title: A single amino acid converts a repressor to an activator of flowering.
abstract: Homologous proteins occurring through gene duplication may give rise to novel functions through mutations affecting protein sequence or expression. Comparison of such homologues allows insight into how morphological traits evolve. However, it is often unclear which changes are key to determining new functions. To address these ideas, we have studied a system where two homologues have evolved clear and opposite functions in controlling a major developmental switch. In plants, flowering is a major developmental transition that is critical to reproductive success. Arabidopsis phosphatidylethanolamine-binding protein homologues TERMINAL FLOWER 1 (TFL1) and FLOWERING LOCUS T (FT) are key controllers of flowering, determining when and where flowers are made, but as opposing functions: TFL1 is a repressor, FT is an activator. We have uncovered a striking molecular basis for how these homologous proteins have diverged. Although <60% identical, we have shown that swapping a single amino acid is sufficient to convert TFL1 to FT function and vice versa. Therefore, these key residues may have strongly contributed to the selection of these important functions over plant evolution. Further, our results suggest that TFL1 and FT are highly conserved in biochemical function and that they act as repressors or activators of flowering through discrimination of structurally related interactors by a single residue.
authors.affiliation: Cell and Developmental Biology, John Innes Centre, Norwich NR4 7UH, UK.
authors.forename: Yoshie
authors.initials: Y
authors.lastname: Hanzawa
authors.forename: Tracy
authors.initials: T
authors.lastname: Money
authors.forename: Desmond
authors.initials: D
authors.lastname: Bradley
mesh_terms: D000595:Amino Acid Sequence; D019943:Amino Acid Substitution / Q000235:genetics; D017360:Arabidopsis / Q000235:genetics* / Q000502:physiology; D029681:Arabidopsis Proteins / Q000737:chemistry / Q000235:genetics* / Q000502:physiology; D019143:Evolution, Molecular; D020131:Genes, Duplicate / Q000235:genetics*; D008958:Models, Molecular; D008969:Molecular Sequence Data; D010641:Phenotype; D010802:Phylogeny; D030821:Plants, Genetically Modified; D010957:Plasmids / Q000235:genetics; D011487:Protein Conformation; D012098:Reproduction / Q000235:genetics / Q000502:physiology; D016415:Sequence Alignment
chemical_list: D029681:Arabidopsis Proteins; C418905:FT protein, Arabidopsis; C102864:TFL1 protein, Arabidopsis