Integrative Transcriptomic and Proteomic Analysis Reveals an Alternative Molecular Network of Glutamine Synthetase 2 Corresponding to Nitrogen Deficiency in Rice (<i>Oryza sativa</i> L.)

• Main Authors: Ting Liang, Zhengqing Yuan, Lu Fu, Menghan Zhu, Xiaoyun Luo, Wuwu Xu, Huanran Yuan, Renshan Zhu, Zhongli Hu, Xianting Wu
• Format: Article
• Language: English
• Published: MDPI AG 2021-07-01
• Series: International Journal of Molecular Sciences
• Subjects: rice; root system architecture; transcriptome; proteome; N availability
• Online Access: https://www.mdpi.com/1422-0067/22/14/7674

Nitrogen (N) is an essential nutrient for plant growth and development. The root system architecture is a highly regulated morphological system, which is sensitive to the availability of nutrients, such as N. Phenotypic characterization of roots from LY9348 (a rice variety with high nitrogen use efficiency (NUE)) treated with 0.725 mM NH₄NO₃ (1/4N) was remarkable, especially primary root (PR) elongation, which was the highest. A comprehensive analysis was performed for transcriptome and proteome profiling of LY9348 roots between 1/4N and 2.9 mM NH₄NO₃ (1N) treatments. The results indicated 3908 differential expression genes (DEGs; 2569 upregulated and 1339 downregulated) and 411 differential abundance proteins (DAPs; 192 upregulated and 219 downregulated). Among all DAPs in the proteome, glutamine synthetase (GS2), a chloroplastic ammonium assimilation protein, was the most upregulated protein identified. The unexpected concentration of GS2 from the shoot to the root in the 1/4N treatment indicated that the presence of an alternative pathway of N assimilation regulated by GS2 in LY9348 corresponded to the low N signal, which was supported by GS enzyme activity and glutamine/glutamate (Gln/Glu) contents analysis. In addition, N transporters (<i>NRT2.1</i>, <i>NRT2.2</i>, <i>NRT2.3</i>, <i>NRT2.4</i>, <i>NAR2.1</i>, <i>AMT1.3</i>, <i>AMT1.2</i>, and putative <i>AMT3.3</i>) and N assimilators (<i>NR2</i>, <i>GS1;1</i>, <i>GS1;2</i>, <i>GS1;3</i>, <i>NADH-GOGAT2</i>, and <i>AS2</i>) were significantly induced during the long-term N-deficiency response at the transcription level (14 days). Moreover, the Kyoto Encyclopedia of Genes and Genomes (KEGG) pathway analysis demonstrated that phenylpropanoid biosynthesis and glutathione metabolism were significantly modulated by N deficiency. Notably, many transcription factors and plant hormones were found to participate in root morphological adaptation. In conclusion, our study provides valuable information to further understand the response of rice roots to N-deficiency stress.