|Oh, Man Ho|
|Wang, Xiaofeng -|
|Clouse, Steven -|
Submitted to: American Society of Plant Biologists Annual Meeting
Publication Type: Abstract Only
Publication Acceptance Date: June 1, 2009
Publication Date: July 18, 2009
Citation: Oh, M., Wang, X., Clouse, S.D., Huber, S.C. 2009. 14-3-3 Proteins Bind to the Brassinosteroid Receptor Kinase, BRI1 and are Positive Regulators of Brassinosteroid Signaling [abstract]. American Society of Plant Biologists Annual Meeting. Paper No. P35029. Technical Abstract: Multiple members of the 14-3-3 protein family have been found in all eukaryotes, the biological functions of which are to interact physically with specific client proteins and thereby effect a change in the client. Thus, 14-3-3s are involved in many processes. The plant brassinosteroid (BR) receptor, BRASSINOSTEROID INSENSITIVE 1 (BRI1), is a member of the large family of leucine-rich repeat receptor-like kinases (LRR-RLKs) that contain cytoplasmic protein kinase domains. At least two LRR-RLKs are involved in BR perception and signal transduction: BRI1 and BRI1-associated receptor kinase 1 (BAK1). Pharmacological and molecular genetic results suggested that 14-3-3s are positive regulators of BR signaling. 14-3-3 proteins CO-IP with BRI1-Flag and both BRI1 and BAK1 bind to 14-3-3 proteins in vitro. The binding of recombinant 14-3-3<omega> to the recombinant cytoplasmic domain of BRI1 and BAK1 in vitro is dependent on autophosphorylation of the receptor kinase and is strongly stimulated by Mg2+. Generally, 14-3-3 proteins bind to pSer/pThr sites of client proteins. We determined that 14-3-3<omega> binds to the juxtamembrane domain of BRI1-CD and mutagenesis analysis suggest that Ser-858 and Thr-872 are involved in 14-3-3 binding and are critical for plant growth and development in BR signaling. The potential for serine and threonine phosphorylation to be directly involved in 14-3-3 binding is established, and adds a new dimension to the functionality of these signaling proteins.