Figure 1.

Analysis of FER‐LIKE IRON DEFICIENCY‐INDUCED TRANSCRIPTION FACTOR (FIT) protein sequence reveals novel putative phosphorylation target sites in FIT‐C. (a) Phosphorylation site prediction of FIT. Full‐length amino acid sequence of FIT (top), composed of an amino‐terminal (N‐term), basic helix–loop–helix (bHLH; gray), and carboxyl‐terminal (C‐term) region, also known as FIT‐C, divided by red bars. In silico prediction by netphos2.0 identified potential phosphorylation sites (bottom, bold), of which six are located in FIT‐C (bold, colored). Colors reflect the confidence score of the prediction. (b) Multiple sequence alignment, showing the FIT‐C region with putative phosphorylation sites, compared with orthologues in angiosperms. AtFIT is presented in bold, conserved putative phosphorylation sites are bold and underlined, and these sites are highlighted for comparison in gray. B.A., basal angiosperms, M., monocots, E., eudicots. (c) Sequence alignment of subgroup IIIa bHLH proteins, showing the FIT‐C region with putative phosphorylation sites. AtFIT full‐length protein sequence was aligned with bHLH proteins AT2G16910 and AT4G21330 (subgroup IIIa). FIT target sites are not conserved between the bHLH proteins. (d) Identification of phosphorylation motifs and phospho‐mutants of FIT‐C. Predicted phosphorylated amino acids are presented in bold, underlined; known phosphorylation motifs are highlighted in yellow. FIT target site phospho‐mutants are shown in gray boxes, with phospho‐dead (serine to alanine/S to A, tyrosine to phenylalanine/Y to F) and phospho‐mimicking (S, Y to glutamate/S, Y to E) FIT forms.