Signaling crosstalk between auxins—abscisic acid in plant defense, growth, and development

Plant hormones are structurally diverse compounds that usually act at nanomolar concentrations. They regulate several regulatory and metabolic systems, which are essential both for plant development and responses to biotic and abiotic stresses. Several researchers have illustrated the mechanism of action of individual plant hormones and processes regulated by them. Several phytohormones work via interconnected networks in response to the stimuli and regulate the growth and development of plants synergistically or antagonistically. This interpathway communication is known as hormone crosstalk. A clear understanding of these hormonal crosstalks is essential for the understanding of growth responses under different growth conditions. This chapter focuses on two phytohormones, auxin and abscisic acid. It covers a brief overview of the hormones along with synthesis, signaling, and transport of auxin and abscisic acid. It covers details of Auxin–ABA interaction on growth, development, and defense in plants. Finally, we end with a brief discussion and prospects for the field.