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ARS Home » Midwest Area » Urbana, Illinois » Global Change and Photosynthesis Research » Research » Publications at this Location » Publication #223021
Title: Sequential Transphosphorylation of the BRI1/BAK1 Receptor Kinase Pair Regulates Early Events of the Brassinosteriod Signaling Pathway Promoting Plant Growth and Development

Author
item WANG, X - N CAROLINA ST UNIVERSITY
item KOTA, U - N CAROLINA ST UNIVERSITY
item HE, K - UNIVERSITY OF OKLAHOMA
item BLACKBURN, K - N CAROLINA ST UNIVERSITY
item LI, J - UNIVERSITY OF OKLAHOMA
item GOSHE, M - N CAROLINA ST UNIVERSITY
item Huber, Steven
item CLOUSE, S - N CAROLINA ST UNIVERSITY

Submitted to: Developmental Cell
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 6/1/2008
Publication Date: 8/1/2008
Citation: Wang, X., Kota, U., He, K., Blackburn, K., Li, J., Goshe, M.B., Huber, S.C., Clouse, S.D. 2008. Sequential Transphosphorylation of the BRI1/BAK1 Receptor Kinase PAir Regulates Early Events of the Brassinosteriod Signaling Pathway Promoting Plant Growth and Development. Developmental Cell. 15(2):220-235.

Interpretive Summary: Brassinosteroids (BRs) are important plant growth hormones that regulate many aspects of normal plant growth and development, including resistance to a wide range of stress conditions. It is known that BRs bind to the receptor protein known as BRASSINOSTEROID INSENSITIVE 1 (BRI1), which is a receptor kinase located in the plasma membrane. BRI1 containing bound BR then binds to its co-receptor known as BRI1-ASSOCIATED KINASE 1 (BAK1). However, the early events that follow the interaction between BRI1 and BAK1 are not clear. Our results suggest that when BAK1 binds to BRI1, the protein kinase function of BRI1 is activated allowing for autophosphorylation of itself and also phosphorylation of sites on BAK1 that are essential for BR signaling. The emerging model is simlar to, but also distinct from, receptor tyrosine kinase signaling in mammals. Increasing our understanding of the early events of BR signaling may help to understand plant receptor kinases in general, and may ultimately provide new approaches to enhance crop growth and productivity.

Technical Abstract: Brassinosteroids (BRs) regulate multiple aspects of plant growth and development through a signal transduction pathway that is initiated by BR binding to the transmembrane receptor kinase BRI1. Activated BRI1 heterodimerizes with a second receptor kinase, BAK1, leading to enhanced signaling output. The detailed molecular mechanisms of phosphorylation, kinase activation and dimerization of the BRI1/BAK1 pair in response to BR are unknown. We demonstrate that BR activation of BRI1 precedes that of BAK1 in planta and that BRI1 transphopshorylates BAK1 on specific kinase domain residues, some of which are critical for BAK1 kinase function and optimal BR signaling. BAK1 also transphosphorylates BRI1 on juxtamembrane and carboxy terminal domain residues, increasing BRI1 kinase activity towards a specific substrate. Our results are consistent with a novel sequential transphosphorylation model that clarifies early events of BR signaling and allows a direct comparison of the molecular mechanisms of plant and animal receptor kinases.