Download MendeleyA milestone in C4 carbon concentration mechanism evolution: structural remodeling of NADP-malic enzyme in Poaceae.
Bohm, J.M., Willms, S., Ferrao, O., Buitrago-Arango, M., Hudig, M., Poschmann, G., Fazelnia, N., Nagel-Steger, L., Klinke, S., Drakonaki, A., Gatsogiannis, C., Tronconi, M.A., Alvarez, C.E., Maurino, V.G.(2026) Mol Biol Evol 43
- PubMed: 42017302 Search on PubMedSearch on PubMed Central
- DOI: https://doi.org/10.1093/molbev/msag056
- Primary Citation Related Structures:
9E6M - PubMed Abstract:
The evolution of C4 photosynthesis required extensive modification of ancestral enzymes enabling the development of an efficient carbon concentrating mechanism. A key example is NADP-malic enzyme (NADP-ME), which, in maize and sorghum-members of the same C4 lineage-underwent gene duplication and neofunctionalization, resulting in 2 plastidic isoforms with distinct oligomeric states: a tetrameric C4-specific isoform and a dimeric housekeeping (nonC4) isoform. In this study, we resolve the structural basis of this oligomeric divergence using X-ray crystallography, cryo-electron microscopy, and molecular modeling combined with targeted biochemical analysis. Our findings demonstrate that the N-terminal region of nonC4-NADP-ME is involved in its oligomeric organization, whereas a suite of adaptive substitutions at the dimer interface drives the transition to the stable tetramer characteristic of the C4 isoform. Moreover, the C-terminal region stabilizes the oligomeric states of C4- and nonC4-NADP-ME through specific interactions with adaptive residues. We propose that tetramerization mitigates aggregation at the high expression levels demanded by the C4 cycle and likely creates a scaffold for the emergence of regulatory properties. Collectively, the data show that remodeling of terminal domains and inter-subunit interfaces rewires the quaternary architecture of the enzymes, illustrating how subtle structural changes can drive the evolution of complex innovations such as C4 photosynthesis.
- Molecular Plant Physiology, Institute for Cellular and Molecular Botany (IZMB), University of Bonn, Kirschallee 1, Bonn 53115, Germany.
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