Effects of Nitrogen Deficiency on the Metabolism of Organic Acids and Amino Acids in Oryza sativa

Ling-Hua Chen; Zu-Xin Cheng; Ming Xu; Zhi-Jian Yang; Lin-Tong Yang

doi:10.3390/plants11192576

Effects of Nitrogen Deficiency on the Metabolism of Organic Acids and Amino Acids in Oryza sativa

Plants (Basel). 2022 Sep 29;11(19):2576. doi: 10.3390/plants11192576.

Authors

Ling-Hua Chen¹, Zu-Xin Cheng², Ming Xu², Zhi-Jian Yang^{2

3}, Lin-Tong Yang⁴

Affiliations

¹ College of Jinshan, Fujian Agriculture and Forestry University, Fuzhou 350002, China.
² Fujian Engineering Technology Research Center of Breeding and Utilization for Special Crops, College of Agriculture, Fujian Agriculture and Forestry University, Fuzhou 350002, China.
³ Key Laboratory of Crop Biotechnology, College of Agriculture, Fujian Agriculture and Forestry University, Fuzhou 350002, China.
⁴ College of Resources and Environment, Fujian Agriculture and Forestry University, Fuzhou 350002, China.

Abstract

Organic acids metabolism and nitrogen (N) metabolism in rice seedlings and the relationship between them are not fully understood. In this study, rice (Oryza sativa L. ssp. Indica) variety "Huanghuazhan" was used as the experimental material, and three N levels (5 mM, 1 mM, and 0 mM NH₄NO₃) were set by the hydroponic method for different levels of N treatment. Our results showed that the increased content of malate in rice leaves caused by reducing N level was related to the increased synthesis of malate (the activity of leaf PEPC increased)and the decreased degradation of malate (the activity of leaf NADP-ME decreased), while the increased contents of citrate and isocitrate in rice leaves caused by reducing N level might not be caused by the increased biosynthesis, but due to the decrease in degradation of citrate and isocitrate (the activities of leaf CS, ACO, and NADP-IDH decreased). The increased content of malate in rice roots caused by reducing N level might be related to the increased biosynthesis and the decreased degradation of root malate (the activities of root NAD-MDH and PEPC increased, while the activity of NADP-ME decreased). Compared to the control (5 mM NH₄NO₃), the increased content of citrate in rice roots caused by reducing N level might be related to the increased biosynthesis rather than the decreased degradation of citrate, due to the higher activities of CS and ACO in rice roots under 0 mM N and 1mM N treatment when compared to that of the control ones. At the same time, the increased content of isocitrate in roots was related to the increased isomerization of isocitrate (the activity of root ACO increased) and the decreased degradation of isocitrate (the activity of root NADP-IDH decreased). With the reducing N level, the activities of N metabolism-related enzymes, such as nitrate reductase (NR), glutamine synthetase (GS), and glutamate synthase (GOGAT), decreased in rice leaves and roots, resulting in the decreased contents of total free amino acids (TFAAs) and soluble proteins in rice seedlings, and finally led to the growth inhibition. Our results showed that the dynamics of organic acids metabolism caused by reducing N level were different in rice leaves and roots. In conclusion, there was a close correlation between organic acids metabolism and N metabolism in rice leaves and roots under N-limited conditions; furthermore, such a correlation was more obvious in rice leaves than that of roots.

Keywords: growth; nitrogen deficiency; nitrogen metabolism; organic acid; rice.

Abstract

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