Degree Type


Date of Award


Degree Name

Master of Science



First Advisor

Randy C. Shoemaker


Soybean (Glycine max (L.) Merr.) is the second most abundant crop in the United States, with a total crop value of nearly $39 billion in 2010. U.S. soybean exports are used as an important protein and oil source in over 80 countries. Abiotic stress, such as iron deficiency chlorosis (IDC), threatens soybean yields, which affect farmers' profits in the United States as well as nutrition of consumers all over the world. IDC occurs when iron is unavailable to soybean roots, often in the calcareous soils of the upper Midwest United States. Iron stress causes a decrease in chlorophyll production, resulting in interveinal chlorosis (yellowing between veins), stunting, and yield losses of up to 80%, which cost U.S. farmers over $120 million in 2004. Improving yields benefits farmers as well as those in developing countries, who consume beans as a main source of proteins and nutrients, such as iron. Understanding the genetic basis behind iron efficiency in soybean will aid in breeding programs to decrease economic losses from IDC and improve global nutrition.

A recent microarray study found many DNA replication and repair genes to be differentially expressed during iron stress, but their role has not been studied. This work studies one such gene family, single-stranded DNA binding protein replication protein A (RPA), during iron stress. The first study found RPA genes had opposite expression patterns in two near-isogenic lines (NILs) of soybean, differing only in their iron efficiency, after 24 hours of iron stress. The second study finds silencing of RPA subunit 3 (RPA3) improved IDC symptoms in PI 547430 (Isoclark, iron-inefficient) during iron stress. The expression patterns of RPA genes during iron stress and improvement in IDC symptoms upon RPA3 silencing provide intriguing details to our understanding of the mechanisms of iron efficiency in soybean.


Copyright Owner

Sarah Atwood



Date Available


File Format


File Size

98 pages