AUTHOR=Chen Haifei , Lv Wei , Zhang Wenqi , Zhao Jie , Zhang Quan , Zhang Zhenhua TITLE=Integrated comparative transcriptome and physiological analysis reveals the metabolic responses underlying genotype variations in NH4+ tolerance JOURNAL=Frontiers in Plant Science VOLUME=14 YEAR=2023 URL=https://www.frontiersin.org/journals/plant-science/articles/10.3389/fpls.2023.1286174 DOI=10.3389/fpls.2023.1286174 ISSN=1664-462X ABSTRACT=

Several mechanisms have been proposed to explain NH4+ toxicity. However, the core information about the biochemical regulation of plants in response to NH4+ toxicity is still lacking. In this study, the tissue NH4+ concentration is an important factor contributing to variations in plant growth even under nitrate nutrition and NH4+ tolerance under ammonium nutrition. Furthermore, NH4+ led to the reprogramming of the transcriptional profile, as genes related to trehalose-6-phosphate and zeatin biosynthesis were downregulated, whereas genes related to nitrogen metabolism, camalexin, stilbenoid and phenylpropanoid biosynthesis were upregulated. Further analysis revealed that a large number of genes, which enriched in phenylpropanoid and stilbenoid biosynthesis, were uniquely upregulated in the NH4+- tolerant ecotype Or-1. These results suggested that the NH4+-tolerant ecotype showed a more intense response to NH4+ by activating defense processes and pathways. Importantly, the tolerant ecotype had a higher 15NH4+ uptake and nitrogen utilization efficiency, but lower NH4+, indicating the tolerant ecotype maintained a low NH4+ level, mainly by promoting NH4+ assimilation rather than inhibiting NH4+ uptake. The carbon and nitrogen metabolism analysis revealed that the tolerant ecotype had a stronger carbon skeleton production capacity with higher levels of hexokinase, pyruvate kinase, and glutamate dehydrogenase activity to assimilate free NH4+, Taken together, the results revealed the core mechanisms utilized by plants in response to NH4+, which are consequently of ecological and agricultural importance.