RNA-Seq of grafted near-isogenic soybean (Glycine max) lines reveals root genotype drives shoot responses to iron deficiency chlorosis

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

Submitted to: Plant Stress
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 12/16/2024
Publication Date: N/A
Citation: N/A

Interpretive Summary: Iron deficiency chlorosis (IDC) negatively affects crop quality and yield. Previous studies from model species demonstrate the importance of the shoot in regulating iron uptake responses in the root. In this study, we used grafting of two nearly identical soybean lines with different levels of IDC tolerance (Clark and IsoClark) to demonstrate that the root drives tolerance to IDC in the soybean line Clark. Using whole genome expression analyses, we confirm that Clark shoots can influence IsoClark roots, but can only activate a general stress response. In contrast, we demonstrate that iron stress tolerant Clark roots can activate a robust iron stress response in shoots of the iron stress susceptible line IsoClark. This suggests a mobile signal, initiated in the roots, regulates iron stress responses in the leaves. Better understanding of the complex differences between crop and model species will aid in the development of crops with improved IDC tolerance.

Technical Abstract: Iron deficiency chlorosis (IDC) negatively affects crop quality and yield. Previous studies of model species demonstrate iron uptake in the roots is controlled or significantly influenced by the shoot. In this study, grafting of near-isogenic soybean lines Clark and IsoClark (contrasting iron stress phenotypes), demonstrated Clark rootstock drives phenotypic responses in IsoClark leaves two weeks after iron stress. RNA-seq analyses of leaves and roots from homo- and hetero-grafted plants 30 and 120 minutes after iron stress identified 518 and 846 differentially expressed genes (DEGs) in leaves and roots, respectively. Comparing DEG expression patterns between leaves from hetero- and homo-grafted plants at 30 minutes revealed the DEG expression pattern was determined by the genotype of the leaves. By 120 minutes the DEG expression pattern in the leaves, was determined by the genotype of the root. Grafts with a Clark rootstock induced genes involved in iron uptake and utilization at 30 minutes in the root and by 120 minutes in the leaves, regardless of the leaf genotype. This suggests a mobile signal, initiated in the roots, regulates iron stress responses in the leaves. Better understanding of the complex differences between crop and model species will aid in the development of crops with improved IDC tolerance.