PhD student Agricultural Biotechnology Research Center, Academia Sinica Taipei City, Taipei, Taiwan (Republic of China)
Body of Abstract: The rice ecosystem varies from lowland (flooded) to upland (aerobic) conditions. However, in aerobic conditions, the rice has poor growth which might be due to the dramatic reduction of iron (Fe) bioavailability. Contrastingly, plants like barley are tolerant to Fe-deficient conditions. The synthesis and secretion of specific compounds (higher phytosiderophores; mugineic acid) in barley solubilize Fe in the rhizosphere more efficiently which could not be found in rice. To address Fe deficiency in upland conditions, we studied the homologs of the barley enzyme, Iron Deficiency Specific (IDS), responsible for the production of higher phytosiderophores in rice. Interestingly, the homologs are discovered in domesticated and wild rice but not in ancient wild rice. Ancient wild rice used to grow in deep swamps and does not need the enzyme. While wild rice and its domesticated varieties started growing in aerobic conditions and during the course of evolution, might have evolved the enzyme. This suggested the evolutionary role of the enzyme in Fe uptake under aerobic conditions. To further understand the role of the enzyme in rice, we created transgenic lines with induced expression of the enzyme in rice plants. The transgenics are resistant to Fe-deficient conditions indicated by plant health. The study of transgenic lines further revealed that the mode of action of the enzyme is not the same as the barley enzyme. These transgenics show induced Fe deficiency responsive metabolite content. The change in metabolite content is not due to the transcription regulation of the responsive genes but metabolic consequences. The study indicates the enzyme role in specific unknown reactions to enhance Fe solubility in the soil for plant uptake. The development of new rice varieties with the modulation of this enzyme has great potential in Fe-deficient conditions and may lead to a healthy crop in aerobic/ upland conditions.