A single residue change in the product of the chrysanthemum gene TPL1-2 leads to a failure in its repression of flowering

Abstract The TPL/TPR co-repressor is involved in many plant signaling pathways, including those regulating the switch from vegetative to reproductive growth. Here, a TPL homolog (TPL 1-2 ) was isolated from chrysanthemum. Its product was found to be deposited in the nucleus. The abundance of TPL1-2 transcript varied across the plant, with its highest level being recorded in the stem apex, and its lowest in the root and stem. In the leaf, the abundance of TPL1-2 transcript was highest at dusk in plants exposed to long days, and at dawn in those exposed to short days. Site-directed mutagenesis was used to induce an N176H mutation in TPL1-2. The constitutive expression in Arabidopsis thaliana of the wild type and the mutated alleles of TPL1-2 had a contrasting effect on flowering time, with the mutant transgene expressors flowering later than the wild type transgene expressors. The flowering-related genes FT , TSF , FUL and AP1 were all more strongly transcribed in the mutant transgene expressors than in the wild type transgene expressors.