Functional analysis of orthologous transcription factors FLOWERING LOCUS C and PERPETUAL FLOWERING 1 in A. thaliana and A. alpina

The orthologous transcription factors PEP1 and FLC repress flowering before vernalization in perennial A. alpina and annual A. thaliana, respectively. In A. alpina, PEP1 also represses flowering after vernalization to ensure vegetative growth after flowering, a crucial step in the perennial life-cycle. Genome-wide comparison of PEP1 and FLC targets showed high divergence. Conserved target genes were mainly associated with the control of flowering time and flower development, the main function of PEP1 and FLC. Species-specific target genes in both species were associated with responses to environmental stimuli and hormones like gibberellins. Phenotypic analysis revealed that the pep1 mutant displays several phenotypes that resemble a gibberellin-treated plant, suggesting that PEP1 affects the gibberellin response. We found that gibberellins promote floral induction during vernalization, however gibberellin levels were not increased during vernalization in wild-type or pep1. Before vernalization, pep1 had increased levels of gibberellins that might cause phenotypic changes in the mutant. In addition, we found that PEP1 represses gibberellin signaling which might also contribute to phenotypic changes in pep1 and is likely to delay floral induction in early stages of vernalization. Thus, PEP1 links environmental and developmental responses within the perennial life cycle of A. alpina by modifying the gibberellins response.