Prasanna Jangam Annie, Mandal Vikas Kumar, Kumar Dinesh, Chakraborty Navjyoti, Raghuram Nandula
Centre for Sustainable Nitrogen and Nutrient Management, School of Biotechnology, Guru Gobind Singh Indraprastha University, Sector 16C, Dwarka, New Delhi, 110078, India.
Prof. H.S. Srivastava Foundation for Science and Society, 10B/7, Madan Mohan Malviya Marg, Lucknow, India.
Plant Cell Rep. 2023 Dec;42(12):1987-2010. doi: 10.1007/s00299-023-03078-7. Epub 2023 Oct 24.
Nitrate-responsive transcriptomic, phenotypic and physiological analyses of rice RGA1 mutant revealed many novel RGA1-regulated genes/processes/traits related to nitrogen use efficiency, and provided robust genetic evidence of RGA1-regulation of NUE. Nitrogen (N) use efficiency (NUE) is important for sustainable agriculture. G-protein signalling was implicated in N-response/NUE in rice, but needed firm genetic characterization of the role of alpha subunit (RGA1). The knock-out mutant of RGA1 in japonica rice exhibited lesser nitrate-dose sensitivity than the wild type (WT), in yield and NUE. We, therefore, investigated its genomewide nitrate-response relative to WT. It revealed 3416 differentially expressed genes (DEGs), including 719 associated with development, grain yield and phenotypic traits for NUE. The upregulated DEGs were related to photosynthesis, chlorophyll, tetrapyrrole and porphyrin biosynthesis, while the downregulated DEGs belonged to cellular protein metabolism and transport, small GTPase signalling, cell redox homeostasis, etc. We validated 26 nitrate-responsive DEGs across functional categories by RT-qPCR. Physiological validation of nitrate-response in the mutant and the WT at 1.5 and 15 mM doses revealed higher chlorophyll and stomatal length but decreased stomatal density, conductance and transpiration. The consequent increase in photosynthesis and water use efficiency may have contributed to better yield and NUE in the mutant, whereas the WT was N-dose sensitive. The mutant was not as N-dose-responsive as the WT in shoot/root growth, productive tillers and heading date, but equally responsive as WT in total N and protein content. The RGA1 mutant was less impacted by higher N-dose or salt stress in terms of yield, protein content, photosynthetic performance, relative water content, water use efficiency and catalase activity. PPI network analyses revealed known NUE-related proteins as RGA1 interactors. Therefore, RGA1 negatively regulates N-dose sensitivity and NUE in rice.
水稻RGA1突变体的硝酸盐响应转录组学、表型和生理分析揭示了许多与氮利用效率相关的、受RGA1调控的新基因/过程/性状，并为RGA1对氮利用效率的调控提供了有力的遗传学证据。氮（N）利用效率（NUE）对可持续农业很重要。G蛋白信号传导与水稻的氮响应/氮利用效率有关，但需要对α亚基（RGA1）的作用进行确凿的遗传学表征。粳稻中RGA1的敲除突变体在产量和氮利用效率方面表现出比野生型（WT）更低的硝酸盐剂量敏感性。因此，我们研究了其相对于WT的全基因组硝酸盐响应。结果揭示了3416个差异表达基因（DEG），其中719个与氮利用效率的发育、籽粒产量和表型性状相关。上调的DEG与光合作用、叶绿素、四吡咯和卟啉生物合成有关，而下调的DEG属于细胞蛋白质代谢和运输、小GTPase信号传导、细胞氧化还原稳态等。我们通过RT-qPCR验证了26个跨功能类别的硝酸盐响应DEG。在1.5和15 mM剂量下对突变体和WT的硝酸盐响应进行生理验证，结果显示叶绿素和气孔长度增加，但气孔密度、导度和蒸腾作用降低。光合作用和水分利用效率的相应提高可能有助于突变体获得更好的产量和氮利用效率，而WT对氮剂量敏感。突变体在地上部/根部生长、有效分蘖和抽穗期方面对氮剂量的响应不如WT，但在总氮和蛋白质含量方面与WT的响应相同。就产量、蛋白质含量、光合性能、相对含水量、水分利用效率和过氧化氢酶活性而言，RGA1突变体受高氮剂量或盐胁迫的影响较小。蛋白质-蛋白质相互作用（PPI）网络分析揭示了已知的与氮利用效率相关的蛋白质作为RGA1相互作用因子。因此，RGA1对水稻中的氮剂量敏感性和氮利用效率起负调控作用。
