Sun_2023_Mol.Plant__

Modern semi-dwarf rice varieties of the 'Green Revolution' require a high nitrogen (N) fertilizer supply to obtain a high yield. A better understanding of the interplay between N metabolic and developmental processes is required for improved N use efficiency (NUE) and agricultural sustainability. Here, we show that strigolactones (SLs) modulate root metabolic and developmental adaptations to low N availability, which ensure efficient uptake and translocation of available N. The key repressor DWARF 53 (D53) of the SL signalling interacts with the transcription factor GROWTH-REGULATING FACTOR 4 (GRF4) and prevents GRF4 from binding to its target gene promoters. N limitation induces the accumulation of SLs, which in turn promotes SL-mediated degradation of D53, leading to the release of GRF4 and thus promoting the genes expression associated with N metabolism. N limitation also induces degradation of the rice DELLA protein SLENDER RICE 1 (SLR1) in the D14- and D53-dependent manners, and that is effective for the release of GRF4 from the competitive inhibition caused by SLR1. Our findings reveal a previously unknown mechanism underlying SL and gibberellin crosstalk in response to N availability, which advances our understanding of plant growth-metabolic coordination that can be useful to improve NUE in high-yield crops.