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Jamie A O`Rourke

Research Geneticist (Plants)


Corn Insect & Crop Genetics Research Unit


 /ARSUserFiles/43345/Unit Photos/O'Rourke J 225x300.jpg    

Jamie O’Rourke
Research Geneticist (Plants)
716 Farmhouse Lane
1567 Agronomy Hall
Iowa State University
Ames, Iowa 50011-4014
515-294-7824
515-294-9359 (Fax)

Education:

 

Research Interests:

Improving crop yields and mitigating losses to biotic and abiotic stress is critical to food security. While crop production must support continued population growth, it must also become more sustainable, with fewer inputs and reduced environmental impact. My primary research interests are identifying and understanding gene expression changes induced by abiotic stress. My work focuses on iron and phosphorus deficiency in legumes. Iron (Fe) is an essential micronutrient for plants, involved in multiple physiological processes including photosynthesis and electron transport. Though Fe is abundant in soil, environmental conditions including high pH, calcareous soil composition, and aerobic conditions often render Fe insoluble and unavailable for plants. Of the worlds cultivated soils, roughly 30% are calcareous, including the upper Midwestern United States where over 90% of US soybeans are produced. Fe deficiency in soybean results in end of season yield loss. Conversely, excessive Fe is toxic, resulting in plant death. Thus, iron uptake is tightly regulated. Similarly, although phosphate is plentiful in soils, slow diffusion and high fixation within soils makes phosphorus one of the most rate-limiting nutrients in agricultural production. Thus, phosphorus is commonly applied as a fertilizer, but plants only utilize about 20% of the applied fertilizer with the rest lost through run-off and contributing to environmental problems such as water eutrophication. 

My lab focuses on understanding how plants alter gene expression patterns in response to iron and phosphorus deficiency to survive low nutrient growth conditions. To understand how these genes are involved in abiotic stress responses we use sequencing of RNA (RNA-seq) to identify all expressed and differentially expressed gene sequences. We also use a suite of associated tools to visualize expression patterns to identify biological pathways associated with stress tolerance. To understand the effect of a specific gene on abiotic stress tolerance, we knock down its expression in soybean using virus induced gene silencing (VIGS). These approaches have found high overlap in the genes affected by iron and phosphorus deficiency, indicating these nutrient deficiencies alter similar pathways. Interestingly, multiple stress exposure can alter gene expression patterns from those observed after a single stress event, suggesting plants can prime stress responses.

These findings have important implications for plant breeding programs working on improved abiotic stress tolerance. Understanding the biological pathways associated with stress tolerance will facilitate the development of cultivars with enhanced stress tolerance and improved nutrient use efficiency.

Aims: Improve understanding of how plants alter gene expression patterns and associated biological networks in response to iron and phosphorus deficiency to survive low nutrient growth conditions.

Background: While crop production must support continued population growth, it must also become more sustainable, with fewer inputs and reduced environmental impact. My primary research interests are identifying and understanding gene expression changes induced by abiotic stress, specifically iron and phosphorus deficiency, in legumes. Iron (Fe) is an essential micronutrient, involved in multiple physiological processes.  Though abundant in soil, environmental conditions often render Fe insoluble and unavailable for plants. Of the worlds cultivated soils, roughly 30% are calcareous, including the upper Midwestern United States where over 90% of US soybeans are produced.  Fe deficiency in soybean results in end of season yield loss.  Conversely, excessive Fe is toxic, resulting in plant death.  Thus, iron uptake is tightly regulated.  Similarly, although phosphate is plentiful in soils, slow diffusion and high fixation within soils makes phosphorus (Pi) one of the most rate-limiting nutrients in agricultural production.  Thus, Pi is commonly applied as a fertilizer, but plants only utilize about 20% of the applied fertilizer with the rest lost through run-off and contributing to environmental problems such as water eutrophication.

Approach: We utilize a suite of functional genomic tools including RNA sequencing (RNA-seq), to identify all expressed and differentially expressed gene sequences.  Virus induced gene silencing (VIGS) and VIGS coupled with RNA-seq is used to characterize gene function and identify associated gene networks.  Using bioinformatic tools we are able to visualize expression patterns and associate specific biological pathways with stress tolerance.

Outcomes:  Our work has helped the hallmarks of the soybean iron deficiency stress response.  We have determined different nutrients affect the same biological pathways, though possibly in different ways and confirmed that early stress exposure may promote stress acclimation processes in soybean. Understanding the biological pathways associated with stress tolerance will facilitate the development of cultivars with enhanced stress tolerance and improved nutrient use efficiency.