Expression of Several Genes Involved in the Fe Homeostasis Transcriptional Regulatory Network Is Compromised in the bhlh121 Loss-of-Function Mutants.
(A) Relative expression of FIT, bHLH38, PYE, BTS, BTSL1, IMA1, IMA2, and IMA3. Relative expression was determined by RT-qPCR in 1-week-old Arabidopsis seedlings grown on Fe-sufficient or Fe-deficient medium. Means within each condition with the same letter are not significantly different according to one-way ANOVA followed by post hoc Tukey test, P < 0.05 (n = 3 technical repeats from one representative experiment). Error bars show ±sd. Each experiment (biological repeat) comprised pooled RNA extracted from ∼30 seedlings and was independently repeated three times.
(B) ChIP-qPCR analysis of the binding of bHLH121 to the promoters of FIT, bHLH38, bHLH39, bHLH100, bHLH101, PYE, BTS, BTSL1, IMA1, IMA2, IMA3, F6’H1, S8H, CYP82C4, MYB10, and MYB72. Chromatin from the two complemented bhlh121-2 lines expressing the ProbHLH121:gbHLH121:GFP construct subjected to Fe deficiency was extracted using anti-GFP antibodies. Seedlings expressing GFP under the control of the ILR3 promoter (ProILR3:GFP) were used as a negative control. qPCR was used to quantify enrichment of bHLH121 on the selected gene promoters. Means within each condition with the same letter are not significantly different according to one-way ANOVA followed by post hoc Tukey test, P < 0.05 (n = 4 to 6 technical repeats from one representative experiment). Error bars show ±sd. Each experiment (biological repeat) comprised pooled chromatin immunoprecipitated from ∼500 seedlings (2 g) and was independently repeated two times.