Journal Article

PUBDB-2026-01405

http://join2-wiki.gsi.de/foswiki/pub/Main/Artwork/join2_logo100x88.png A milestone in C4 carbon concentration mechanism evolution: structural remodeling of NADP-malic enzyme in Poaceae

Böhm, J. M. ; Willms, S. ; Ferrao, O. ; Buitrago-Arango, M. ; Hüdig, M. ; Poschmann, G. ; Fazelnia, N. ; Nagel-Steger, L. ; Klinke, S. ; Drakonaki, A. ; Gatsogiannis, C. ; Tronconi, M. A. ; Alvarez, C. E. (Corresponding author) ; Maurino, V. G. (Corresponding author)

2026
Oxford Univ. Press Oxford

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Please use a persistent id in citations: doi:10.1093/molbev/msag056  doi:10.3204/PUBDB-2026-01405

Abstract: The evolution of C4 photosynthesis required extensive modification of ancestral enzymes enabling the development of anefficient 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 isoformswith distinct oligomeric states: a tetrameric C4-specific isoform and a dimeric housekeeping (nonC4) isoform. In thisstudy, we resolve the structural basis of this oligomeric divergence using X-ray crystallography, cryo-electronmicroscopy, and molecular modeling combined with targeted biochemical analysis. Our findings demonstrate that theN-terminal region of nonC4-NADP-ME is involved in its oligomeric organization, whereas a suite of adaptive substitutionsat the dimer interface drives the transition to the stable tetramer characteristic of the C4 isoform. Moreover, theC-terminal region stabilizes the oligomeric states of C4- and nonC4-NADP-ME through specific interactions with adaptiveresidues. We propose that tetramerization mitigates aggregation at the high expression levels demanded by the C4 cycleand likely creates a scaffold for the emergence of regulatory properties. Collectively, the data show that remodeling ofterminal domains and inter-subunit interfaces rewires the quaternary architecture of the enzymes, illustrating howsubtle structural changes can drive the evolution of complex innovations such as C4 photosynthesis.

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Contributing Institute(s):

1. EMBL-User (EMBL-User)

Research Program(s):

1. 6G3 - PETRA III (DESY) (POF4-6G3) (POF4-6G3)

Experiment(s):

1. PETRA Beamline P13 (PETRA III)

Appears in the scientific report 2026

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