Networking by small-molecule hormones in plant immunity

Abstract

Plants live in complex environments in which they intimately interact with a broad range of microbial pathogens and insect herbivores with different lifestyles and infection or feeding strategies. The evolutionary arms race between plants and their attackers provided plants with a sophisticated defense system that, like the animal innate immune system, recognizes the attacker and responds by activating specific defenses that are specifically directed against the invader. Recent advances in plant immunity research provided exciting new insights into the underlying defense signaling network. Diverse small-molecule hormones play pivotal roles in the regulation of this network. Their signaling pathways cross-communicate in an antagonistic or synergistic manner, providing the plant with a powerful capacity to finely tailor its immune response to the attacker encountered. Pathogens and insects, on the other hand, can manipulate the plant’s defense signaling network for their own benefit by affecting phytohormone homeostasis to antagonize the host immune response.