Immune activation suppresses reproductive growth in Arabidopsis through cytokinin signaling

Plants constantly integrate environmental stimuli with developmental programs to optimize their growth and fitness. Excessive activation of the plant immune system often leads to decreased plant growth, a process known as the growth-defense tradeoff. Cytokinins are phytohormones that regulate cell division and plant yield, with important additional roles in nitrogen signaling and abiotic and biotic stress tolerance. Here, we show that constitutive activation of immunity suppresses cytokinin signaling and that complementation of the levels of cytokinin in Arabidopsis autoimmunity mutants reduces the growth tradeoff due to defense activation by changes in meristematic activity, resulting in increased yield and resistance to pathogens of both the biotrophic and necrotrophic lifestyles. Thus, complementation of cytokinin suppression in the context of activated immunity may be targeted for increased crop productivity and resistance through genetic and chemical means. Our approach demonstrates targeting of phytohormone crosstalk for alleviating the growth-defense tradeoff, bypassing laborious and time-consuming identification and manipulation of causal genes, and indicates that similar approaches may be used for optimization of other traits in plants.