Investigations of iron-regulated genes in Arabidopsis thaliana [abstract]
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Iron is essential for virtually all life, but little is known about the way plants sense, take up, and maintain iron. In an effort to learn more about how plants use this vital nutrient, two projects using the model plant Arabidopsis thaliana were undertaken. The first was a novel genetic screen using transgenic plants harboring the reporter Green Fluorescent Protein (GFP) driven by the iron-regulated AtFer1 promoter. One mutant, OAF 102, was identified for its constitutively high GFP fluorescence relative to unmutagenized transgenic controls. OAF 102 has constitutively elevated GFP mRNA but retains iron-dependent expression of AtFer1; all other iron-related traits tested were similar in OAF 102 and the transgenic parent. Sequencing of the transgenic promoter from OAF 102 did not reveal any mutations in the TATA box, G Box, or iron-dependent regulatory sequence (IDRS). The decoupled regulation of these genes may indicate an epigenetic mutation or a mutation elsewhere in the genome. The other project is an investigation of mutant lines singly and doubly mutant for T-DNA insertions in four bHLH transcription factors found to be upregulated during iron deficiency. Neither single nor double mutant lines showed alterations in ferric-chelate reductase activity. This may reflect a role in iron homeostasis that is not detectable using this tool or a degree of functional redundancy. Further investigation of these T-DNA lines and of OAF 102 is ongoing.