Requirement and Functional Redundancy of Ib Subgroup bHLH Proteins for Iron Deficiency Responses and Uptake in Arabidopsis thaliana  

作　　者：Ning Wang Yan Cui Yi Liu Huajie Fan Juan Du Zongan Huang Youxi Yuan Huilan Wu Hong-Qing Ling 

机构地区：[1]State Key Laboratory of Plant Cell and Chromosome Engineering, Institute of Genetics and Developmental Biology, Chinese Academy of Sciences, No. 1West Beichen Road, Chaoyang District, Beijing 100101, China [2]Graduate School of theChinese Academy of Sciences, Yuquan Road, Shijingshan District, Beijing 100049, China [3]Present address: Department of Biochemistry and Molecular Biology, Pennsylvania State University, University Park, PA 16802, USA [4]Present address: Institute of Vegetable Crops, Wenzhou Academy of Agricultural Sciences, Wenzhou Vocation College of Science and Technology,Wenzhou, 325014, China

出　　处：《Molecular Plant》2013年第2期503-513,共11页分子植物（英文版）

摘　　要：The Ib subgroup of the bHLH gene family in Arabidopsis contains four members （AtbHLH38, AtbHLH39, AtbHLHIO0, and AtbHLH101）. AtbHLH38 and AtbHLH39 were previously confirmed to interact with FER-like iron deft-ciency induced transcription factor （FIT）, directly functioning in activation of the expression of ferric-chelate reductase FRO2 and high-affinity ferrous iron transporter IRT1. In this work, we characterized the functions of AtbHLH100 and AtbHLH101 in the regulation of the iron-deficiency responses and uptake. Yeast two-hybrid analysis and bimolecular fluorescence complementation assay demonstrated that both AtbHLH100 and AtbHLH101 could interact with FIT. Dual expression of either AtbHLH100 or AtbHLH101 with FIT in yeast cells activated the GUS expression driven by promoters of FRO2 and IRT1. The plants overexpressing FIT together with AtbHLHI01 showed constitutive expression of FRO2 and IRT1 in roots, and accumulated more iron in shoots. Further, the single, double, and triple knockout mutants of AtbHLH38, AtbHLH39, AtbHLH100, and AtbHLH101 were generated and characterized. The FRO2 and IRT1 expression in roots and the iron content in shoots were more drastically decreased in the triple knockout mutant of AtbHLH39, AtbHLH100, and AtbHLH101 than that of the other available double and triple mutants of the four genes. Comparison of the physiological responses as well as the expression of FRO2 and IRT1 in the multiple knockout mutants under iron deficiency revealed that AtbHLH100, AtbHLH38, AtbHLH101, and AtbHLH39 played the gradually increased important role in the iron-deficiency responses and uptake. Taken all together, we conclude that the four Ib subgroup bHLH proteins are required and possess redundant functions with differential significance for activation of iron-deficiency responses and uptake in Arabidopsis.The Ib subgroup of the bHLH gene family in Arabidopsis contains four members （AtbHLH38, AtbHLH39, AtbHLHIO0, and AtbHLH101）. AtbHLH38 and AtbHLH39 were previously confirmed to interact with FER-like iron deft-ciency induced transcription factor （FIT）, directly functioning in activation of the expression of ferric-chelate reductase FRO2 and high-affinity ferrous iron transporter IRT1. In this work, we characterized the functions of AtbHLH100 and AtbHLH101 in the regulation of the iron-deficiency responses and uptake. Yeast two-hybrid analysis and bimolecular fluorescence complementation assay demonstrated that both AtbHLH100 and AtbHLH101 could interact with FIT. Dual expression of either AtbHLH100 or AtbHLH101 with FIT in yeast cells activated the GUS expression driven by promoters of FRO2 and IRT1. The plants overexpressing FIT together with AtbHLHI01 showed constitutive expression of FRO2 and IRT1 in roots, and accumulated more iron in shoots. Further, the single, double, and triple knockout mutants of AtbHLH38, AtbHLH39, AtbHLH100, and AtbHLH101 were generated and characterized. The FRO2 and IRT1 expression in roots and the iron content in shoots were more drastically decreased in the triple knockout mutant of AtbHLH39, AtbHLH100, and AtbHLH101 than that of the other available double and triple mutants of the four genes. Comparison of the physiological responses as well as the expression of FRO2 and IRT1 in the multiple knockout mutants under iron deficiency revealed that AtbHLH100, AtbHLH38, AtbHLH101, and AtbHLH39 played the gradually increased important role in the iron-deficiency responses and uptake. Taken all together, we conclude that the four Ib subgroup bHLH proteins are required and possess redundant functions with differential significance for activation of iron-deficiency responses and uptake in Arabidopsis.

关 键 词：transcription factor bHLH protein iron homeostasis FIT. 

分 类 号：Q943[生物学—植物学] TP333[自动化与计算机技术—计算机系统结构]