Gong Xiaoping, Liu Xiaoyang, Pan Qingchun, Mi Guohua, Chen Fanjun, Yuan Lixing
College of Resources and Environmental Sciences; National Academy of Agriculture Green Development, Key Laboratory of Plant-Soil Interactions of MOE, China Agricultural University, Beijing, China.
Center for Crop Functional Genomics and Molecular Breeding, China Agricultural University, Beijing, China.
J Exp Bot. 2020 Aug 6;71(16):5061-5073. doi: 10.1093/jxb/eraa229.
In plants, nitrogen remobilization from source to sink organs is an important process regulated by complex transcriptional regulatory networks. However, the relationship between nitrogen remobilization and leaf senescence and the molecular regulatory network that controls them are unknown in maize. Here, using 15N labeling and a transcriptome approach, a dynamic analysis of the nitrogen remobilization process was conducted in two elite maize inbred lines (PH4CV and PH6WC) with contrasting leaf senescence. PH4CV showed higher nitrogen remobilization efficiency (NRE) than PH6WC, mainly in the middle and lower leaves from 15 d to 35 d after silking. The co-expression network analysis revealed that ethylene and cytokinin metabolism-related genes triggered the onset of nitrogen remobilization, while abscisic acid and jasmonic acid biosynthesis-related genes controlled the progression of nitrogen remobilization. By integrating genetic analysis, functional annotation, and gene expression, two candidate genes underlying a major quantitative trait locus of NRE were identified, namely an early senescence acting gene (ZmASR6) and an ATP-dependent Clp protease gene (GRMZM2G172230). Hormone-coupled transcription factors and downstream target genes reveal a gene regulatory network for the nitrogen remobilization process after silking in maize. These results uncovered a sophisticated regulatory mechanism for nitrogen remobilization, and further provided characterization of valuable genes for genetic improvement of nitrogen use efficiency in maize.
在植物中，氮从源器官向库器官的再分配是一个受复杂转录调控网络调节的重要过程。然而，在玉米中，氮再分配与叶片衰老之间的关系以及控制它们的分子调控网络尚不清楚。在此，利用15N标记和转录组方法，对两个叶片衰老特性不同的优良玉米自交系（PH4CV和PH6WC）的氮再分配过程进行了动态分析。PH4CV的氮再分配效率（NRE）高于PH6WC，主要体现在吐丝后15天至35天的中下部叶片。共表达网络分析表明，乙烯和细胞分裂素代谢相关基因触发了氮再分配的起始，而脱落酸和茉莉酸生物合成相关基因控制了氮再分配的进程。通过整合遗传分析、功能注释和基因表达，鉴定出了两个位于氮再分配效率主要数量性状位点的候选基因，即一个早衰作用基因（ZmASR6）和一个ATP依赖的Clp蛋白酶基因（GRMZM2G172230）。激素偶联转录因子和下游靶基因揭示了玉米吐丝后氮再分配过程的基因调控网络。这些结果揭示了氮再分配的复杂调控机制，并进一步为玉米氮利用效率的遗传改良提供了有价值基因的特征。
