ZmNF-YC1-ZmAPRG pathway modulates low phosphorus tolerance in maize.

Phosphorus (P) is an essential nutrient for plant growth and yield. Low phosphate-use-efficiency makes it important to clarify the molecular mechanism of low phosphorus stress. In our previous studies, a phosphorus efficiency gene ZmAPRG was identified. Here, we further screened the upstream regulator ZmNF-YC1 of ZmAPRG by yeast one hybrid (Y1H) assay, and found it was a low Pi-inducible gene. The results of dual luciferase assays, expression analysis and ChIP-qPCR assays showed that ZmNF-YC1 is a positive regulator of ZmAPRG. Overexpression of ZmNF-YC1 improved low phosphorus tolerance whereas knockout of ZmNF-YC1 decreased low phosphorus tolerance in maize. Bimolecular fluorescence complementation (BiFC), Y2H and Y3H assay further showed that ZmNF-YC1 can interact with ZmNF-YB14, and recruit ZmNF-YA4/10 to form NF-Y complexes. Transcriptional activation assay confirmed that the NF-Y complexes can activate the promoters of ZmAPRG. Meanwhile, transcriptome and metabolome analyses indicated that overexpression of ZmAPRG improves low P tolerance by regulating lipid composition and photosynthetic capacity, and chlorophyll fluorescence parameters supplied evidence in support of this hypothesis. Furthermore, overexpression of ZmAPRG increased grain yield in inbred and hybrid maize under low P conditions. Taken together, our research revealed the low P tolerance mechanism of ZmNF-YC1-ZmAPRG pathway.