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United States Department of Agriculture

Agricultural Research Service

Research Project: ABSORPTION AND METABOLISM OF ESSENTIAL MINERAL NUTRIENTS IN CHILDREN

Location: Children's Nutrition Research Center

Title: Variation and inheritance of iron reductase activity in the roots of common vean (Phaseolus vulgaris L.) and association with seed iron accumulation QTL

Authors
item Blair, Matthew -
item Knewtson, Sharon -
item Astudillo, Carolina -
item Li, Chee -
item Fernandez, Andrea -
item Grusak, Michael

Submitted to: Biomed Central (BMC) Plant Biology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: October 5, 2010
Publication Date: October 5, 2010
Citation: Blair, M.W., Knewtson, S.J., Astudillo, C., Li, C.M., Fernandez, A.C., Grusak, M.A. 2010. Variation and inheritance of iron reductase activity in the roots of common vean (Phaseolus vulgaris L.) and association with seed iron accumulation QTL. Biomed Central (BMC) Plant Biology. 10:215.

Interpretive Summary: Iron deficiency anemia is a global problem that often affects women and children of developing countries and is based on diets that are low in iron. Plants, such as, common bean take up iron through a process that involves an iron reduction mechanism in their roots; this reduction is required to convert ferric iron to ferrous iron, prior to the uptake of ferrous iron into the roots. Root absorbed iron is critical for the iron nutrition of the plant, and for the delivery of iron to the shoot and ultimately the seeds. Legume seeds, including those of common beans, are good sources of iron because they are generally rich in this element, but we would like to understand how to increase seed iron levels even more. The objectives of this study were to determine the genetic variability for root iron reductase activity in a range of bean types and in a special bean population that had low and high seed iron concentrations (DOR364 and G19833). We also wished to identify regions of the bean plant's genome (chromosome positions) that were associated with elevated root iron reductase activity. DOR364 and G19833, and nine other cultivated or four wild beans, were found to differ in root iron reductase activity. A single major genome region was found for root iron reductase activity in plants grown with iron-limited conditions on chromosome b02 and another major genome location was found with iron sufficient conditions on chromosome b11. Interestingly, genetic markers for bean iron reductase genes were found on chromosomes b06 and b07, and thus, did not align with either of the root iron reductase activity genome locations. These results are important because they point to the existence and location of other genes that are involved in controlling iron acquisition in bean.

Technical Abstract: Iron deficiency anemia is a global problem, which often affects women and children of developing countries and is based on diets that are low in iron. Strategy I plants, such as common bean (Phaseolus vulgaris L.) take up iron through a process that involves an iron reduction mechanism in their roots; this reduction is required to convert ferric iron to ferrous iron, prior to the uptake of this form. Root absorbed iron is critical for the iron nutrition of the plant, and for the delivery of iron to the shoot and ultimately the seeds. Legume seeds, including those of common beans, are good sources of iron because they are generally rich in this element. The objectives of this study were to determine the variability, and inheritance for iron reductase activity in a range of genotypes and in a low x high seed iron cross (DOR364 x G19833), to identify quantitative trait loci (QTL) for this trait, and to assess possible associations with seed iron levels. The experiments were carried out with hydroponically grown plants that provided different amounts of iron varying between 0 and 20 uM Fe (III)-EDDHA. The parents, DOR364 and G19833, and nine other cultivated or four wild beans, were found to differ in iron reductase activity. Based on these initial experiments, two growth conditions (iron limited and iron sufficient) were selected as treatments for evaluating the DOR364 x G19833 recombinant inbred lines. A single major QTL was found for iron reductase activity under iron-limited conditions (1 uM Fe) on linkage group b02 and another major QTL was found under iron sufficient conditions (15 uM Fe) on linkage group b11. Associations between the b11 QTL were found with several QTL for seed iron. Genes conditioning iron reductase activity in iron, sufficient bean plants appear to be associated with genes contributing to seed iron accumulation. Markers for bean iron reductase (FRO) homologues were found on linkage groups b06 and b07, with in silico mapping based on common bean synteny with soybean and Medicago confirming that the Pv07 locus is homologous with loci on Gm10 and Mt01. Neither locus aligned with the QTL for iron reductase activity, but the fact that the QTL for iron reductase activity under iron sufficiency conditions on bean chromosome b11 aligned with seed iron accumulation QTL make it an interesting locus for further analysis, especially as it may be homologous to other legume genes controlling iron homeostasis. The QTL for iron reductase activity under iron limited conditions may be useful in environments where beans or other legumes are grown under iron deficiency in alkaline soils, while the QTL for iron reductase under sufficiency conditions may be useful for selecting for enhanced seed nutritional quality.

Last Modified: 9/21/2014
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