BES1 hinders ABSCISIC ACID INSENSITIVE5 and promotes seed germination in Arabidopsis

Abstract

Proper regulation of seed germination is essential for the successful propagation of a plant. The transcription factor ABSCISIC ACID INSENSITIVE5 (ABI5) of the abscisic acid (ABA) signaling pathway plays a central role in the inhibition of seed germination. ABI5 is precisely regulated by the core ABA signaling components and multiple other factors. However, the complex regulatory network of ABI5 remains largely unknown. In this study, we determined the biochemical interaction between ABI5 and the BRINSENSITIVE1 (BRI1)-EMS-SUPPRESSOR1 (BES1) transcription factor of the brassinosteroid (BR) signaling pathway, as well as the function of BES1 regulating ABI5 during seed germination in Arabidopsis. BES1 directly interacts with ABI5 both in vitro and in vivo. The bZIP domain of ABI5, which is responsible for DNA binding, is critical for ABI5 binding to BES1. The interaction of BES1 with ABI5 significantly suppressed the binding of ABI5 to the promoter regions of downstream genes, which resulted in their reduced expression and consequently facilitated seed germination. This study shed new light on the coordination of multiple signaling pathways during seed germination. In particular, BES1 directly binds to ABI5, which interferes with its transcriptional activity and suppresses ABA signaling output.

StABI5 Involved in the Regulation of Chloroplast Development and Photosynthesis in Potato

“…The ABA signaling pathway is a complex signaling network that integrates with other signaling pathways including BR, CK, JA, GA and auxin signals. Many studies have shown that ABI5, as a key positive transcription factor in the ABA signaling pathway, not only responds to ABA to regulate the expression of ABA-responsive genes, but also participates in the regulation of other plant hormone signaling pathways [10,33,41,42]. Components of auxin, CK, GA, JA and BR signals were shown to take part in ABI5 regulation or to be regulated by ABI5 [10,33,41,42].…”

“…The brassinosteroid insensitive 2 (BIN2) kinase, a key repressor of brassinosteroid (BR) signaling, has been shown to phosphorylate and stabilize ABI5 during seed germination [9]. By contrast, the brassinazole resistant 1 (BZR1) and BR insensitive 1-EMS-suppressor 1 (BES1) transcription factors of the BR signaling pathway can suppress ABI5 transcriptional activity and promote seed germination in Arabidopsis [10,11]. Similarly, DELLA proteins of gibberellic acid (GA) signaling promote the transcriptional activity of ABI5 to inhibit seed germination and postgerminative growth, whereas the transcription factor inducer of CBF expression 1 (ICE1) interferes with the transcriptional function of ABI5 and promotes seed germination [12,13].…”

Balancing growth and adaptation to stress: Crosstalk between brassinosteroid and abscisic acid signaling

“…Further study has revealed that BES1 interacts with the bZIP domain of ABI5,hindering the association of ABI5 to its target promoters and suppressing the transcription of ABI5 downstream genes (Zhao, Dou, Gong, Wang, & Mao, 2019). Moreover, ABI3 and ABI5 form heterodimers and co‐regulate a series of genes (Nakamura, Lynch, & Finkelstein, 2001; Tezuka, Taji, Hayashi, & Sakata, 2013).…”

GSK3‐like kinase BIN2 phosphorylates RD26 to potentiate drought signaling in Arabidopsis

“…At the TFs level, BES1 can repress ABI3 by recruiting TOPLESS and HDAC19 complex (Ryu et al ., ), and BZR1 can bind to the promoter of ABI5 to suppress its transcription (Yang et al ., ). Moreover, BES1 has been reported to directly interact with ABI5 to inhibit ABI5 binding to target gene promoters, therefore to promote seed germination (Zhao et al ., ).…”