Brassinosteroid Signal Transduction: From Receptor Kinase Activation to Transcriptional Networks Regulating Plant Development

Abstract

Brassinosteroid (BR) signal transduction research has progressed rapidly from the initial discovery of the BR receptor to a complete definition of the basic molecular components required to relay the BR signal from perception by receptor kinases at the cell surface to activation of a small family of transcription factors that regulate the expression of more than a thousand genes in a BR-dependent manner. These mechanistic advances have helped answer the intriguing question of how a single molecule, such as a hormone, can have dramatic pleiotropic effects on a broad range of diverse developmental pathways and have shed light on how BRs interact with other plant hormones and environmental cues to shape the growth of the whole plant. This review summarizes the current state of BR signal transduction research and then examines recent articles uncovering gene regulatory networks through which BR influences both vegetative and reproductive development.

Jasmonate Controls Leaf Growth by Repressing Cell Proliferation and the Onset of Endoreduplication while Maintaining a Potential Stand-By Mode

“…Recently, targeted proteomics has uncovered and mapped several interactions of core cell cycle genes (Boruc et al, 2010;Van Leene et al, 2010, 2011. While our study has been informed by previous ones carried out with JA and MeJA in synchronized, actively dividing Bright Yellow-2 or Arabidopsis cell cultures ( Swiątek et al, 2002( Swiątek et al, , 2004Pauwels et al, 2008), it has revealed several differences with important physiological relevance for the whole plant system.…”

“…The cell cycle regulation machinery is tightly coordinated temporally and spatially during plant development by the action of phytohormones (Gutierrez, 2009;Gonzalez et al, 2010;Dudits et al, 2011). Several studies involving plant hormones such as auxin (PerrotRechenmann, 2010), abscisic acid ( Swiątek et al, 2002;Skirycz and Inzé, 2010), brassinosteroids (Clouse, 2011), GAs (Achard et al, 2009), or cytokinins (Haberer and Kieber, 2002) show how hormonal signaling networks are able to modulate cell division parameters to impact plant growth and development.…”

“…In terms of cellular machinery, although basic plant cell cycle and growth regulators have become increasingly well characterized during Arabidopsis development (Gutierrez, 2009;Boruc et al, 2010;Van Leene et al, 2010, 2011, little is known about their precise regulation/ coordination. It has been shown that cell cycle progression and the switch from the mitotic to the endoreduplication cycle result from the accurate and sequential activity of a conserved core set of regulators implicated in DNA replication and mitosis (Inzé and De Veylder, 2006;Gutierrez, 2009;De Veylder et al, 2011).…”

A large-scale protein phosphorylation analysis reveals novel phosphorylation motifs and phosphoregulatory networks in Arabidopsis

“…For example, four phosphoproteins in the brassinosteroid signaling pathway were identified, including the BR-signaling kinase 1 (BSK1, pSer-230), kinase BIN2 (pTyr-200), transcription factors BZR1 (pSer-173), and BES1 (pSer-171 and pThr-175). It is now known that the regulation of these proteins by phosphorylation plays important roles in brassinosteroid signaling [60,62,65]. Phosphoproteins were also identified for ethylene signaling components, including the ethylene receptor EIN4 (pThr-514, pSer-617) and the raf-like kinase CTR1 (pSer-707, 710) which are negative regulators of ethylene signaling [66], and MPK6 (pThr-221, pTyr-223) and EIN2 (pSer-655, 659, pThr-657) which are positive regulators of ethylene signaling [67].…”

Arabidopsis MICROTUBULE DESTABILIZING PROTEIN40 Is Involved in Brassinosteroid Regulation of Hypocotyl Elongation

“…Brassinosteroids (BRs) are crucial plant phytohormones that affect a wide range of developmental and physiological processes in plants, such as stem elongation and vascular differentiation (Clouse, 2011;Ye et al, 2011). BRs function through the BRI1 receptor-like kinase and a well-defined signal transduction pathway to activate two key transcription factors, BRASSI-NAZOLE-RESISTANT1 (BZR1) and BRINSENSITIVE1 (BRI1)-EMS-SUPPRESSOR1(BES1)/BZR2 (Li, 2010;Kim and Wang, 2010;Clouse, 2011;Gudesblat and Russinova, 2011).…”