From Green Revolution to Green Balance: The Nitrogen and Gibberellin Mediated Rice Tiller Growth.

Rice tillering is an important characteristic that responds to both GA (gibberellin) and nitrogen-based fertilizers. How plants balance these two responses? A newly identified NGR5 (NITROGEN-MEDIATED TILLER GROWTH RESPONSE 5) protein reveals its important role in controlling the balance between GA-regulated dwarfism and nitrogen-regulated tillering. NGR5 directly interacts with PRC2 (Polycomb Repressive Complex 2) to form a repressive complex at the shoot branching inhibitory genes in nitrogen-dependent way, thereby repressing branching inhibitors and promoting tillering in response to nitrogen fertilizers. The GA receptor GID1 (GIBBERELLIN INSENSITIVE DWARF1) targets NGR5 for proteolysis by the 26S proteasome. The rice DELLA proteins of GA signaling way competitively inhibit GID1-NGR5 interaction, thereby protecting NGR5 from degradation and enhancing nitrogen-induced tiller number.