Figure 9.

Model of GmNAC–GmCYP regulation of nodule senescence. Chlorophyll degradation and decreased photosynthesis are hallmarks of leaf senescence. In nodules, the amount of leghemoglobin is an indicator of nitrogen-fixation ability. When soybean is at the full bloom stage, the nodules undergo extensive senescence along with a reduction in nitrogen-fixation capacity. Some NAC transcription factors, including GmNAC039 and GmNAC018, are significantly induced during nodule senescence. This model proposes that GmNAC039/018 may activate downstream SAG expression to promote nodule senescence in soybean.