ARS | Publication request: Microarray analysis of iron deficiency chlorosis in near-isogenic soybean lines

Submitted to: Biomed Central (BMC) Genomics
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: December 21, 2007
Publication Date: December 21, 2007
Citation: O'Rourke, J.A., Charlson, D.V., Gonzalez, D.O., Vodkin, L.O., Graham, M.A., Cianzio, S.R., Grusak, M.A., Shoemaker, R.C. 2007. Microarray analysis of iron deficiency chlorosis in near-isogenic soybean lines. Biomed Central (BMC) Genomics. 8:476.

Interpretive Summary: Iron is an essential mineral required for growth and development in plants and animals. In the north central U.S. iron is often unavailable to some soybeans due to a combination of environmental conditions and their hereditary background. These plants have reduced yield which costs growers many millions of dollars. In this paper the authors identified genes involved in the response of soybean to iron unavailability. They used computer programs to sort out genes uniquely affected by iron stress versus those affected by general stress. They also showed that the 'inefficient' soybeans failed to increase the activity of an enzyme that helped the efficient soybeans to acquire iron. These results are important to help understand how plants acquire iron and have important implications in the nutritional value and productivity of soybeans, and other legumes.

Technical Abstract: RNA isolated from the roots of two near isogenic lines, which differ in iron efficiency, PI548533 (Clark; iron efficient) and PI547430 (IsoClark; iron inefficient), were compared on a spotted microarray slide containing 9,728 cDNAs from root specific EST libraries. A comparison of RNA transcripts isolated from plants grown under iron limiting hydroponic conditions for two weeks revealed 43 genes as differentially expressed. A single linkage clustering analysis of these 43 genes showed 57% of them possessed high sequence similarity to known stress induced genes. A control experiment comparing plants grown under adequate iron hydroponic conditions showed no differences in gene expression between the two near isogenic lines. Expression levels of a subset of the differentially expressed genes were also compared by real time reverse transcriptase PCR (RTPCR). The RTPCR experiments confirmed differential expression between the iron efficient and iron inefficient plants for 9 of 10 randomly chosen genes examined. To gain further insight into the iron physiological status of the plants, the root iron reductase activity was measured in both iron efficient and inefficient genotypes for plants grown under iron sufficient and iron limited conditions. Results showed that reduced iron availability failed to increase reductase activity in the inefficient NIL.