Maize Interveinal Chlorosis 1 Links the Yang Cycle and Fe Homeostasis through Nicotianamine Biosynthesis.
Maize Interveinal Chlorosis 1 Links the Yang Cycle and Fe Homeostasis through Nicotianamine Biosynthesis.
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玉米脉间失绿 1 通过烟酰胺生物合成将阳循环和铁稳态联系起来。
DOI：
10.1093/plphys/kiac009
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发表时间：
2022-01
期刊：
影响因子：
7.4
通讯作者：
Chen Shaojiang
中科院分区：
文献类型：
--
作者：
Sun Wentao;Zhou Xiaojin;Chen Chen;Zhang Xin;Tian Xiaolong;Xiao Ke;Liu Chenxu;Chen Rumei;Chen Shaojiang
阳离子循环参与植物生长发育的许多重要代谢途径。作为阳循环的延伸产物，乙烯和多胺的功能和调控网络得到了很好的表征。烟胺(NA)也是这一循环的产物，是植物体内铁稳态的关键金属螯合剂。然而，阳离子循环和NA生物合成之间的相互作用仍不清楚。在此，我们克隆了玉米脉间失绿症1(MIC1)基因，该基因编码5‘-甲硫基腺苷核苷酶(MTN)，在玉米(Zea Mays)的5’-甲基硫代腺苷(MTA)回收和NA生物合成中起重要作用。MIC1基因第4外显子的单个碱基G-A转换导致Gly向Asp的转变，导致MTA增加，铁分布减少，幼苗生长迟缓。CRISPR/Cas9敲除ZmMIC1而不是其类似物ZmMTN2会导致玉米叶脉间失绿，表明ZmMIC1是玉米MTN活性的主要调控基因。转录组分析显示为典型的缺铁反应。然而，代谢分析显示，MIC1中的NA含量显著减少，这表明该突变体的NA生物合成受到了损害。外源NA处理可暂时逆转MIC1苗脉间失绿表型。此外，高表达NA合成酶基因的MIC1突变体不仅从脉间失绿和生长迟缓中恢复，而且还具有可育性。这些发现提供了阳离子循环和NA生物合成之间的联系，这突出了玉米中铁的动态平衡调节的一个方面。
The Yang cycle is involved in many essential metabolic pathways in plant growth and development. As extended products of the Yang cycle, the function and regulation network of ethylene and polyamines are well characterized. Nicotianamine (NA) is also a product of this cycle and works as a key metal chelator for Fe homeostasis in plants. However, interactions between the Yang cycle and NA biosynthesis remain unclear. Here, we cloned maize interveinal chlorosis 1 (mic1), encoding a 5'-methylthioadenosine nucleosidase (MTN), that is essential for 5'-methylthioadenosine (MTA) salvage and NA biosynthesis in maize (Zea mays). A single base G-A transition in the 4th exon of mic1 causes a Gly to Asp change, resulting in increased MTA, reduced iron distribution, and growth retardation of seedlings. Knockout of ZmMIC1 but not its paralogue ZmMTN2 by CRISPR/Cas9 causes interveinal chlorosis, indicating ZmMIC1 is mainly responsible for MTN activity in maize. Transcriptome analysis showed a typical response of iron deficiency. However, metabolic analysis revealed dramatically reduced NA content in mic1, suggesting NA biosynthesis was impaired in the mutant. Exogenous application of NA transiently reversed the interveinal chlorosis phenotype of mic1 seedlings. Moreover, the mic1 mutant overexpressing a NA synthase gene not only recovered from interveinal chlorosis and growth retardation but was also fertile. These findings provide a link between the Yang cycle and NA biosynthesis, which highlights an aspect of Fe homeostasis regulation in maize.