Generation and Field Trials of Transgenic Rice Tolerant to Iron Deficiency

Iron deficiency is a major cause of reduced crop yields worldwide, particularly in calcareous soils. Unlike barley, rice is highly susceptible to iron deficiency because of a low capacity to secrete mugineic acid family phytosiderophores (MAs), which are iron chelators secreted by graminaceous plants. We present an approach toward the generation along with field trials of transgenic rice lines exhibiting increased tolerance to iron deficiency. Cloning barley genes that encode biosynthetic enzymes for MAs enabled us to produce transgenic rice plants by introducing barley MAs biosynthesis-related genes. We tested three transgenic lines possessing barley genomic fragments responsible for MAs biosynthesis in a paddy field experiment on calcareous soil, which revealed tolerance of these lines to low iron availability. We also applied new approaches to generate iron-deficiency-tolerant rice lines, including the introduction of an engineered ferric-chelate reductase gene and manipulation of transcription factor genes regulating the iron deficiency response.