Complex regulation of RETINOBLASTOMA-RELATED's interactions with E2Fs via phosphorylation
Authors: Magyar, Z., Pettko-Szandtner, A., Vadai-Nagy, F., Gombos, M., Hlacs, A., Molnar, E., Marton, A., Vizler, C., Shiekh Bin Hamid, R., Kalo, P., Feher, A.
The study maps CDK-mediated phosphorylation of Arabidopsis RBR, revealing that while many phosphorylated forms still bind E2Fs, multi‑phosphorylated RBR with a phosphorylated S911 site loses association with E2Fs and DREAM components and instead binds RNA‑binding proteins linked to ribosome biogenesis and translation. S911 phosphorylation is enriched in proliferating cells and rapidly declines after DNA damage, suggesting it switches RBR from a proliferation to a quiescence role, and molecular modeling indicates this site becomes inaccessible when RBR is complexed with E2Fs.
The study used genome‑wide ribosome profiling together with RNA‑seq to dissect translational regulation during the shift from seed dormancy to germination in Arabidopsis thaliana. It found that dormant seeds maintain a poised translational state with ribosomes pre‑positioned on stored mRNAs, and that selective changes in translational efficiency—particularly involving uORF‑mediated repression—drive germination independent of transcript levels. Functional assays confirmed that specific uORFs act as translational checkpoints during early imbibition.
The study reveals that the microtubule-associated protein MAP70-2 integrates mechanical and biochemical signals to guide division plane orientation during early lateral root primordium formation in Arabidopsis thaliana. Dynamic MAP70-2 localization to cell corners and the cortical division zone precedes cytokinesis, and loss of MAP70-2 results in misoriented divisions and malformed lateral roots, highlighting its role in three‑dimensional differential growth under mechanical constraints.
Botrytis cinerea mutants engineered to constitutively express the salicylate‑hydroxylase NahG grew better on salicylic‑acid media and showed heightened virulence on Arabidopsis thaliana and Phaseolus vulgaris, an effect that required host SA biosynthesis. Genomic analysis identified four fungal salicylate‑hydroxylase‑like genes whose expression varied during infection, suggesting B. cinerea can degrade host SA to promote colonization.
The study generated a dataset of 420 sgRNAs targeting promoters, exons, and introns of 137 tomato genes in protoplasts, linking editing efficiency to chromatin accessibility, genomic context, and sequence features. Open chromatin sites showed higher editing rates, while transcriptional activity had little effect, and a subset of guides produced near‑complete editing with microhomology‑mediated deletions. Human‑trained prediction models performed poorly, highlighting the need for plant‑specific guide design tools.
The study reveals that the Kelch phosphatase BSU1, previously thought to act as a tyrosine phosphatase in brassinosteroid signaling, actually functions as a PP1-like serine/threonine phosphatase whose activity is inhibited by CDK-mediated phosphorylation of its C‑terminal tail. Structural analysis, mutagenesis, and genetic experiments in Arabidopsis and Marchantia demonstrate that this regulatory mechanism links BSU1 to cell‑cycle control, affecting stomatal patterning, fertility, and undifferentiated cell mass formation.
The study characterizes the chloroplast‑localized protein AT4G33780 in Arabidopsis thaliana using CRISPR/Cas9 knockout and overexpression lines, revealing tissue‑specific expression and context‑dependent effects on seed germination, seedling growth, vegetative development, and root responses to nickel stress. Integrated transcriptomic (RNA‑seq) and untargeted metabolomic analyses show extensive transcriptional reprogramming—especially of cell‑wall genes—and altered central energy metabolism, indicating AT4G33780 coordinates metabolic state with developmental regulation rather than controlling single pathways.
The study re-analyzed AtGenExpress microarray data to profile expression of Arabidopsis papain-like cysteine proteases (PLCPs) and cystatins under bacterial infection, wounding, and drought, and performed in vitro assays to determine cystatin inhibition specificity for abundant PLCPs. Integrating co‑expression and inhibition data with support vector machine modeling revealed distinct PLCP‑cystatin modules for virulent versus avirulent bacterial infections and overlapping modules between drought and basal defense, indicating shared regulatory programs across stress types.
The study investigated the role of the ABA transporter NPF4.6 in Arabidopsis thaliana by analyzing loss-of-function mutants under steady and fluctuating light. Mutants displayed faster stomatal opening, higher CO2 assimilation, and increased shoot biomass under well‑watered, dynamic‑light conditions, while showing no advantage under drought stress, indicating NPF4.6 fine‑tunes stomatal kinetics in variable light environments.
The study investigates the role of the SNF1-related kinase 1 (SnRK1) in conferring quantitative resistance to clubroot disease caused by Plasmodiophora brassicae in Arabidopsis thaliana. Increased nuclear SnRK1 activity suppresses disease development by down‑regulating sucrose transporter and cell wall invertase expression and activity, thereby reducing sink strength, while the pathogen effector PBZF1 interferes with SnRK1 nuclear translocation.