be tested in vitro, protoplasts, and in transgenic or edited plants. Outcomes include (i) genotypes of rice and barley with altered low oxygen sensitivity ready for field testing; (ii) dissemination of data and technology; and (iii) team-based authentic research experience module in engineering for crop improvement, valuable in industry and education. This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.