A moss N-Acetyltransferase-MAPK protein controls 2D to 3D developmental transition via acetylation and phosphorylation changes
Authors: de Luxan Hernandez, C., Ammitsoe, T. J., Kanne, J. V., Stanimirovic, S., Roux, M., Weeks, Z., Schutzbier, M., Dürnberger, G., Roitinger, E., Zhang, L., Spadiut, O., Ishikawa, M., Hasebe, M., Moody, L., Dagdas, Y., Rodriguez, E., Petersen, M.
The study identifies a moss‑specific fusion protein, Rosetta NATD‑MAPK 1 (RAK1), that combines a MAPK domain with an N‑acetyltransferase and demonstrates that its acetyltransferase activity is enhanced upon MAPK activation. Knockout of RAK1 impairs the 2D‑to‑3D developmental transition in Physcomitrium patens, and mass‑spectrometry reveals associated changes in acetylation and phosphorylation linked to metabolic reprogramming.
The study examines how the SnRK1 catalytic subunit KIN10 integrates carbon availability with root growth regulation in Arabidopsis thaliana. Loss of KIN10 reduces glucose‑induced inhibition of root elongation and triggers widespread transcriptional reprogramming of metabolic and hormonal pathways, notably affecting auxin and jasmonate signaling under sucrose supplementation. These findings highlight KIN10 as a central hub linking energy status to developmental and environmental cues in roots.
The study reveals that a conserved serine adjacent to the catalytic glutamate in TIR domains is essential for NAD+‑cleaving activity, and that phosphorylation of this serine by plant calcium‑dependent protein kinases (CPKs) or mammalian kinases (CAMK2D, TBK1) inhibits the activity, thereby preventing growth repression and cell death. This phosphorylation-based mechanism provides a universal means to balance growth and immune defense across species.
The study identifies RAF24, a B4 Raf-like MAPKKK, as a novel regulator of flowering time in Arabidopsis, demonstrating that RAF24 controls the phosphorylation of the ubiquitin ligase HUB2 via SnRK2 kinases, thereby modulating H2Bub1 levels. Phospho‑mimetic and phospho‑ablative HUB2 mutants confirm that phosphorylation at S314 is critical for proper flowering timing.
The study investigated how Arabidopsis thaliana SR protein kinases (AtSRPKs) regulate alternative RNA splicing by using chemical inhibitors of SRPK activity. Inhibition with SPHINX31 and SRPIN340 caused reduced root growth and loss of root hairs, accompanied by widespread changes in splicing and phosphorylation of genes linked to root development and other cellular processes. Multi‑omics analysis (transcriptomics and phosphoproteomics) revealed that AtSRPKs modulate diverse splicing factors and affect the splicing landscape of numerous pathways.
The study investigates the role of the Arabidopsis transcription factor AtMYB93 in sulfur (S) signaling and root development, revealing that AtMYB93 mutants exhibit altered expression of S transport and metabolism genes and increased shoot S levels, while tomato plants overexpressing SlMYB93 show reduced shoot S. Transcriptomic profiling, elemental analysis, and promoter activity assays indicate that AtMYB93 contributes to root responses to S deprivation, though functional redundancy masks clear phenotypic effects on lateral and adventitious root formation.
The study investigates the Arabidopsis ribosomal protein RPS6A and its role in auxin‑related root growth, revealing that rps6a mutants display shortened primary roots, fewer lateral roots, and defective vasculature that are not rescued by exogenous auxin. Cell biological observations and global transcriptome profiling show weakened auxin signaling and reduced levels of PIN auxin transporters in the mutant, indicating a non‑canonical function of the ribosomal subunit in auxin pathways.
The study uncovers a feedback mechanism wherein phosphomimic mutation (PetD T4E) or deletion of the N‑terminal five amino acids of the b6f subunit PetD suppresses STT7 kinase activity, leading to a State 1‑locked phenotype and impaired electron transfer, highlighting the essential regulatory role of the PetD N‑terminus in photosynthetic state transitions.