TFL1 homolog integrates temperature signals to control timing of developmental transitions in woodland strawberry

Abstract

In overwintering plants of temperate climates, inflorescence and flower buds commonly form in autumn under cool temperatures, while flowering occurs the following spring. However, how cool temperatures regulate inflorescence and flower development remains poorly understood. We used woodland strawberry (Fragaria vesca L.), a perennial Rosaceae herb, to investigate the effects of cool temperature on reproductive development. We characterized temperature-dependent developmental patterns at macroscopic and microscopic scale and combined time- and stage-specific gene expression analyses. We show that cool temperature accelerates floral transition but subsequently slows inflorescence and flower development, causing increased inflorescence branching, higher floral organ numbers, and berry fasciation. These effects were restricted to the apical inflorescence and flower meristems, whereas higher-order meristems remained unaffected. Expression analyses revealed stage- and temperature-dependent changes in the abundance and spatial distribution of TERMINAL FLOWER1 (FvTFL1) encoding the floral repressor. Loss of functional FvTFL1 abolished temperature-dependent differences in floral transition, inflorescence branching, and floral organ numbers. Our results establish FvTFL1 as a major regulator of temperature-responsive reproductive development. The stage-specific activity of FvTFL1 provides a mechanism through which woodland strawberry integrates temperature signals to balance developmental plasticity of the primary growth axis with the robustness of lateral branches.