Divergent Roles of CPK28 in Immune Homeostasis Across Land Plants
Abstract
Calcium-dependent protein kinases decode cellular calcium transients and play diverse roles in plant growth and stress responses. In Arabidopsis thaliana, AtCPK28 contributes to immune homeostasis by phosphorylating subgroup IV plant U-box proteins, which target the key immune receptor-like cytoplasmic kinase AtBIK1 for turnover. Here, we present functional analysis of MpCPK28 in the liverwort Marchantia polymorpha. We identify the subgroup IV plant U-box protein MpPUB20e as a substrate of MpCPK28 and provide evidence that MpPBLa (the functional ortholog of AtBIK1) undergoes proteasomal degradation and can be ubiquitinated by MpPUB20e. Interestingly, although loss of CPK28 function in multiple angiosperm species results in enhanced immune signaling, we found that Marchantia Mpcpk28 mutant alleles do not display enhanced immune-triggered production of reactive oxygen species or resistance to two pathogens. However, transgenic expression of MpCPK28 is able to restore function in Arabidopsis cpk28-1 mutants, suggesting latent functional conservation of MpCPK28. Furthermore, although AtCPK28-mediated phosphorylation of Thr95/94 on AtPUB25/26 is known to contribute to their activation, we did not observe a functional role for the equivalent residue Thr122 on MpPUB20e. Taken together, our results suggest that post-translational fine-tuning by CPK28 is likely to have refined the “PUB-BIK1” module in the vascular plant lineages. [Formula: see text] Copyright © 2026 The Author(s). This is an open access article distributed under the CC BY-NC-ND 4.0 International license .
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BibTeX
@article{dou2026divergent,
title = {{Divergent Roles of CPK28 in Immune Homeostasis Across Land Plants}},
author = {Ruoqi Dou and Baptiste Castel and Cailun a S Tanney and Virginia Natali Miguel and Melissa Bredow and Katharina Melkonian and Maria Camila Rodriguez Gallo and Jean Keller and Márcia Gonçalves-Dias and Karima El Mahboubi and Jiashu Chu and Thomas A Defalco and Cyril Zipfel and R. Glen Uhrig and Pierre-Marc Delaux and Jacqueline Monaghan},
journal = {Molecular Plant-Microbe Interactions},
year = {2026},
month = oct,
doi = {10.1094/mpmi-02-26-0020-sc},
url = {https://hal.science/hal-05782710v1},
note = {CC BY-NC-ND 4.0},
}
RIS
TY - JOUR
TI - Divergent Roles of CPK28 in Immune Homeostasis Across Land Plants
AU - Ruoqi Dou
AU - Baptiste Castel
AU - Cailun a S Tanney
AU - Virginia Natali Miguel
AU - Melissa Bredow
AU - Katharina Melkonian
AU - Maria Camila Rodriguez Gallo
AU - Jean Keller
AU - Márcia Gonçalves-Dias
AU - Karima El Mahboubi
AU - Jiashu Chu
AU - Thomas A Defalco
AU - Cyril Zipfel
AU - R. Glen Uhrig
AU - Pierre-Marc Delaux
AU - Jacqueline Monaghan
PY - 2026
DA - 2026/10/07
JO - Molecular Plant-Microbe Interactions
DO - 10.1094/mpmi-02-26-0020-sc
UR - https://hal.science/hal-05782710v1
AB - Calcium-dependent protein kinases decode cellular calcium transients and play diverse roles in plant growth and stress responses. In Arabidopsis thaliana, AtCPK28 contributes to immune homeostasis by phosphorylating subgroup IV plant U-box proteins, which target the key immune receptor-like cytoplasmic kinase AtBIK1 for turnover. Here, we present functional analysis of MpCPK28 in the liverwort Marchantia polymorpha. We identify the subgroup IV plant U-box protein MpPUB20e as a substrate of MpCPK28 and provide evidence that MpPBLa (the functional ortholog of AtBIK1) undergoes proteasomal degradation and can be ubiquitinated by MpPUB20e. Interestingly, although loss of CPK28 function in multiple angiosperm species results in enhanced immune signaling, we found that Marchantia Mpcpk28 mutant alleles do not display enhanced immune-triggered production of reactive oxygen species or resistance to two pathogens. However, transgenic expression of MpCPK28 is able to restore function in Arabidopsis cpk28-1 mutants, suggesting latent functional conservation of MpCPK28. Furthermore, although AtCPK28-mediated phosphorylation of Thr95/94 on AtPUB25/26 is known to contribute to their activation, we did not observe a functional role for the equivalent residue Thr122 on MpPUB20e. Taken together, our results suggest that post-translational fine-tuning by CPK28 is likely to have refined the “PUB-BIK1” module in the vascular plant lineages. [Formula: see text] Copyright © 2026 The Author(s). This is an open access article distributed under the CC BY-NC-ND 4.0 International license .
SN - 0894-0282
SN - 1943-7706
ER -