Classic regulators, new functions: FT and TFL1 shape Arabidopsis seed traits

FLOWERING LOCUS T (FT) and TERMINAL FLOWER1 (TFL1), two members of the phosphatidylethanolamine-binding protein (PEBP) family, are well-known regulators of flowering time and inflorescence architecture in Arabidopsis thaliana. However, recent work by Bigas et al. uncovers their additional roles in regulating seed traits, such as dormancy and size. Using CRISPR/Cas9-generated mutants in the Ler background, the study shows that tfl1 mutants produce larger seeds with reduced dormancy, while ft mutants exhibit increased dormancy with minimal changes in seed size. Reporter assays reveal that both proteins co-localize in maternal vascular tissues, but only TFL1 is present in the endosperm, suggesting tissue-specific roles. TFL1, but not FT, influences seed size, potentially by delaying endosperm cellularization. The authors propose two hypotheses: one in which FT and TFL1 act together in a shared pathway affecting proanthocyanidin biosynthesis in maternal tissues, and another in which they function independently due to their distinct expression patterns. These findings expand the known functions of FT and TFL1, emphasizing the importance of revisiting classic developmental regulators in the context of non-canonical traits, with broad implications for crop improvement and agricultural productivity. (Summary by Gourav Arora @gourav_arora_g)  J. Exp. Bot 10.1093/jxb/erae466