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ARS Home » Midwest Area » St. Paul, Minnesota » Plant Science Research » Research » Publications at this Location » Publication #404234

Research Project: Functional Genomics for Improving Nutrients and Quality in Alfalfa and Soybean

Location: Plant Science Research

Title: Medicago truncatula PHO2 genes have distinct roles in phosphorus homeostasis and symbiotic nitrogen fixation

item HUERTAS, RAUL - Noble Research Institute
item TORRES-JEREZ, IVONE - Noble Research Institute
item Curtin, Shaun
item SCHEIBLE, WOLF - Noble Research Institute
item UDVARDI, MICHAEL - Noble Research Institute

Submitted to: Frontiers in Plant Science
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 5/22/2023
Publication Date: 6/13/2023
Citation: Huertas, R., Torres-Jerez, I., Curtin, S.J., Scheible, W., Udvardi, M. 2023. Medicago truncatula PHO2 genes have distinct roles in phosphorus homeostasis and symbiotic nitrogen fixation. Frontiers in Plant Science. 14.

Interpretive Summary: Plants use several strategies to enhance phosphate (P) uptake under P-limited conditions. An important gene involved in the regulation of P uptake is PHO2. To date, PHO2 has only been characterized in the model plant Arabidopsis and little is known about its function in crop plants. Three PHO2 genes, PHO2-A, -B and -C, were identified in the legume Medicago truncatula. By examining plants in which one of each of the three genes was mutated and not expressed, PHO2-B was found to maintain whole-plant P equilibrium under sufficient P supply while PHO2-C maintains P under P-deficient conditions. PHO2-A has a unique role in maintaining P equilibrium in the nitrogen-fixing root nodule. These results help shed light on the important roles that PHO2 genes play in coordinating both whole-plant P and N equilibrium that are fundamental to sustaining plant growth.

Technical Abstract: Three PHO2-like genes encoding putative ubiquitin-conjugating E2 enzymes of Medicago truncatula were characterized for potential roles in phosphorous (P) homeostasis and symbiotic nitrogen fixation (SNF). All three genes, MtPHO2A-C, contain miR399-binding sites characteristic of PHO2 genes in other plant species. Distinct spatiotemporal expression patterns and responsiveness of gene expression to P- and N-deprivation in roots and shoots indicated potential roles, especially for MtPHO2B, in P and N homeostasis. Phenotypic analysis of pho2 mutants revealed that MtPHO2B is integral to Pi homeostasis, affecting Pi allocation during plant growth under nutrient-replete conditions, while MtPHO2C had a limited role in controlling Pi homeostasis. Genetic analysis also revealed a connection between Pi allocation, plant growth and SNF performance. Under N-limited, SNF conditions, Pi allocation to different organs was dependent on MtPHO2B and, to a lesser extent, MtPHO2C and MtPHO2A. MtPHO2A also affected Pi homeostasis associated with nodule formation. Thus, MtPHO2 genes play roles in systemic and localized, i.e., nodule, P homeostasis affecting SNF.