Molecular and phenotypic characterization of transgenic soybean expressing the Arabidopsis ferric chelate reductase gene, FRO2

• Published in: Planta 2006-10, Vol.224 (5), p.1116-1128
• Main Authors: Vasconcelos, M, Eckert, H, Arahana, V, Graef, G, Grusak, M.A, Clemente, T
• Format: Article
• Language: English
• Subjects: Arabidopsis - genetics; Arabidopsis thaliana; Biological and medical sciences; Calcareous soils; Chlorophylls; enzyme activity; Ethylenediamines; ferric chelate reductase; FMN Reductase - genetics; FMN Reductase - metabolism; Fundamental and applied biological sciences. Psychology; gene expression regulation; Genes. Genome; genetic transformation; Glycine max; Glycine max - genetics; Glycine max - metabolism; Hydroponics; Hypochromic anemia; Introns; Iron; Iron - metabolism; Leaves; messenger RNA; Molecular and cellular biology; Molecular genetics; NADH or NADPH oxidoreductases; Nutrient deficiency; Plant Leaves - metabolism; plant proteins; Plant roots; Plant Roots - metabolism; Plants; Plants, Genetically Modified - genetics; Plants, Genetically Modified - metabolism; Protoplasts; reduction; root systems; Roots; Soil environment; soil nutrients; Soybeans; Transcription, Genetic; Transformation, Genetic; transgenes; Transgenic plants
• ISSN: 0032-0935; 1432-2048
• DOI: 10.1007/s00425-006-0293-1

Soybean (Glycine max Merr.) production is reduced under iron-limiting calcareous soils throughout the upper Midwest regions of the US. Like other dicotyledonous plants, soybean responds to iron-limiting environments by induction of an active proton pump, a ferric iron reductase and an iron transporter. Here we demonstrate that heterologous expression of the Arabidopsis thaliana ferric chelate reductase gene, FRO2, in transgenic soybean significantly enhances Fe+3 reduction in roots and leaves. Root ferric reductase activity was up to tenfold higher in transgenic plants and was not subjected to post-transcriptional regulation. In leaves, reductase activity was threefold higher in the transgenic plants when compared to control. The enhanced ferric reductase activity led to reduced chlorosis, increased chlorophyll concentration and a lessening in biomass loss in the transgenic events between Fe treatments as compared to control plants grown under hydroponics that mimicked Fe-sufficient and Fe-deficient soil environments. However, the data indicate that constitutive FRO2 expression under non-iron stress conditions may lead to a decrease in plant productivity as reflected by reduced biomass accumulation in the transgenic events under non-iron stress conditions. When grown at Fe(III)-EDDHA levels greater than 10 micromolar, iron concentration in the shoots of transgenic plants was significantly higher than control. The same observation was found in the roots in plants grown at iron levels higher than 32 micromolar Fe(III)-EDDHA. These results suggest that heterologous expression of an iron chelate reductase in soybean can provide a route to alleviate iron deficiency chlorosis.