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

Raul Huertas; Ivone Torres-Jerez; Shaun J Curtin; Wolf Scheible; Michael Udvardi

doi:10.3389/fpls.2023.1211107

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

Front Plant Sci. 2023 Jun 13:14:1211107. doi: 10.3389/fpls.2023.1211107. eCollection 2023.

Authors

Raul Huertas¹, Ivone Torres-Jerez¹, Shaun J Curtin^{2

3

4

5}, Wolf Scheible¹, Michael Udvardi¹

Affiliations

¹ Noble Research Institute LLC, Ardmore, OK, United States.
² United States Department of Agriculture, Plant Science Research Unit, St. Paul, MN, United States.
³ Department of Agronomy and Plant Genetics, University of Minnesota, St. Paul, MN, United States.
⁴ Center for Plant Precision Genomics, University of Minnesota, St. Paul, MN, United States.
⁵ Center for Genome Engineering, University of Minnesota, St. Paul, MN, United States.

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, B and 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.

Keywords: Medicago truncatula; PHO2; nitrogen; phosphorus; symbiotic nitrogen fixation (SNF).

Grants and funding

This work was supported by the Noble Research Institute LLC. Noble Research Institute was not involved in the study design, collection, analysis, interpretation of data, the writing of this article, or the decision to submit it for publication. SJC was supported by the U.S. Department of Agriculture, Agricultural Research Service. Mention of any trade names or commercial products in this article is solely for the purpose of providing specific information and does not imply recommendation or endorsement by the U. S. Department of Agriculture. USDA is an equal opportunity provider and employer, and all agency services are available without discrimination.