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Plant Physiol. 2016 May;171(1):71-81. doi: 10.1104/pp.15.01962. Epub 2016 Mar 9.

Gatekeeper Tyrosine Phosphorylation of SYMRK Is Essential for Synchronizing the Epidermal and Cortical Responses in Root Nodule Symbiosis.

Author information

1
Department of Biochemistry, University of Calcutta, Kolkata 700019, India (S. Saha, A.P., A.D., A.B., S. Samaddar, M.D.); andDepartment of Molecular and Structural Biochemistry, North Carolina State University, Raleigh, North Carolina 27695 (L.H., M.B.G.).
2
Department of Biochemistry, University of Calcutta, Kolkata 700019, India (S. Saha, A.P., A.D., A.B., S. Samaddar, M.D.); andDepartment of Molecular and Structural Biochemistry, North Carolina State University, Raleigh, North Carolina 27695 (L.H., M.B.G.) maitrayee_d@hotmail.com.

Abstract

Symbiosis receptor kinase (SYMRK) is indispensable for activation of root nodule symbiosis (RNS) at both epidermal and cortical levels and is functionally conserved in legumes. Previously, we reported SYMRK to be phosphorylated on "gatekeeper" Tyr both in vitro as well as in planta. Since gatekeeper phosphorylation was not necessary for activity, the significance remained elusive. Herein, we show that substituting gatekeeper with nonphosphorylatable residues like Phe or Ala significantly affected autophosphorylation on selected targets on activation segment/αEF and β3-αC loop of SYMRK. In addition, the same gatekeeper mutants failed to restore proper symbiotic features in a symrk null mutant where rhizobial invasion of the epidermis and nodule organogenesis was unaffected but rhizobia remain restricted to the epidermis in infection threads migrating parallel to the longitudinal axis of the root, resulting in extensive infection patches at the nodule apex. Thus, gatekeeper phosphorylation is critical for synchronizing epidermal/cortical responses in RNS.

PMID:
26960732
PMCID:
PMC4854696
DOI:
10.1104/pp.15.01962
[Indexed for MEDLINE]
Free PMC Article

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