Chapter 8 - Signaling crosstalk between brassinosteroids and abscisic acid in plant defense, growth, and development

Abstract

Crosstalk between signaling pathways of plant hormones occurs at multiple junctures throughout the entire lifecycle of plants. This crosstalk employs interactions among signaling components involved in the respective pathways that eventually modulate the response that is exhibited under specific conditions. Among many such interactions, the interplay of brassinosteroids (BR) and abscisic acid (ABA) pathways serve to develop a balance between growth, development, and defense responses. BR signaling helps to maintain optimal growth; however, under stressful conditions, BR signaling is dampened and ABA signaling is activated. The domination of either BR or ABA signaling determines which response is triggered. The BR and ABA signaling pathways converge at certain components downstream of BR signaling. This interaction involves the regulation of phosphorylation status and protein degradation eventually to regulate activities of downstream transcription factors. The elucidation of this interconnection of BR and ABA signaling pathways has been facilitated by vigorous investigations that led to the unraveling of several key components, such as the BR-signaling component BIN2 and the ABA signaling component ABI5. Taking into account the crucial role of BR–ABA crosstalk in balancing growth and development, this chapter brings together what is known so far about their interplay in the regulation of growth and defense responses, with a focus on the components involved.