Related Experiment Video
Updated: Apr 10, 2026

Identification of Post-translational Modifications of Plant Protein Complexes
Published on: February 22, 2014
De-repression of protein phosphatase 5 by the chaperone organizer HOP1 activates plant NLR immunity
Yan Yan1, Zhixue Zhao2, In-Cheol Yeo1
1Department of Molecular, Cellular, and Developmental Biology, University of Michigan, Ann Arbor, MI, USA.
Abstract:
Protein phosphatase 5 (PP5) is a conserved serine/threonine phosphatase regulating growth, stress responses, programmed cell death and immunity across eukaryotes. However, the mechanisms underlying its activation remain poorly understood. Here we demonstrate that the disruption of the plant MEKK1-MKK1/2-MPK4 cascade activates LET7, a plant homologue of PP5, triggering nucleotide-binding leucine-rich repeat (NLR) SUMM2-mediated autoimmunity in Arabidopsis. The binding of LET7 to the co-chaperone protein HOP1 disrupts the autoinhibitory interaction between the tetratricopeptide repeat and phosphatase domains of LET7 in releasing its phosphatase activity. Activated LET7 subsequently dephosphorylates CRCK3, a crucial kinase regulating SUMM2 autoimmunity. Furthermore, HOP1 and LET7 stabilize SUMM2 via their tetratricopeptide repeat domains, highlighting the dual role of the HOP1-LET7 module in dephosphorylating CRCK3 and stabilizing SUMM2 in NLR-mediated immunity. Our studies reveal a conserved mechanism of PP5 activation across plants and animals and elucidate a unique dephosphorylation cascade governing NLR activation.
Related Concept Videos
Cell Signaling in Plants
Regulation of the Unfolded Protein Response
Defenses Against Pathogens and Herbivores
Regulation of Nuclear Protein Sorting
Plant Hormones
MAPK Signaling Cascades

