Functional analysis of transgenic rice (Oryza sativa L.) transformed with an Arabidopsis thaliana ferric reductase (AtFR02)

Iron deficient soils limit crop production on 25-30% of the world's arable land. Both grasses (Strategy 11) and dicotyledonous crops (Strategy 1) are susceptible to iron deficiency, but each respond to iron stress by different mechanisms. In order to acquire iron from the soil, Strategy I plants utilize an iron reduction and Fe2+ transporter system at the root level, whereas Strategy 11 plants use a phytosiderophore-based system. Unfortunately, in some grasses such as rice, the production of phytosiderophores is low, and thus their ability to survive in iron-deficient conditions is limited. To determine whether a Strategy I root reductase can function in a Strategy 11 plant, and enhance its iron acquisition, we inserted the FRO2 gene from Arabidopsis thaliena (AtFR02) into rice (Oryza sativa). Root reductase activity was determined and was found to be low in both transgenic and control plants grown at different iron concentrations. The low activity levels were attributed to the release of soluble reductants in the assay and not to membrane-localized root reductase activity. RT-PCR analysis of rice roots and shoots of plants grown hydroponically at different iron concentrations revealed no expression of the transgene. In this paper, we discuss the lack of functionality of the AtFRO2 gene in rice, and we perform a comparative study of the 0.6 kb promoter region by PlantCARE and PLACE analysis.