The transition from vegetative growth to flower formation is critical for the survival of flowering plants. The plant-specific transcription factor LEAFY (LFY) has central, evolutionarily conserved roles in this process, both in the formation of the first flower and later in floral patterning. We performed genome-wide binding and expression studies to elucidate the molecular mechanisms by which LFY executes these roles. Our study reveals that LFY directs an intricate regulatory network in control of floral homeotic gene expression and, unexpectedly, controls the expression of genes regulating the response to external stimuli in Arabidopsis. We further show that LFY dampens responses to a bacterial MAMP (microbe-associated molecular pattern) and to pathogen challenge. Our findings suggest a molecular mechanism for the coordination of reproductive stage development and disease response programs in plants. Regulation of these distinct survival programs by a single transcription factor may ensure optimal allocation of plant resources for reproductive fitness.