Linking Brassinosteroid and ABA Signaling in the Context of Stress Acclimation

Abstract

The important regulatory role of brassinosteroids (BRs) in the mechanisms of tolerance to multiple stresses is well known. Growing data indicate that the phenomenon of BR-mediated drought stress tolerance can be explained by the generation of stress memory (the process known as ‘priming’ or ‘acclimation’). In this review, we summarize the data on BR and abscisic acid (ABA) signaling to show the interconnection between the pathways in the stress memory acquisition. Starting from brassinosteroid receptors brassinosteroid insensitive 1 (BRI1) and receptor-like protein kinase BRI1-like 3 (BRL3) and propagating through BR-signaling kinases 1 and 3 (BSK1/3) → BRI1 suppressor 1 (BSU1) ―‖ brassinosteroid insensitive 2 (BIN2) pathway, BR and ABA signaling are linked through BIN2 kinase. Bioinformatics data suggest possible modules by which BRs can affect the memory to drought or cold stresses. These are the BIN2 → SNF1-related protein kinases (SnRK2s) → abscisic acid responsive elements-binding factor 2 (ABF2) module; BRI1-EMS-supressor 1 (BES1) or brassinazole-resistant 1 protein (BZR1)–TOPLESS (TPL)–histone deacetylase 19 (HDA19) repressor complexes, and the BZR1/BES1 → flowering locus C (FLC)/flowering time control protein FCA (FCA) pathway. Acclimation processes can be also regulated by BR signaling associated with stress reactions caused by an accumulation of misfolded proteins in the endoplasmic reticulum.

Control of ABA Signaling and Crosstalk with Other Hormones by the Selective Degradation of Pathway Components

“…BR signaling has recently attracted attention [ 17 , 176 , 177 , 178 , 179 ]. The cross-regulation of ABA- and BR-signaling pathways is marked in Figure 5 B. BRASSINOSTEROID-INSENSITIVE 2 (BIN2) interacts with central components of the ABA signaling pathway, such as bZIP transcription factor ABI5 [ 180 ] and protein phosphatase 2C ABI1 [ 181 ], and phosphorylates SNF1-related protein kinases SnRK2.2 and SnRK2.3 [ 182 ].…”

“…Conventional degradation of the tagged components takes place via the proteasome; however, increasing evidence demonstrates a significant role of autophagy in controlling ABA signaling [ 9 , 12 , 13 , 14 , 15 , 16 ]. In addition to this interplay with degradation systems, an additional layer of complexity is provided by extensive crosstalk between ABA and other phytohormones [ 17 , 18 , 19 , 20 ].…”

Control of ABA Signaling and Crosstalk With Other Hormones by Selective Degradation of Pathway Components

“…A fragment of the CK signaling pathway with ABA-CKs-autophagy interplay is illustrated in Figure 5A. BR signaling has recently attracted attention (for reviews [17,[176][177][178][179]). The cross-regulation of ABA-and BR-signaling pathways is marked in Figure 5B.…”

“…Conventional degradation of the tagged components takes place via the proteasome; however, increasing evidence demonstrates a significant role of autophagy in controlling ABA signaling (for recent reviews [9,[12][13][14][15][16]). In addition to this interplay with degradation systems, an additional layer of complexity is provided by extensive crosstalk between ABA and other phytohormones (for reviews [17][18][19][20]).…”

Cell Signaling in Model Plants

“…BRs have many interactions with other phytohormones that regulate the downstream pathways related to plant growth or response to stresses. Bulgakov and Avramenko reviewed the links between BR and abscisic acid (ABA) signaling that affect the stress-acclimation processes [ 10 ]. They proposed three interconnected mechanisms that in the first mechanism, BIN2, as a kinase of BR signaling, is responsible for interaction with ABA signaling.…”