Modulating plant growth-metabolism coordination for sustainable agriculture.

Abstract

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.