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Abstract
背景回顾：Plants generally enhance their root growth in the form of greater biomass and/or root length to boost nutrient uptake in response to short-term low nitrogen (LN).
提出问题：However, the underlying mechanisms of short-term LN-mediated root growth remain largely elusive.
主要发现：Our genome-wide association study, haplotype analysis, and phenotyping of transgenic plants showed that the crucial nitrate signaling component NIN-LIKE PROTEIN3.2 (ZmNLP3.2), a positive regulator of root biomass, is associated with natural variations in root biomass of maize (Zea mays L.) seedlings under LN.
结果1-ZmNLP3.2负调控ZmAUX/IAA4：The monocot-specific gene AUXIN/INDOLE-3-ACETIC ACID14 (ZmAux/IAA14) exhibited opposite expression patterns to ZmNLP3.2 in ZmNLP3.2 knockout and overexpression lines, suggesting that ZmNLP3.2 hampers ZmAux/IAA14 transcription.
结果2-ZmAUX/IAA4作用于低氮下的根生长：Importantly, ZmAux/IAA14 knockout seedlings showed a greater root dry weight (RDW), whereas ZmAux/IAA14 overexpression reduced RDW under LN compared with wild-type plants, indicating that ZmAux/IAA14 negatively regulates the RDW of LN-grown seedlings.
结果3-ZmNLP3.2-ZmARF19-ZmAUX/IAA4：Moreover, in vitro and vivo assays indicated that AUXIN RESPONSE FACTOR19 (ZmARF19) binds to and transcriptionally activates ZmAux/IAA14, which was weakened by the ZmNLP3.2–ZmARF19 interaction. The zmnlp3.2 ZmAux/IAA14-OE seedlings exhibited further reduced RDW compared to ZmAux/IAA14 overexpression lines when subjected to LN treatment, corroborating the ZmNLP3.2–ZmAux/IAA14 interaction.
结论：Thus, our study reveals a ZmNLP3.2–ZmARF19–ZmAux/IAA14 module regulating root biomass in response to nitrogen limitation in maize.
摘 要
植物在响应短期的低氮胁迫时，一般能够通过增强生物量或者根系生长来获取更多的营养。但是，短期低氮胁迫介导的根生长调控机制仍不清楚。作者通过GWAS分析、单倍型拆分以及转基因植株的表型分型，揭示了氮信号转导核心组分ZmNLP3.2作为根生物量的正调控因子，与玉米实生苗在低氮条件下的根生物量自然变异有关。在ZmNLP3.2敲除和过表达株系中，单子叶植物特有基因ZmAux/IAA14存在与ZmNLP3.2基因完全相反的表达模式，表明ZmNLP3.2阻碍了ZmAux/IAA14的转录。重要的是，相比于野生型植株，低氮条件下ZmAux/IAA14敲除植株的根干重更高，而ZmAux/IAA14过表达植株的根干重更低，表明ZmAux/IAA14负调控低氮条件下的根干重。此外，体内和体外试验显示ZmARF19能够结合并转录激活ZmAux/IAA14的表达，而这一过程又会被ZmNLP3.2–ZmARF19的互作所削弱。相比于ZmAux/IAA14过表达植株，在ZmAux/IAA14过表达背景下敲除ZmNLP3.2会导致其在低氮条件下的根干重更低，进一步证实了ZmNLP3.2–ZmAux/IAA14的互作。因此，本文的研究揭示了ZmNLP3.2–ZmARF19–ZmAux/IAA14模块作用于玉米低氮条件下的根生物量调控。
中国农业大学李学贤教授为本文通讯作者，王瑞丰博士为本文第一作者。该研究得到了国家重点研发计划（2021YFF1000500）和国家自然科学基金（31972491）的联合资助。
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