Molecular mechanism for the interaction between gibberellin and brassinosteroid signaling pathways in Arabidopsis

Abstract

Plant development is modulated by the convergence of multiple environmental and endogenous signals, and the mechanisms that allow the integration of different signaling pathways is currently being unveiled. A paradigmatic case is the concurrence of brassinosteroid (BR) and gibberellin (GA) signaling in the control of cell expansion during photomorphogenesis, which is supported by physiological observations in several plants but for which no molecular mechanism has been proposed. In this work, we show that the integration of these two signaling pathways occurs through the physical interaction between the DELLA protein GAI, which is a major negative regulator of the GA pathway, and BRASSINAZOLE RESIS-TANT1 (BZR1), a transcription factor that broadly regulates gene expression in response to BRs. We provide biochemical evidence, both in vitro and in vivo, indicating that GAI inactivates the transcriptional regulatory activity of BZR1 upon their interaction by inhibiting the ability of BZR1 to bind to target promoters. The physiological relevance of this interaction was confirmed by the observation that the dominant gai-1 allele interferes with BR-regulated gene expression, whereas the bzr1-1D allele displays enhanced resistance to DELLA accumulation during hypocotyl elongation. Because DELLA proteins mediate the response to multiple environmental signals, our results provide an initial molecular framework for the integration with BRs of additional pathways that control plant development.cross-regulation | growth

Molecular mechanism of strigolactone perception by DWARF14

“…7). Direct interactions of DELLA proteins with other hormone signalling factors, such as JAZs and BZR1, have recently been reported to mediate the crosstalk between GA and JA signalling 33,34 , and between GA and brassinosteroid signalling 35,36 , respectively, indicating a pivotal role of DELLAs in regulating multiple signals. Our results suggest that the D14 À DELLA interaction mediates the crosstalk between GA and SL signalling pathways.…”

“…S1c). In addition, recent reports suggest that a transcription factor, which broadly regulates brassinosteroid signalling, BZR1, mediates growth response to GA via direct interaction with DELLAs 35,36 . These reports indicate that DELLAs have a role in regulating multiple signals.…”

Identification and characterization of the BZR transcription factor family and its expression in response to abiotic stresses in Zea mays L.

“…The remaining genes (ZmBZR1, ZmBZR4, ZmBZR5, ZmBZR9, ZmBZR10 and ZmBZR11) were ubiquitously expressed in all the tissues examined, suggesting that they could function as growth regulators during maize development. In fact, recent studies have demonstrated that BR signaling pathway is required to regulate hypocotyl cell expansion (Gallego-Bartolomé et al 2012;Li et al 2012;Oh et al 2012), as well as, to promote the transition from meristematic cells to primordial cells in the shoot (Oh et al 2011;Zhiponova et al 2013). In the root apex, BRs are further involved in controlling root growth, both coordinating root meristem size and also root cell elongation Heyman et al 2013;Vilarrasa-Blasi et al 2014;Vragovic et al 2015).…”

Large-Scale Identification of Gibberellin-Related Transcription Factors Defines Group VII ETHYLENE RESPONSE FACTORS as Functional DELLA Partners

“…It was previously shown that RGA interacts with PIF4 through a region encompassing its DNA binding domain, impairing PIF4 DNA binding (de Lucas et al, 2008). Other TFs also interact with DELLAs through specific parts of the protein (for instance, BRASSINAZOL RESISTANT1 [BZR1; Gallego-Bartolomé et al, 2012] or MYC2 [Hong et al, 2012]). We prepared four deleted versions of RAP2.3 ( Fig.…”

“…For instance, this is the case for several PIFs (de Lucas et al, 2008;Feng et al, 2008;Cheminant et al, 2011;Gallego-Bartolomé et al, 2011) and BZR1 (Bai et al, 2012;Gallego-Bartolomé et al, 2012;Li et al, 2012). In other cases, the interaction with the TF occurs in the vicinity of the promoters of certain genes to promote their expression (Lim et al, 2013;Park et al, 2013).…”