Multifaceted involvement of abscisic acid in plant interactions with pathogenic and mutualistic microbes

Abstract

Abstract Over the course of coevolution, plants have acquired a number of mechanisms to adaptively respond to a wide variety of microbes including pathogens and mutualists that affect plant fitness. Although widely recognized as a central regulator in plant adaptation to abiotic stresses as well as in plant growth and development, abscisic acid (ABA) also acts as a key modulator of plant responses to microbes. Effects of ABA on plant-pathogen interactions differ depending on the stages and modes of pathogen infection, but in many cases ABA negatively regulates plant immunity. This is reflected by the fact that some pathogens produce ABA on their own or induce ABA accumulation in the infected plants to promote infection. In mutualistic plant-microbe interactions, ABA generally promotes plant colonization by arbuscular mycorrhizal fungi but suppresses that by rhizobia. ABA interacts antagonistically or synergistically with multiple signaling components that regulate plant responses to pathogens and mutualists, including jasmonic acid, ethylene, salicylic acid, gibberellin, cytokinin and mitogen-activated protein kinases. This ABA signaling network likely enables plants to integrate ABA-regulated stress responses and developmental processes into their responses to pathogens and mutualists for optimizing plant fitness. In this chapter, I review the current understanding of ABA-mediated modulation of plant interactions with pathogenic and mutualistic microbes and illuminate the underlying mechanisms with a focus on crosstalk between ABA and other signaling components.