Department of Plant Sciences

Arabidopsis was used as a model plant to study the molecular regulation mechanism of iron uptake in strategy I plants and two new iron-regulated bHLH proteins (AtbHLH38 and AtbHLH39) have been identified. They showed interaction with FIT, a central regulatory gene involved in regulation iron uptake in Arabidopsis, by yeast-two-hybridization. Expression of FIT/AtbHLH38 or FIT/AtbHLH39 in yeast cells was able to activate GUS expression driven by AtFRO2 (ferric chelate reductase) and AtIRT1 (ferrous transporter) promoters. Overexpression of both FIT and either AtbHLH38 or AtbHLH39 converted the expression of the iron uptake genes AtFRO2 and AtIRT1 from induced to constitutively, and the overexpression plants accumulated more iron in their shoots than the wild type and exhibited more tolerance against iron deficiency. The results indicate that transcription of the iron uptake genes AtFRO2 and AtIRT1 in Arabidopsis is directly regulated by a complex of FIT/AtbHLH38 or FIT/AtbHLH39.