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Iron (Fe) and copper (Cu) are essential micronutrients for plants and humans who consume plants. Their functions are tightly linked. For example, both of Fe and Cu work as cofactors in superoxide dismutase proteins to prevent reactive oxygen species damage. When Fe is removed from nutrient solution, plants uptake more Cu, but how plants sense and respond to Fe status is not fully understood. This thesis includes two projects that focus on Fe and Cu interaction, homeostasis and cross-talk in Arabidopsis thaliana.
Two Arabidopsis ecotypes, Kas-1 and Tsu-1, have difference in timing of Cu accumulation in rosettes under Fe deficiency. In the first study, we utilized a Kas-1 and Tsu-1 recombinant inbred line population form QTL mapping. Based on QTL composite interval mapping, one significant QTL was identified on the chromosome one [C1_23318972, C1_25175851] which explained 10% of the variation. We identified candidate genes based on their functions and amino acids differences between Kas-1 and Tsu-1. A time course experiment suggested that two candidate genes, HMA5 and ATX1, can’t account for differences between Kas-1 and Tsu-1 for timing of Cu accumulation.
Genome-wide transcriptional profiling with Illumina HiSeq technology was used to reveal Fe/Cu cross-talk gene lists. The use of SQUAMOSA Promoter Binding Protein-Like7 (SPL7) mutant plants in Fe and Cu deficiencies addressed the research hypothesis that the uptake of Cu under Fe deficiency is independent of the normal Cu uptake system, and we identified specific SPL7 regulated genes under Cu deficiency. Wild-type Col-0 and mutant spl7 showed different patterns of classic bHLH family genes bHLH38, bHLH39, bHLH100, and bHLH101. Several ETHYLENE RESPONSIVE ELEMENT BINDING FACTORS (ERFs) were downregulated in Col-0, not in spl7. The wild type Col-0 and spl7 mutant transcriptional profiling would give significant insight into Fe and Cu homeostasis.
Advisor: Brian Waters