Divergent roles of CPK28 in immune homeostasis across land plants
Bibliographic record
Abstract
Abstract Calcium-dependent protein kinases (CDPKs) decode cellular calcium transients and play diverse roles in plant growth and stress responses, including immunity. In Arabidopsis thaliana (At, Arabidopsis thereafter), AtCPK28 contributes to immune homeostasis by phosphorylating subgroup IV plant U-box proteins AtPUB22/24/25/26, which target the key immune receptor-like cytoplasmic kinase (RLCK) AtBIK1 for turnover. While this module is conserved in multiple angiosperms, it is unclear if the role of CPK28 in immune homeostasis is conserved more broadly across land plants. Here, we took an evolutionary comparative approach to understand the role of CPK28. We identified a single CPK28 ortholog in the liverwort Marchantia polymorpha , MpCPK28, which exhibits Ca 2+ -dependent kinase activity that is inhibited by calmodulin in vitro . We identified the subgroup IV plant U-box protein MpPUB20e as a substrate of MpCPK28. MpPUB20e is able to ubiquitinate MpPBLa, the functional ortholog of AtBIK1. We also provide preliminary evidence that MpPBLa undergoes proteasomal degradation in Marchantia, suggesting that optimization of MpPBLa protein accumulation is conserved across land plants. Interestingly, while loss of CPK28 function in multiple angiosperm species results in enhanced immune signaling, we find 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 was able to restore function in Arabidopsis cpk28-1 mutants, suggesting latent functional conservation of MpCPK28. Furthermore, while AtCPK28-mediated phosphorylation of Thr95/94 on AtPUB25/26 is known to contribute to their activation, we could 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.
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How this classification was reachedexpand
Full frame machine prediction
Teacher imitationNot calibrated prevalence, not ground truth. Human validation pending. The Gemma side is a direct model label for every work in the frame, read from the title-only record. The Codex side is a classifier learned from the 10,348 direct Codex labels and calibrated to design-weighted sample rates; fields without enough sample support carry no Codex call. Candidate is the union of the two sides; consensus is their intersection. These outputs are machine_predicted_unvalidated and are not human labels.
Distilled classifier scores by category (both heads)
| Category | Codex | Gemma |
|---|---|---|
| Metaresearch | 0.000 | 0.000 |
| Meta-epidemiology (narrow) | 0.000 | 0.000 |
| Meta-epidemiology (broad) | 0.000 | 0.000 |
| Bibliometrics | 0.000 | 0.000 |
| Science and technology studies | 0.000 | 0.000 |
| Scholarly communication | 0.000 | 0.000 |
| Open science | 0.000 | 0.000 |
| Research integrity | 0.000 | 0.000 |
| Insufficient payload (model declined to judge) | 0.001 | 0.000 |
Machine scores (provisional)
The two teacher heads of the student model, read on this work. A score orders the frame for review; it never asserts a category, and the validation status ships verbatim with every row.
Baseline scores from an immature model (maturity gate not passed, 7 training rounds). Scores rank; they never assert a category.
score_only:v0-immature-baseline · verbatim from the scoring run: score_only means the number may rank works, and no category label ships from itClassification
machine, unvalidatedMachine predicted; a candidate call from one source (direct Gemma or distilled Codex), not a consensus.
How this classification was reached, model by model and score by score, is at the end of the page under "How this classification was reached".