One versus many independent assemblies of symbiotic nitrogen fixation in flowering plants

• Published in: Nature communications Vol. 16; no. 1; pp. 5345 - 13
• Main Authors: Doyle, Jeff J., Ren, Jian, Pawlowski, Katharina, James, Euan K., Gao, Yingzhi
• Format: Journal Article
• Language: English
• Published: London Nature Publishing Group UK 19.06.2025; Nature Publishing Group; Nature Portfolio
• Subjects: 631/181/735; 631/449/2669; Bacteria; Crops; Divergence; Fabaceae - genetics; Fabaceae - microbiology; Flowering; Flowering plants; Humanities and Social Sciences; Hypotheses; Legumes; Magnoliophyta; Magnoliopsida - genetics; Magnoliopsida - microbiology; multidisciplinary; Mycorrhizae; Nitrogen; Nitrogen fixation; Nitrogen Fixation - genetics; Nitrogen Fixation - physiology; Nitrogen-fixing bacteria; Nitrogenation; Nodulation; Nodules; Origins; Perspective; Phylogeny; Plant Root Nodulation - genetics; Plant structures; Plants (botany); Root Nodules, Plant - microbiology; Science; Science (multidisciplinary); Symbiosis; Symbiosis - physiology
• ISSN: 2041-1723; 2041-1723
• DOI: 10.1038/s41467-025-60433-w

Some species of legumes and nine other flowering plant families form symbioses with bacteria that fix atmospheric nitrogen within specialized plant structures called nodules. How and how often nodulation symbiosis originated has implications for engineering symbiotic nitrogen fixation in non-legume crops. The prevailing hypothesis of a single origin with massive parallel losses has been challenged in a phylogenomic study favoring 16 origins and 10 losses. Nodulation has been assembled once or many times from existing processes (e.g., mycorrhizal symbiosis) and therefore almost nothing about it is truly novel. Because any feature of nodulation can be explained either as divergence from a common origin or as convergence in unrelated taxa, tests are needed that can distinguish whether assembly of homologous components has occurred uniquely or convergently. Much needs to be learned about nodulation symbioses across the proposed independent origins, especially involving the master nodulation transcription factor, Nodule Inception ( NIN ). Symbiosis of nitrogen-fixing bacteria in evolutionarily novel “nodules” of diverse flowering plants including legume crops was assembled from pre-existing functions. Testing hypotheses of single vs. multiple origins is the focus of this Perspective.