The essential basic helix-loop-helix protein FIT1 is required for the iron deficiency response.
Regulation of iron uptake is critical for plant survival. Although the activities responsible for reduction and transport of iron at the plant root surface have been described, the genes controlling these activities are largely unknown. We report the identification of the essential gene Fe-deficiency Induced Transcription Factor 1 (FIT1), which encodes a putative transcription factor that regulates iron uptake responses in Arabidopsis thaliana. Like the Fe(III) chelate reductase FRO2 and high affinity Fe(II) transporter IRT1, FIT1 mRNA is detected in the outer cell layers of the root and accumulates in response to iron deficiency. fit1 mutant plants are chlorotic and die as seedlings but can be rescued by the addition of supplemental iron, pointing to a defect in iron uptake. fit1 mutant plants accumulate less iron than wild-type plants in root and shoot tissues. Microarray analysis shows that expression of many (72 of 179) iron-regulated genes is dependent on FIT1. We demonstrate that FIT1 regulates FRO2 at the level of mRNA accumulation and IRT1 at the level of protein accumulation. We propose a new model for iron uptake in Arabidopsis where FRO2 and IRT1 are differentially regulated by FIT1.
Colangelo
Elizabeth P
EP
Department of Biological Sciences, Dartmouth College, Hanover, New Hampshire 03755, USA.
Guerinot
Mary Lou
ML
D017360:Arabidopsis / Q000235:genetics / Q000378:metabolism*; D029681:Arabidopsis Proteins / Q000235:genetics / Q000302:isolation & purification / Q000378:metabolism*; D051792:Basic Helix-Loop-Helix Proteins; D001665:Binding Sites / Q000235:genetics; D027682:Cation Transport Proteins / Q000235:genetics / Q000378:metabolism; D017124:Conserved Sequence / Q000235:genetics; D038181:FMN Reductase / Q000235:genetics / Q000378:metabolism; D018506:Gene Expression Regulation, Plant / Q000235:genetics; D005809:Genes, Regulator / Q000235:genetics; D018257:Helix-Loop-Helix Motifs / Q000235:genetics*; D007501:Iron / Q000378:metabolism; D000090463:Iron Deficiencies; D009154:Mutation / Q000235:genetics; D020411:Oligonucleotide Array Sequence Analysis; D018517:Plant Roots / Q000235:genetics / Q000378:metabolism*; D030821:Plants, Genetically Modified / Q000235:genetics / Q000378:metabolism; D011401:Promoter Regions, Genetic / Q000235:genetics; D012333:RNA, Messenger / Q000378:metabolism; D036226:Seedlings / Q000235:genetics / Q000378:metabolism; D017386:Sequence Homology, Amino Acid; D014157:Transcription Factors / Q000235:genetics / Q000302:isolation & purification / Q000378:metabolism*
D029681:Arabidopsis Proteins; D051792:Basic Helix-Loop-Helix Proteins; D027682:Cation Transport Proteins; D038181:FMN Reductase; D007501:Iron; D012333:RNA, Messenger; D014157:Transcription Factors; C501411:FIT1 protein, Arabidopsis; C099651:IRT1 protein, Arabidopsis; C023903:ferric citrate iron reductase