RT Journal Article
SR Electronic
T1 Mechanistic analysis of the SERK3 <em>elongated</em> allele defines a role for BIR ectodomains in brassinosteroid signaling
JF bioRxiv
FD Cold Spring Harbor Laboratory
SP 257543
DO 10.1101/257543
A1 Ulrich Hohmann
A1 Joël Nicolet
A1 Andrea Moretti
A1 Ludwig A. Hothorn
A1 Michael Hothorn
YR 2018
UL http://biorxiv.org/content/early/2018/01/31/257543.abstract
AB The leucine-rich repeat receptor kinase (LRR-RK) BRI1 requires a shape-complementary SERK co-receptor for brassinosteroid sensing and receptor activation. Interface mutations that weaken the interaction between receptor and co-receptor in vitro reduce brassinosteroid signaling responses. The SERK3 elongated (elg) allele maps to the complex interface and shows enhanced brassinosteroid signaling, but surprisingly no tighter binding to the BRI1 ectodomain in vitro. Here, we report that rather than promoting the interaction with BRI1, the elg mutation disrupts the ability of the co-receptor to interact with the ectodomains of BIR receptor pseudokinases, negative regulators of LRR-RK signaling. A conserved lateral surface patch in BIR LRR domains is required for targeting SERK co-receptors and the elg allele maps to the core of the complex interface in a 1.25 Å BIR3 - SERK1 structure. Collectively, our structural, quantitative biochemical and genetic analyses suggest that brassinosteroid signaling complex formation is negatively regulated by BIR receptor ectodomains.