Science: Chinese scientists have discovered the molecular mechanism of soybean energy receptors to control symbiotic nitrogen fixation by regulating carbon source allocation

The nodulous symbiotic nitrogen fixation system of legumes and rhizobia is the biological nitrogen fixation system with the highest nitrogen fixation efficiency and the most widely used in agricultural production in nature, which is of great significance
for maintaining primary production and carbon sink in agriculture and natural ecosystems.
The energy consumed by symbiotic nitrogen fixation mainly comes from carbohydrates fixed by photosynthesis, however, the molecular mechanism of how legumes adjust the nitrogen fixation reaction rate of nodules according to the supply of photosynthetic products has yet to be revealed
。 Recently, the research team of Henan University published a research paper entitled "Phosphoenolpyruvate reallocation links nitrogen fixation rates to root nodule energy state" in the journal Science, revealing the molecular mechanism of soybean in response to carbon source supply to regulate nitrogen fixation efficiency of nodules
.

The research team identified a pair of nodular-specific and highly expressed energy receptor proteins GmNAS1 and GmNAP1
in soybeans.
It was found that GmNAS1 could directly bind AMP to form heterodimer on the mitochondrial membrane with GmNAP1, and when the energy state of nodules increased due to increased carbon supply, the AMP content decreased, prompting the dissociation of GmNAS1-GmNAP1 heterodimer to form GmNAS1-GmNAS1-GmNAP1 homodimers.
The homodimer formed afterwards interacts with a transcription factor GmNFYC10a and anchors it to the mitochondria, thereby reducing the level of GmNFYC10a in the nucleus and inhibiting the expression of pyruvate kinase genes, thereby reducing the conversion of phosphoenolpyruvate to pyruvate, and converting more phosphoenolpyruvate to oxaloacetic acid and malic acid, thereby enhancing the carbon source supply of bacterioids and the nitrogen fixation capacity
of nodules.

This study provides an important basis for the design and synthesis of symbiotic nitrogen fixation systems with efficient use of carbon sources, and provides new ideas
for the molecular design of efficient nitrogen fixing crops.