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Factorial combinations of protein interactions generate a multiplicity of florigen activation complexes in wheat and barley
Author(s) -
Li Chengxia,
Lin Huiqiong,
Dubcovsky Jorge
Publication year - 2015
Publication title -
the plant journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 3.058
H-Index - 269
eISSN - 1365-313X
pISSN - 0960-7412
DOI - 10.1111/tpj.12960
Subject(s) - bimolecular fluorescence complementation , meristem , gene , cytoplasm , biology , complementation , transcription (linguistics) , locus (genetics) , dna , microbiology and biotechnology , protein–protein interaction , biochemistry , genetics , mutant , linguistics , philosophy
Summary The FLOWERING LOCUS T ( FT ) protein is a central component of a mobile flowering signal (florigen) that is transported from leaves to the shoot apical meristem ( SAM ). Two FT monomers and two DNA ‐binding bZIP transcription factors interact with a dimeric 14‐3‐3 protein bridge to form a hexameric protein complex. This complex, designated as the ‘florigen activation complex’ ( FAC ), plays a critical role in flowering. The wheat homologue of FT , designated FT 1 (= VRN 3), activates expression of VRN 1 in the leaves and the SAM , promoting flowering under inductive long days. In this study, we show that FT 1, other FT ‐like proteins, and different FD ‐like proteins, can interact with multiple wheat and barley 14‐3‐3 proteins. We also identify the critical amino acid residues in FT 1 and FD ‐like proteins required for their interactions, and demonstrate that 14‐3‐3 proteins are necessary bridges to mediate the FT 1–Ta FDL 2 interaction. Using in vivo bimolecular fluorescent complementation (Bi FC ) assays, we demonstrate that the interaction between FT 1 and 14‐3‐3 occurs in the cytoplasm, and that this complex is then translocated to the nucleus, where it interacts with Ta FDL 2 to form a FAC . We also demonstrate that a FAC including FT 1, Ta FDL 2 and Ta14‐3‐3C can bind to the VRN 1 promoter in vitro . Finally, we show that relative transcript levels of FD ‐like and 14‐3‐3 genes vary among tissues and developmental stages. Since FD ‐like proteins determine the DNA specificity of the FAC s, variation in FD ‐like gene expression can result in spatial and temporal modulation of the effects of mobile FT ‐like signals.