Discovering the genetic mechanisms underlying the establishment of the legume-rhizobia symbiosis under phosphate-deficient conditions

• Applicant: Dr. Martina Ried-Lasi
• Subject Area: Organismic Interactions, Chemical Ecology and Microbiomes of Plant Systems ; Plant Physiology
• Term: since 2025
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 547682164

Phosphorus, an essential macronutrient, plays a crucial role in the biosynthesis of various biological molecules and in decoding environmental cues through phosphorylation and dephosphorylation cascades. Plants uptake phosphorus as inorganic phosphate (Pi), which, however, is present in limited quantities in many arable soils worldwide. Legumes can form root nodule symbioses with nitrogen-fixing bacteria called rhizobia. Pi deficiency negatively impacts plant growth and yield, and compromises nitrogen fixation by reducing the number of formed root nodules. The genetic mechanisms governing the establishment of root nodule symbiosis under Pi-limiting conditions have remained largely unexplored. Given that Pi deficiency is an abiotic stressor to which most crops are exposed, and root nodule symbiosis is crucial for delivering reduced nitrogen to the food chain, it is imperative to decipher the genetic mechanisms underlying the establishment of root nodule symbiosis under Pi deficiency. The main objectives of this collaborative project are (I) to identify symbiotic genes whose expression is modulated by Pi deficiency, (II) to investigate the how the transcription factor PHR1 and autoregulatory mechanisms control root nodule symbiosis under Pi deficiency and collaborate, and (III) to determine the direct targets of PHR1 in the symbiosis between legumes and rhizobia. To achieve these goals, we will use the model legume Lotus japonicus and the agriculturally relevant crop legume Phaseolus vulgaris. This research project will deepen our understanding of the genetic basis of root nodule symbiosis under Pi deficiency and facilitate the transfer of results to other important crops. The project will be conducted by the Ried-Lasi (Germany) and Valdés-López (Mexico) research groups. The Ried-Lasi group has comprehensive expertise in studying the interaction between plant roots and beneficial microbes in L. japonicus, as well as in investigating PHR1-DNA interactions. The Valdés-López group has extensive experience in researching the genetic regulation (e.g. via PHR1 and autoregulation) of root nodule symbiosis in P. vulgaris. The complementary expertise of both labs will generate strong synergistic effects, enabling an understanding of the genetic regulation of root nodule symbiosis under Pi deficiency. Ultimately, the knowledge gained in this study will contribute to developing more resilient legume varieties capable of thriving in Pi-poor soils, thereby enhancing agricultural sustainability and food security.

• DFG Programme: Research Grants
• International Connection: Mexico
• Partner Organisation: Universidad Nacional Autónoma de México (UNAM)
• Cooperation Partner: Professor Dr. Oswaldo Valdés-López