Modulating plant growth-metabolism coordination for sustainable agriculture

Enhancing future global food security by increasing cereal Green Revolution Variety (GRV) productivity risks escalating collateral environmental damage from inorganic nitrogen (N) fertilizers. Whilst crop N use-efficiency (NUE) improvements are therefore essential, they require in-depth understanding of unknown co-regulatory mechanisms integrating growth, N assimilation and carbon (C) fixation. Here we show that the balanced opposing activities and physical interactions of the rice GROWTH-REGULATING FACTOR 4 (OsGRF4) transcription factor and the DELLA growth-inhibitor confer homeostatic co-regulation of growth, C and N metabolism. OsGRF4 promotes and integrates N assimilation, C fixation and growth, whilst DELLA inhibits them. In consequence, the DELLA accumulation characteristic of GRVs confers yield-enhancing dwarfism, but also reduces NUE. However, GRV NUE and grain yield are increased by tipping the OsGRF4-DELLA balance towards increased OsGRF4 abundance. Modulation of plant growth and metabolic co-regulation thus enables novel breeding strategies for future sustainable food security and a new Green Revolution.