Genotypic Variation in Spatial Distribution of Fe in Rice Grains in Relation to Phytic Acid Content and Ferritin Gene Expression

Abstract

Rice varieties having high Fe concentration in the endospermic region can be used as a good source for Fe deficit population. In this study, 303 Oryza sativa varieties and 1 Oryza rufipogon accession were assessed for spatial Fe accumulation in grains by Prussian blue staining method. Spatial ferritin protein distribution in grains was visualized by immunohistochemistry, and ferritin expression was assessed in selected rice varieties using semi-quantitative reverse transcription PCR. Three popular rice varieties, namely Sarjoo 52, Madhukar and Jalmagna, and the O. rufipogon variety showed Fe in all the regions of grains, and the highest Fe concentration was observed in the embryo region. Some high-yielding varieties like Swarna, Swarna Sub 1, CSR13 and NDRR359 had lower Fe concentration in the embryo region. The highest Fe concentration was detected in O. rufipogon (49.8 μg/g), followed by Sarjoo 52 (26.1 μg/g) and Madhukar (25.7 μg/g). Phytic acid concentration was the minimum in O. rufipogon (5.75 mg/g) followed by Sarjoo 52 (5.83 mg/g). Western blot and semi-quantitative reverse transcription PCR showed higher expression of ferritin gene in O. rufipogon, Sarjoo 52 and Madhukar. In conclusion, O. rufipogon and Sarjoo 52 had higher Fe concentration in the embryo regions as well as endosperm and aleurone layer, whereas the other varieties had lower Fe concentration in the endosperm. Sarjoo 52 could be used as a donor in the rice breeding program for the generation of new varieties with elevated grain Fe concentration. Keywords: bio-fortification, iron accumulation, ferritin, tissue-specific localization, iron deficit population