Symbioprotein Ferritin (SymProFerr)

Some plants can protect themselves from dehydration by communicating with bacteria in the soil. This increased drought tolerance can protect and maintain the yield production during low rainfall and/or increasing temperatures. The positive interrelationship (symbiosis) between legume plants (e.g. peas and beans) with special soil bacteria (rhizobia) was first described about 130 years ago. It allows these plants to grow in nitrogen-poor soil while supplying the bacteria with sugar and other nutrients. In this symbiosis, a new plant organs, the root nodules are formed in which the bacteria can live. This subsequently creates many changes in the plant`s metabolism that can have a positive effect on their immune system. However, there are still many unanswered questions about how this symbiosis is formed, which nutrients are particularly important, how the nutrient exchange works and why the plant becomes more resilient as a result. Iron is one of the nutrients that seems to be important not only for the growth of plants, but also for the formation and function of the symbiosis. The plant protein ferritin is used for the targeted storage and release of iron throughout the plant tissues, and during the symbiosis to the root nodules as well. Initial results showed that plants lacking this particular protein cannot develop root nodules, suggesting that ferritin is also important for the development of symbiosis. Interestingly, ferritin also seems to be involved in the increased tolerance to drought in the plants while beeing enhanced during symbiosis. In our study, therefore, the dual role of ferritin and iron both in the formation of symbiosis and in reducing drought stress will be examined and ultimately understood. The findings are likely to be transferable to many important crop plants of the legume family. Plant breeders could use this knowledge to protect their legumes from climate change.

This research project builds upon our previous findings on improved drought stress tolerance in legumes through their symbiotic partnership with rhizobia (FWF [P23441-B20]). Rhizobia enable legumes to grow on nitrogen-poor soils without the need for fertilization. In this study, we identified a specific group of proteins, known as ferritins, as crucial regulators. Ferritins are proteins that play a central role in regulating iron homeostasis not only in the human body but also in plants. Iron can be harmful at high concentrations and is released under stress conditions. Ferritins preventing damage caused by excess iron. Our investigations revealed that ferritins are induced in symbiotic plants and may play a key role in enhanced drought stress tolerance. Since there are multiple types of ferritin proteins, it was important to determine which of these proteins plays the main role both in symbiosis with rhizobia and in drought stress tolerance. Results Our team was able to analyze for the first time the distribution of different ferritins across various organs of legumes and identify which ferritin plays a primary role in nodules versus leaves: Nodule Formation: We demonstrated for the first time that a specific ferritin is essential for nodule formation and thus for symbiosis. Without this protein, nodules do not form - a critical process enabling growth on nitrogen-poor soils. Drought Stress Tolerance: During symbiosis, another ferritin increases in leaf tissue, enhancing the plant's drought stress tolerance. The Result demonstrates a universal benefit that transcends the genetic variability of different natural accessions. Based on these findings, we now refer to ferritins as "Symbioproteins." The analysis was successfully applied to two different plant species-both under controlled laboratory conditions and in field studies conducted at Lake Neusiedl (Burgenland, Austria). Our research contributes significantly to understanding the symbiosis between legumes and rhizobia as well as improving drought stress tolerance-both critical topics for sustainable agriculture. The scientific findings from this project will be published as peer-reviewed articles: 1. Symbioprotein Ferritin - Evidence for a dual role of Ferritin(s) in legume-rhizobium symbiosis 2. Symbiont Induced Staygreen effect is robust across different natural accessions of Medicago truncatula, independent of their inherited drought stress tolerance 3. The role of Ferritin in Lotus tenuis grown at different sites at the salt lake Neusiedl Further information on our project website: https://homepage.univie.ac.at/stefanie.wienkoop/SYMPROFERR_abstract_en.html. This project benefited from collaborations: Data for the first publication were generated jointly with Prof. Gonzalez-Guerrero (Technical University of Madrid). Results from the third publication were obtained through collaboration with Prof. Woebke and PhD student Dania Randi (FWF DocSchool Maintain).