A study published in the Journal of Experimental Botany reveals a major challenge in rice biofortification: boosting iron content in the grain can compromise the plant’s ability to tolerate environments where high levels of this metal are present. The research, which utilized CNPEM’s laboratories, was conducted by scientists from Brazilian institutions and led by researchers from the Federal University of Rio Grande do Sul, points to the need to balance nutritional gains with adapting this crop to adverse conditions.
In the study, the researchers used micro X-ray fluorescence to map where iron accumulates in the tissues within the grain of rice, such as the embryo, scutellum and plumule. This type of analysis requires a very bright, coherent light source like the synchrotron in Sirius, CNPEM’s particle accelerator, where the research was conducted by Carlos Pérez, a researcher with the Heterogeneous and Hierarchical Matter Division at the Center’s Brazilian Synchrotron Light National Laboratory.
“We were able to map the distribution of iron and other elements in the rice embryo using the Carnaúba beamline, with subcellular resolution. This allowed us to observe not only the increased concentration of iron within the grains, but also precisely identify in which tissues this nutrient was accumulating, essential information for evaluating biofortification strategies. This level of detail is only possible with a synchrotron light source and a beamline with advanced experimental capabilities,” Pérez explained.
Image obtained using the Carnaúba beamline at Sirius shows the distribution of manganese (green), iron (pink/red) and zinc (blue) in a region of the rice embryo. The image was featured on the cover of the Journal of Experimental Botany.
Rice (Oryza sativa) is a staple food for roughly half the world’s population, but contains low levels of iron; deficiency of this essential nutrient affects millions of people globally. In Brazil, this lack is compensated by the cultural habit of consuming rice together with beans (which are rich in iron), but this is not the case in other countries.
To address this problem, researchers have been exploring biofortification strategies intended to increase the nutrient content of foods. In this study, the scientists investigated the role of two genes, OsVIT1 and OsVIT2, which are responsible for transporting and storing iron in plant cells.
Using genetic modification techniques, the team developed rice plants with both of these genes disabled. The result was a significant increase in iron concentrations in the grains, especially in regions of the embryo such as the scutellum and plumule, indicating changes how the mineral is distributed within the seed.
“It is not enough to boost the concentration of iron in the grain, we must ensure it is in the right place. In rice, we want the iron to reach the endosperm, which is the part eaten in white rice. The analyses using synchrotron light were essential to map this distribution and understand how the genes we studied influence storage of this mineral in the seed,” said Felipe Ricachenevsky, a researcher at the Federal University of Rio Grande do Sul (UFRGS) who carried out the experiments at CNPEM along with fellow researcher Felipe Maraschin.
The data also showed that iron absorption by the roots played an important role in this accumulation, while transport from the leaves was less relevant. Despite the nutritional gains, the modified plants presented a critical problem: greater sensitivity to excess iron in the environment.
This finding reveals a trade-off: a biological conflict between two important objectives, increasing the nutritional value of the food and maintaining the plant’s resistance to stress conditions. This phenomenon is especially relevant because rice is often grown in flooded soils, where iron can accumulate at toxic levels.
The study found that the OsVIT1 and OsVIT2 genes not only limit transport of iron to the grains, but also play an essential role in detoxifying excess iron in the plants.
Additionally, the research utilized advanced techniques like X-ray fluorescence analysis using synchrotron light to map iron distribution in the plant tissues, an important differential for understanding the cellular mechanisms involved.
“Collaboration between different groups was essential for this work. We were able to combine complementary techniques, equipment and knowledge, including the analyses performed at Sirius. This type of infrastructure and scientific connection allows us to answer questions that would be much more difficult to investigate in isolation, and opens up new possibilities for biofortification of rice and other cereals,” added Ricachenevsky.
