Fertilization of an egg by multiple sperm (polyspermy) leads to lethal genome imbalance and chromosome segregation defects. In Arabidopsis thaliana , the block to polyspermy is facilitated by a mechanism that prevents polytubey (the arrival of multiple pollen tubes to one ovule). We show here that FERONIA, ANJEA, and HERCULES RECEPTOR KINASE 1 receptor-like kinases located at the septum interact with pollen tube–specific RALF6, 7, 16, 36, and 37 peptide ligands to establish this polytubey block. The same combination of RALF (rapid alkalinization factor) peptides and receptor complexes controls pollen tube reception and rupture inside the targeted ovule. Pollen tube rupture releases the polytubey block at the septum, which allows the emergence of secondary pollen tubes upon fertilization failure. Thus, orchestrated steps in the fertilization process in Arabidopsis are coordinated by the same signaling components to guarantee and optimize reproductive success.
Phase separation of proteins/nucleic acids to form non‐membrane organelles is crucial in cellular gene‐expression regulation. However, little is known about transcriptional regulator phase separation and the underlying molecular mechanism. Vernalization 1 (VRN1) encodes a crucial transcriptional repressor involved in plant vernalization that contains two B3 DNA‐binding domains connected by an intrinsic disorder region (IDR) and nonspecifically binds DNA. We found that the Arabidopsis VRN1 protein undergoes liquid–liquid phase separation (LLPS) with DNA that is driven by multivalent protein–DNA interactions (LLPS), and that both B3 domains are required. The distribution of charged residues in the VRN1 IDR modulates the interaction strength between VRN1 and DNA, and changes in the charge pattern lead to interconversion between different states (precipitates, liquid droplets, and no phase separation). We further showed that VRN1 forms puncta in plant cell nuclei, suggesting that it may stabilize the vernalized state by repressing gene expression through LLPS.
Phase separation of proteins/nucleic acids to form non-membrane organelles is crucial in cellular gene-expression regulation. However,l ittle is knowna bout transcriptional regulator phase separation and the underlying molecular mechanism. Vernalization 1( VRN1) encodes ac rucial transcriptional repressor involved in plant vernalization that contains two B3 DNA-binding domains connected by an intrinsic disorder region (IDR) and nonspecifically binds DNA. We found that the Arabidopsis VRN1 protein undergoes liquid-liquid phase separation (LLPS) with DNAt hat is driven by multivalent protein-DNAinteractions (LLPS), and that both B3 domains are required. The distribution of charged residues in the VRN1 IDR modulates the interaction strength between VRN1 and DNA, and changes in the charge pattern lead to interconversion between different states (precipitates, liquid droplets,a nd no phase separation). We further showed that VRN1 forms puncta in plant cell nuclei, suggesting that it may stabilizethe vernalized state by repressing gene expression through LLPS.
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