Biology subjects

Medvecka, E.

Publications and source records attributed to Medvecka, E..

4 recordsLinked to original sources

bioRxiv2026

Hormone-dependent receptor docking controls calcium channel activity in plants

The phytohormone auxin is a central coordinator of plant growth and development. Besides its canonical effect on gene transcription1,2, auxin triggers an ultra-rapid calcium ion influx that initiates the root gravitropic response3. The nature of the so-called rapid auxin pathway connecting the AFB1 auxin receptor3,4 and plasma membrane calcium channels remained unknown. Here, we show that auxin induces the direct interaction of the AFB1 receptor with the CNGC14 calcium channel. As the AFB1 receptor is independent of the ubiquitin ligase complex5, the auxin-induced interaction translates into relocalization of the receptor to the plasma membrane. We identify the interaction interface and provide evidence that the docking of the receptor to the channel complex activates Ca2+ influx and triggers growth inhibition. These findings position a calcium channel as an unprecedented component of the AFB1 auxin receptor complex. The ligand-dependent localization shift of a TIR1/AFB family receptor represents a novel paradigm in signal transduction and opens the possibility of unforeseen branches of auxin signaling pathways.

plant biology↗

bioRxiv2025

POLYGALACTURONASES REGULATED BY AUXIN facilitate root cell elongation in Arabidopsis thaliana via pectin remodeling

Root cell elongation, the main driver of root growth, is tightly associated with cell wall remodeling, particularly through pectin modifications, which facilitate cell wall loosening and strengthening while maintaining structural integrity. Root cell elongation is precisely regulated by the phytohormone auxin, which has long been known to inhibit this process. The molecular pathways through which auxin influences cell wall modifications remain poorly understood. In this study, we explore the transcriptional regulation of cell wall-related genes by auxin in Arabidopsis thaliana roots. The nuclear auxin pathway altered the expression of numerous cell-wall related genes, suggesting dynamic modification of the cell wall during root cell elongation. We identified novel root-specific polygalacturonases (PGs), enzymes involved in pectin degradation, which we termed POLYGALACTURONASES REGULATED BY AUXIN (PGRAs). PGRAs are expressed specifically in the root epidermis, beginning at the elongation zone. Our results demonstrate that induction of PGRA1 expression initially promotes root cell elongation, while long term overexpression inhibits root growth. Auxin downregulates PGRA1 in the elongation zone, and plants lacking PGRAs fail to increase root growth rate in response to reduced auxin levels. This suggests that auxin downregulates PGRA expression to prevent PGRA-mediated pectin remodeling, thereby contributing to inhibition of root cell elongation. We established a novel link between auxin signaling and pectin modifications in the control of cell growth. These findings provide new insights into the molecular mechanisms through which auxin regulates root cell elongation, highlighting the role of pectin matrix modifications in this process.

plant biology↗

bioRxiv2023

The AFB1 auxin receptor controls the cytoplasmic auxin response pathway in Arabidopsis thaliana

The phytohormone auxin triggers root growth inhibition within seconds via a non-transcriptional pathway. Among members of the TIR1/AFBs auxin receptor family, AFB1 has a primary role in this rapid response. However, the unique features that confer this specific function have not been identified. Here we show that the N-terminal region of AFB1, including the F-box domain and residues that contribute to auxin binding, are essential and sufficient for its specific role in the rapid response. Substitution of the N-terminal region of AFB1 with that of TIR1 disrupts its distinct cytoplasm-enriched localization and activity in rapid root growth inhibition. Importantly, the N-terminal region of AFB1 is indispensable for auxin-triggered calcium influx which is a prerequisite for rapid root growth inhibition. Furthermore, AFB1 negatively regulates lateral root formation and transcription of auxin-induced genes, suggesting that it plays an inhibitory role in canonical auxin signaling. These results suggest that AFB1 may buffer the transcriptional auxin response while it regulates rapid changes in cell growth that contribute to root gravitropism.

plant biology↗

bioRxiv2022

The AUX1-AFB1-CNGC14 module establishes longitudinal root surface pH profile

Plant roots navigate in the soil environments following the gravity vector. Cell divisions in the meristem and rapid cell growth in the elongation zone propel the root tips through the soil. Actively elongating cells acidify their apoplast to enable cell wall extension by the activity of plasma membrane AHA H+-ATPases. The phytohormone auxin, central regulator of gravitropic response and root development, inhibits root cell growth, likely by rising the pH of the apoplast. However, the role of auxin in the regulation of the apoplastic pH gradient along the root tip is unclear. Here we show, by using an improved method for visualization and quantification of root surface pH, that the Arabidopsis thaliana root surface pH shows distinct acidic and alkaline zones, which are not primarily determined by the activity of AHA H+-ATPases. Instead, the distinct domain of alkaline pH in the root transition zone is controlled by a rapid auxin response module, consisting of the AUX1 auxin influx carrier, the AFB1 auxin co-receptor and the CNCG14 calcium channel. We demonstrate that the rapid auxin response pathway is required for an efficient navigation of the root tip.

plant biology↗