Reported by SONG Jianlan
The team unravels how the two competing sides, namely the metabolism promoter GRF4 and the growth inhibitor DELLA, interact with each other and advances to provide a solution to push the balance toward the direction of promoting nitrogen assimilation while maintaining the benefits of dwarfism. (Credit: IGDB)
Application of inorganic nitrogen fertilizers in agriculture production has greatly increased the yield and hence helped enhancing global food security. However, increased application of fertilizers does not necessarily raise the productivity; in fact, the marginal effect produced by fertilizers decreases with the amount of use once it reaches a threshold. On the other hand, excessive use of chemical fertilizers has brought about environmental problems like soil acidification, water eutrophication and extra emissions of house-warming gases.
The key to the solution lies in improving the efficiency of nitrogen fertilizers. A strategy is to breed new crop varieties that are more responsive to nitrogen intake, increasing their production at smaller costs of fertilizers. This, however, demands an in-depth understanding of the inherent mechanisms in the organism that regulate growth, nitrogen assimilation and carbon fixation, and also how they interact with each other to maintain a balance.
The first round of “green revolution” featured the breeding of yield-enhancing semi-dwarf varieties. By introducing a growth inhibitor named DELLA, scientists bred crop varieties that are resistant to lodging, even in the case of intensive nitrogen intake. Every coin has two sides, however. This benefit was acquired at the cost of decreased responsiveness to nitrogen intake. How to break this deadlock has been a headache for biologists.
A team at the CAS Institute of Genetics and Developmental Biology (IGDB) led by Prof. FU Xiangdong successfully broke through. After working for seven years, they successfully identified and extracted from a yield-enhancing rice variety a GROWTH-REGULATING FACTOR 4 (GRF4) transcription factor, and demonstrated that it promotes and integrates nitrogen assimilation, carbon fixation and growth, whereas DELLA inhibits these processes and reduces the efficiency of nitrogen use. They further unraveled how these competing mechanisms interact with each other and maintain a balance, and provided tips on increasing the efficiency of nitrogen use without sacrificing the benefits of dwarfism.
Their research has thus offered a solution for modulating the plant growth and metabolic co-regulation, enabling novel strategies for future sustainable food security. A commentary in Nature remarked that this has blown the horn for a new round of green revolution.
Reference
Shan Li, Yonghang Tian, Kun Wu, Yafeng Ye, Jianping Yu, Jianqing Zhang, Qian Liu, Mengyun Hu, Hui Li, Yiping Tong, Nicholas P. Harberd, Xiangdong Fu*, Modulating Plant Growth–Metabolism Coordination for Sustainable Agriculture. Nature 560, 595-600 (Published: 2018/08/01, 2018). doi: 10.1038/s41586-018-0415-5