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The Interaction Between PGD2 and G6PD6 Is Involved in Aromatic Amino Acid Synthesis
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School of Applied Biology, Shenzhen City Polytechnic, Shenzhen 518116, China
2
CAS Key Laboratory for Quantitative Engineering Biology, Shenzhen Institute of Synthetic Biology, Shenzhen Institute of Advanced Technology, Chinese Academy of Sciences, Shenzhen 518055, China
3
Shenzhen Key Laboratory of Synthetic Genomics, Guangdong Provincial Key Laboratory of Synthetic Genomics, Key Laboratory of Quantitative Synthetic Biology, Shenzhen Institute of Synthetic Biology, Shenzhen Institute of Advanced Technology, Chinese Academy of Sciences, Shenzhen 518055, China
*
Authors to whom correspondence should be addressed.
Biology 2025, 14(12), 1712; https://doi.org/10.3390/biology14121712
Submission received: 11 November 2025
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Revised: 23 November 2025
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Accepted: 26 November 2025
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Published: 30 November 2025
(This article belongs to the Special Issue Young Researchers in Plant Sciences)
Simple Summary
Plants rely on aromatic amino acids (AAAs) for the synthesis of proteins and secondary metabolites such as flavonoids and auxins. The oxidative pentose phosphate (OPP) pathway provides the shikimate pathway with the key precursor erythrose-4-phosphate (E4P) and the reducing equivalent NADPH, but the regulatory association between these two pathways has rarely been reported. This study confirmed that glucose-6-phosphate dehydrogenase 6 (G6PD6) and 6-phosphogluconate dehydrogenase 2 (PGD2), the rate-limiting enzymes in the OPP pathway, exhibit a co-expression pattern and interact directly; overexpression of either gene in the AAA synthesis-deficient arogenate dehydrogenase 2 (adh2) mutant partially rescued the mutant’s nutritional deficiency phenotype. This finding clarifies the molecular mechanism by which G6PD6 and PGD2 synergistically participate in AAA synthesis and provides an important experimental basis for deciphering the regulatory network of plant AAA metabolism.
Abstract
The biosynthesis of AAAs in plants primarily relies on the shikimate pathway, with metabolic flux sustained by NADPH and E4P generated via the OPP pathway. However, how OPP enzymes coordinate to support AAA production remains unclear. Here, we investigated the direct interaction between two consecutive NADPH-producing enzymes, G6PD6 and PGD2, and its role in metabolic coupling. Using BiFC, Co-IP, pull-down assays, and domain mapping, we showed that G6PD6 and PGD2 form a cytosolic protein complex via the C-terminal domain of PGD2. Structural modeling identified potential interaction residues: PHE294, GLY297, and LEU298 in PGD2, and GLY351, LYS499, and ALA500 in G6PD6. Overexpression of either enzyme partially rescued the dwarf phenotype of adh2 mutants caused by AAA deficiency. These findings indicate that the PGD2–G6PD6 complex coordinates OPP-derived reductive power and carbon flux to support downstream AAA biosynthesis. This study reveals a functional link between OPP enzyme interactions and AAA production, suggesting that metabolic flux can be regulated through direct enzyme–enzyme association. Future work will explore how this complex responds to metabolic demand and whether additional components contribute to coordinating flux between the OPP and shikimate pathways.
