Mediator subunit 16 functions in the regulation of iron uptake gene expression in Arabidopsis.
Mediator subunit 16 functions in the regulation of iron uptake gene expression in Arabidopsis.
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DOI：
10.1111/nph.12860
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发表时间：
2014-08
期刊：
影响因子：
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通讯作者：
Yu’e Zhang;Huilan Wu;Ning Wang;Huajie Fan;Chunlin Chen;Yan Cui;Hongfei Liu;H. Ling
中科院分区：
文献类型：
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作者：
Yu’e Zhang;Huilan Wu;Ning Wang;Huajie Fan;Chunlin Chen;Yan Cui;Hongfei Liu;H. Ling
铁是植物生长发育的必需营养素，其吸收受到严格控制。在铁限制下，FIT与四种Ib bHLH蛋白二聚化并激活铁摄取基因的表达。然而，二聚复合物如何激活下游基因仍不清楚。利用正向遗传学方法，筛选出一株低铁敏感突变株。通过基因表达、蛋白质亚细胞定位、蛋白质-蛋白质相互作用和染色质免疫沉淀等方法，研究了MED 16在铁稳态中的生物学功能。MED 16的损伤显著降低拟南芥根中FRO 2和IRT 1的表达。MED 16突变体在铁限制条件下表现出较低的地上部铁浓度和严重的叶片失绿，而在铁充足条件下则与野生型一样正常生长。此外，我们发现MED 16与FIT相互作用，并在缺铁条件下改善FIT/Ib bHLH复合物与FRO 2和IRT 1启动子的结合。此外，我们发现许多由FIT调控的缺铁反应基因也受到MED 16的控制。因此，MED 16参与了缺铁反应，并在铁限制下调节铁摄取基因的表达。我们的研究结果增加了对植物铁吸收和体内平衡的分子调控机制的理解。
Iron is an essential nutrient for plant growth and development, and its absorption is tightly controlled. Under iron limitation, FIT dimerizes with the four Ib bHLH proteins and activates the expression of iron uptake genes. However, how the dimerized complex activates downstream genes remains unclear. Using forward genetics, a low-iron-sensitive mutant was screened. The corresponding gene (MED16) was isolated, and its biological functions in iron homeostasis were characterized using approaches such as gene expression, protein subcellular localization, protein-protein interaction and chromatin immunoprecipitation assay. Lesion of MED16 significantly reduced FRO2 and IRT1 expression in Arabidopsis roots. The MED16 mutants showed a low shoot iron concentration and severe leaf chlorosis under iron limitation, whereas it grew normally as wild-type under iron sufficiency. Furthermore, we showed that MED16 interacted with FIT and improved the binding of the FIT/Ib bHLH complex to FRO2 and IRT1 promoters under iron-deficient conditions. Additionally, we found that many iron-deficient response genes, which are regulated by FIT, were also controlled by MED16. In conclusion, MED16 is involved in the iron deficiency response, and modulates the iron uptake gene expression under iron limitation. Our results increase the understanding of the molecular regulation mechanisms underlying iron uptake and homeostasis in plants.