Natural Allelic Variation Improves Nitrogen Use Efficiency in Rice

Zhang, Zhu, Shen, Ji et al. discover a way to enhance nitrogen use efficiency and grain yield in rice. The Plant Cell (2020)

 Background: Nitrogen (N), an essential element for crop growth, is provided to plants by external fertilizer application. However, the excessive use of N fertilizers increases the cost of agricultural production and causes a series of environmental problems including climate change, soil acidification, and water eutrophication. Therefore, improving crop N use efficiency (NUE) is an urgent goal of modern agriculture. Plant N metabolism is known to be regulated by multiple plant hormones including auxin. Nevertheless, the identities of the auxin-related genes involved in this regulation and how they can be exploited to enhance crop NUE and yield remain largely elusive.

Question: We wanted to know how qDNR1 (Dull Nitrogen Response 1), a NUE-related quantitative trait locus (QTL) identified in rice, modulates N metabolism by regulating auxin homeostasis and whether manipulating DNR1 levels in this crop could improve NUE and crop yields.

Findings: qDNR1 is a QTL responsible for the differences in N uptake and assimilation activities between indica and japonica rice varieties. DNR1 is a negative regulator of auxin accumulation that is itself regulated by external N conditions. Indica rice varieties generally contain lower DNR1 levels than japonica rice, providing them with higher auxin contents. This, in turn, leads to increased NUE and grain yield by activating multiple AUXIN RESPONSE FACTORs. Finally, we suggest that increasing the auxin contents in japonica varieties by reducing their DNR1 levels could improve their NUE and grain yield.

Next steps: Our findings suggest that modulating the N-DNR1-mediated auxin response could be used to improve rice yield in an environmentally sustainable manner. How this breeding strategy could be implemented will be the focus of future studies. In addition, the mechanism underlying how N increases DNR1 levels would be worth exploring in the future.

Siyu Zhang, Limei Zhu, Chengbo Shen, Zhe Ji, Haipeng Zhang, Tao Zhang, Yu Li, Jianping Yu, Ning Yang, Yubing He, Yanan Tian, Kun Wu, Juyou Wu, Nicholas P. Harberd, Yunde Zhao, Xiangdong Fu, Shaokui Wang, Shan Li (2021). Natural Allelic Variation in a Modulator of Auxin Homeostasis Improves Grain Yield and Nitrogen Use Efficiency in Rice. Plant Cell