Comparing early transcriptomic responses of 18 soybean (Glycine max) genotypes to iron stress

Authors: KOHLHASE, DANIEL - Iowa State University; McCabe, Chantal; SINGH, ASHEESH - Iowa State University; O`Rourke, Jamie; Graham, Michelle

Submitted to: International Journal of Molecular Sciences
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 10/25/2021
Publication Date: 10/28/2021
Citation: Kohlhase, D.R., Mccabe, C.E., Singh, A.K., O'Rourke, J.A., Graham, M.A. 2021. Comparing early transcriptomic responses of 18 soybean (Glycine max) genotypes to iron stress. International Journal of Molecular Sciences. 22(21). Article 11643. https://doi.org/10.3390/ijms222111643.
DOI: https://doi.org/10.3390/ijms222111643

Interpretive Summary: Iron deficiency chlorosis (IDC) is nutrient stress that negatively affects crop quality and yield. Much of our knowledge of iron stress mechanisms comes from model plant species, not typically grown as crops. Since crops have been adapted to multiple climates around the world, there are likely multiple mechanisms for responding to iron stress. In soybean, genetic, genomic and bioinformatic studies suggest important differences in iron stress responses between crop and model species. However, these studies have been limited to a small handful of soybean lines, tissues or timepoints. To improve iron stress tolerance in soybeans and other crops, we need to expand these studies to include the genetic diversity present in germplasm collections. Therefore, ARS scientists in Ames, IA, and Iowa State University collaborators used whole genome expression analysis of 18 diverse soybean genotypes to examine leaf and root responses to one hour of iron stress. We confirmed a rapid response to iron stress, with most lines responding within 60 minutes, much faster than the model plant Arabidopsis. Further, there was little overlap between genes identified within each line, suggesting the lines utilized different molecular pathways to cope with iron stress. These initial findings suggest untapped genetic potential within the soybean germplasm collection that could be used for continued development and improvement of iron stress tolerant soybean.

Technical Abstract: Iron deficiency chlorosis (IDC) is an abiotic stress that negatively affects soybean (Glycine max [L.] Merr.) production. Much of our knowledge of IDC stress responses comes from model plant species. Gene expression, quantitative trait loci (QTL) mapping, and genome-wide association studies (GWAS) performed in soybean suggest stress response differences exist between model and crop species. Our current understanding of the molecular response to IDC in soybeans is largely derived from gene expression studies using near isogenic lines differing in iron efficiency. To improve iron efficiency in soybeans and other crops, we need to expand gene expression studies to include the diversity present in germplasm collections. Therefore, we used RNA-sequencing to examine expression differences in the leaves and root tissue of 18 diverse soybean genotypes in response to iron deficiency. We found a rapid response to iron deficiency across genotypes, most responding within 60 minutes of stress. There was little evidence of overlap of specific differentially expressed genes and comparisons of gene ontology terms and transcription factor families suggest utilization of different pathways in stress response. These initial findings suggest untapped genetic potential within the soybean germplasm collection that could be used for continued improvement of iron-efficiency in soybean.