title: Mediator subunit 16 functions in the regulation of iron uptake gene expression in Arabidopsis.
abstract: 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.
authors.affiliation: The State Key Laboratory of Plant Cell and Chromosome Engineering, Institute of Genetics and Developmental Biology, Chinese Academy of Sciences, No. 1 West Beichen Road, Chaoyang District, Beijing, 100101, China.
authors.forename: Yue
authors.initials: Y
authors.lastname: Zhang
authors.forename: Huilan
authors.initials: H
authors.lastname: Wu
authors.forename: Ning
authors.initials: N
authors.lastname: Wang
authors.forename: Huajie
authors.initials: H
authors.lastname: Fan
authors.forename: Chunlin
authors.initials: C
authors.lastname: Chen
authors.forename: Yan
authors.initials: Y
authors.lastname: Cui
authors.forename: Hongfei
authors.initials: H
authors.lastname: Liu
authors.forename: Hong-Qing
authors.initials: HQ
authors.lastname: Ling
mesh_terms: D000483:Alleles; D017360:Arabidopsis / Q000187:drug effects / Q000235:genetics* / Q000378:metabolism; D029681:Arabidopsis Proteins / Q000235:genetics / Q000378:metabolism*; D005453:Fluorescence; D020869:Gene Expression Profiling; D018506:Gene Expression Regulation, Plant / Q000187:drug effects; D017343:Genes, Plant; D005966:Glucuronidase / Q000378:metabolism; D007501:Iron / Q000378:metabolism* / Q000494:pharmacology; D009154:Mutation / Q000235:genetics; D010641:Phenotype; D018517:Plant Roots / Q000187:drug effects / Q000235:genetics; D018520:Plant Shoots / Q000187:drug effects / Q000378:metabolism; D011401:Promoter Regions, Genetic; D011485:Protein Binding / Q000187:drug effects / Q000235:genetics; D021122:Protein Subunits / Q000235:genetics / Q000378:metabolism*; D021381:Protein Transport / Q000187:drug effects; D013347:Subcellular Fractions / Q000187:drug effects / Q000378:metabolism; D015534:Trans-Activators / Q000235:genetics / Q000378:metabolism*
chemical_list: D029681:Arabidopsis Proteins; D021122:Protein Subunits; C575423:SFR6 protein, Arabidopsis; D015534:Trans-Activators; D007501:Iron; D005966:Glucuronidase
keywords: Arabidopsis; Mediator subunit 16; iron homeostasis; low-iron-sensitive mutant; regulation of iron uptake gene expression