2015
Identifying genetic pathways involved in iron efficiency in soybean
Contributor/Checkoff:
Category:
Sustainable Production
Keywords:
Abiotic stressAgricultureLand Use Water supply
Lead Principal Investigator:
Michelle Graham, USDA/ARS-Iowa State University
Co-Principal Investigators:
Adrienne Moran Lauter, Iowa State University
Project Code:
Contributing Organization (Checkoff):
Institution Funded:
Brief Project Summary:

The goals of this research are to characterize the iron stress response in soybean and identify genes and markers that can be used to improve tolerance to iron deficiency chlorosis and other nutrient deficiencies. It defines a signaling network for iron deficiency chlorosis in soybean identifying and characterizing key transcription factors, transporters and signaling elements. To achieve these results, work intends to identify candidate genes that regulate shoot to root signaling response to iron deficiency, use Virus Induced Gene Silencing (VIGS) to study the candidate iron deficiency signaling genes and determine if the genes associated with IDC tolerance also respond to other nutrient stressors affecting soybeans.

Key Benefactors:
farmers, agronomists, Extension agents, geneticists, soybean breeders, seed companies

Information And Results
Project Deliverables

1. Provide a definition of a signaling network for iron deficiency chlorosis in soybean.
2. Provide information on specific genes in other nutrient and abiotic stress pathways.
3. Provide results in a publicly available database of VIGS constructs.
4. Markers developed by the project will be incorporated into the SoyBase database.

Final Project Results

Using computational methods, we have analyzed gene activity (RNA-seq) in the iron efficient soybean line Clark, 1 and 6 hours after iron stress. We have identified 974 genes that respond to iron stress in either leaves or roots. In a separate experiment, we performed RNA-seq on Clark leaves and roots 30, 60 and 120 minutes after iron stress. As this experiment was done after a new version of the genome was out, we were able to identify more genes responding to iron stress; 7957 in the leaves and 7320 in the roots across the time points. In the leaves, we are interested in transcription factors and signaling proteins that signal to the root that more iron is needed for continued growth and development. In the root, we are interested in the genes that receive the shoot signal and initiate the uptake of additional iron from the soil and genes that transport iron from the root to shoot.

We have also taken advantage of data published by our group over the last ten years identifying hundreds of genes involved in IDC responses in IDC tolerant and susceptible lines. While the studies focused on late responses to IDC, they can still be used to identify genes that could improve or worsen IDC symptoms. By cross-referencing these experiments with the Soybean Virus Induced Gene Silencing (VIGS) website (http://soybase.org/SoyVIGS) we identified 130 VIGS constructs that were already available. So far, we have screened VIGS constructs for 52 different genes and 31 have yielded a visible phenotype ranging from alterations in growth, to reduced chlorophyll content and IDC-like symptoms. We have also tested 14 of the VIGS constructs on plants grown in well watered and drought conditions to see if any of the genes are associated with drought tolerance. Five of the constructs altered the severity of drought symptoms relative to controls. In addition, our laboratory is now making our own VIGS silencing constructs designed specifically from the early stress data.

We have made significant progress over the project. A manuscript detailing the 1 and 6 hour gene expression data has been published. Both PIs have been invited to speak about the research at National and International Meetings. We are collaborating with other groups at Iowa State to determine if genes identified in this proposal protect against other plant stresses including pathogens. In addition, we are contributing to the training of undergraduate and graduate students by involving them in the analysis of expression data and VIGS screens.

The United Soybean Research Retention policy will display final reports with the project once completed but working files will be purged after three years. And financial information after seven years. All pertinent information is in the final report or if you want more information, please contact the project lead at your state soybean organization or principal investigator listed on the project.