AUTHOR=Huertas Raul , Torres-Jerez Ivone , Curtin Shaun J. , Scheible Wolf , Udvardi Michael 

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

JOURNAL=Frontiers in Plant Science

VOLUME=14

YEAR=2023

URL=https://www.frontiersin.org/journals/plant-science/articles/10.3389/fpls.2023.1211107

DOI=10.3389/fpls.2023.1211107

ISSN=1664-462X

ABSTRACT=<p>Three <italic>PHO2</italic>-like genes encoding putative ubiquitin-conjugating E2 enzymes of <italic>Medicago truncatula</italic> were characterized for potential roles in phosphorous (P) homeostasis and symbiotic nitrogen fixation (SNF). All three genes, <italic>MtPHO2A, B and C</italic>, contain miR399-binding sites characteristic of <italic>PHO2</italic> 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 <italic>MtPHO2B</italic>, in P and N homeostasis. Phenotypic analysis of <italic>pho2</italic> 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, <italic>MtPHO2</italic> genes play roles in systemic and localized, i.e., nodule, P homeostasis affecting SNF.</p>