A negative feedback loop between TERMINAL FLOWER1 and LEAFY protects inflorescence indeterminacy

Inflorescences of flowering plants adopt diverse genetically programmed and environmentally tuned architectures. By contrast, continued maintenance of the stem-cell pool within the apical meristem is unresponsive to environmental cues. Through a combination of modeling and experimentation in Arabidopsis , we reveal a negative feedback loop that buffers environmental signals. This loop comprises the determinacy-promoting pioneer transcription factor LEAFY (LFY) and the indeterminacy-promoting transcriptional co-repressor TERMINAL FLOWER1 (TFL1). At the transition to the flower-producing reproductive phase, LFY directly and quantitatively up-regulates expression of TFL1 . TFL1 in turn negatively feeds back on LFY to prevent LFY overaccumulation. This blocks inflorescence termination even under strong florally inductive signals. Our work uncovers a mechanism for robust environmental buffering involving differential responses of two cell populations to the same environmental stimulus.