Sun Li, Di Dongwei, Li Guangjie, Kronzucker Herbert J, Shi Weiming
State Key Laboratory of Soil and Sustainable Agriculture, Institute of Soil Science, Chinese Academy of Sciences, Nanjing 210008, China.
Department of Biological Sciences, University of Toronto, 1265 Military Trail, Toronto, ON, M1C 1A4, Canada; School of BioSciences, The University of Melbourne, Parkville, VIC 3010, Australia.
J Plant Physiol. 2017 May;212:94-104. doi: 10.1016/j.jplph.2017.02.006. Epub 2017 Feb 22.
Ammonium (NH) is the predominant nitrogen (N) source in many natural and agricultural ecosystems, including flooded rice fields. While rice is known as an NH-tolerant species, it nevertheless suffers NH toxicity at elevated soil concentrations. NH excess rapidly leads to the disturbance of various physiological processes that ultimately inhibit shoot and root growth. However, the global transcriptomic response to NH stress in rice has not been examined. In this study, we mapped the spatio-temporal specificity of gene expression profiles in rice under excess NH and the changes in gene expression in root and shoot at various time points by RNA-Seq (Quantification) using Illumina HiSeqTM 2000. By comparative analysis, 307 and 675 genes were found to be up-regulated after 4h and 12h of NH exposure in the root, respectively. In the shoot, 167 genes were up-regulated at 4h, compared with 320 at 12h. According to KEGG analysis, up-regulated DEGs mainly participate in phenylpropanoid (such as flavonoid) and amino acid (such as proline, cysteine, and methionine) metabolism, which is believed to improve NH stress tolerance through adjustment of energy metabolism in the shoot, while defense and signaling pathways, guiding whole-plant acclimation, play the leading role in the root. We furthermore critically assessed the roles of key phytohormones, and found abscisic acid (ABA) and ethylene (ET) to be the major regulatory molecules responding to excess NH and activating the MAPK (mitogen-activated protein kinase) signal-transduction pathway. Moreover, we found up-regulated hormone-associated genes are involved in regulating flavonoid biosynthesis and are regulated by tissue flavonoid accumulation.
铵（NH）是包括淹水稻田在内的许多自然和农业生态系统中的主要氮（N）源。虽然水稻被认为是耐铵物种，但在土壤铵浓度升高时仍会遭受铵毒性。铵过量会迅速导致各种生理过程紊乱，最终抑制地上部和根部生长。然而，尚未研究水稻对铵胁迫的全基因组转录反应。在本研究中，我们利用Illumina HiSeqTM 2000通过RNA测序（定量）绘制了铵过量条件下水稻基因表达谱的时空特异性以及根和地上部在不同时间点的基因表达变化。通过比较分析，发现根部在铵暴露4小时和12小时后分别有307个和675个基因上调。在地上部，4小时时有167个基因上调，而12小时时有320个基因上调。根据KEGG分析，上调的差异表达基因主要参与苯丙烷类（如类黄酮）和氨基酸（如脯氨酸、半胱氨酸和蛋氨酸）代谢，据信这通过调节地上部的能量代谢来提高对铵胁迫的耐受性，而引导全株适应的防御和信号通路在根部起主导作用。我们还严格评估了关键植物激素的作用，发现脱落酸（ABA）和乙烯（ET）是响应铵过量并激活丝裂原活化蛋白激酶（MAPK）信号转导途径的主要调节分子。此外，我们发现上调的激素相关基因参与调节类黄酮生物合成，并受组织类黄酮积累的调控。
