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 corepressor 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.