Minisymposium 6: Intercellular Signaling
Abs #
16003: Arabidopsis TFL1 has signal peptide for intercellular trafficking
Arabidopsis TERMINAL FLOWER 1 (TFL1) gene is required for the establishment and maintenance of inflorescence meristem (IM), since tfl1 mutants show early flowering and terminal flower phenotype. Using GFP-TFL1 fusion protein, we have shown that TFL1 protein moves from inner region of L3 layer, where the TFL1 transcript is accumulated, to outer layers of shoot apical meristem (SAM) in accordance with the vegetative to reproductive phase transition. That is TFL1 protein does not move in the vegetative meristem (VM), but start to move when the SAM is switched to IM by floral induction and in the mature IM, TFL1 protein becomes to localize in the whole region of the SAM. This protein movement also occurs from L1 to L3 direction but which is tissue specific since TFL1 does not move in the flower stalk. Protein movement is essential for TFL1 function since immobilised TFL1 protein does not complement tfl1 mutant phenotype.
Molecular dissection of TFL1 protein revealed that 20 amino acids region is sufficient for TFL1 protein trafficking. This region is highly conserved among TFL1/FT family proteins. GFP coupled this peptide shows the same manner of protein movement as TFL1 and TFL1 protein does not move when this region was removed or substituted. A mutant TFL1 protein which has single amino acid substitution in this region, was prevented from protein trafficking and did not rescue tfl1 mutation when expressed by either genomic context or CaMV 35S promoter. This result suggests that protein movement and TFL1 function are correlated with each other. We are now making a series of mutant proteins to reveal whether the TFL1 function and its protein trafficking can be separated or not. The essential peptide sequence required for TFL1/FT family protein movement will be presented.
