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Abstract:
Phosphatidylethanolamine binding protein (PEBP) is a ubiquitous protein family showing distinctive functionality, among which, flowering locus t (ft) and terminal flower 1 (tfl1) are two representatives of the plantae. though sharing the same origin and structural topology, FT and TFL1 are opposite in function, in which FT promotes while TFL1 inhibits flowering. By means of exonic swapping, a BC surface encoded by two interim segments of their exon four sitting close to the previously identified anion binding pocket was found to be critical to their respective promoting and repressing ability, but the residues involved and their exact way of interaction still remain a mystery. To better understand the machinery underlying plant PEBPs and to figure out by how, the interplay of this antagonistic pair can trigger the plant reproductive switch, as a pilot, we adopted random mutagenesis to introduce point mutation into the FT sequence. then by overexpressing and assessing the functional retainment of around 36000 mutated versions of fts under the Arabidopsis thaliana background, here we report a successful identification of 20 sets of critical amino acid changes that exert a profound impact on the floral promoting ability of FT, among which, 13 sets of these overexpressors can reproducibly show the late flowering phenotype and growth indeterminacy, those are typical to that of TFL1, but not to FT. Further, as more than 80% of these mutations involved a significant while consistent change in side chain properties, linkage has implied and this maybe the first clue on showing by how, this orthologous pair of plant PEBPs be determined and functions as either a floral promoter or repressor, by which modulating such critical time of switch.
