Biology subjects

Kocourkova, D.

Publications and source records attributed to Kocourkova, D..

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↗

bioRxiv2026

The molecular architecture of the Arabidopsis callose synthase complex

ABSTRACTCallose synthase is responsible for the targeted deposition of the {beta}-1,3-glucan polymer, callose which underlines essential plant developmental processes, including cell division, pathogen defense or cell-cell communication. The architecture of the callose synthase complex (CALSC) as well as the molecular mechanisms of callose synthesis remain unknown. Here we report an integrative characterisation of the Arabidopsis CALS complex, with the most enriched subunits, CALS1, CALS2 and CALS3, forming its core. Structurally, CALSC assembles into a trimer, requiring the plant-specific Bag domain to mediate inter-subunit associations. The biological importance of CALSC assembly is highlighted by the simultaneous loss of CALS1 and CALS3, which abolishes plasmodesmal callose deposition and affects symplastic transport. Site-directed mutagenesis and molecular dynamics simulations depict the topology of the CALS1 active site in detail, including the components of the enzymatic reaction. We pinpoint the translocating tunnel through which the nascent glucan is delivered and mechanistically confirm the role of transmembrane helix 8 in regulating glucan export. Our work provides unprecedented insight into the molecular architecture of the CALSC and the distinct changes from maturation to activity at the plasma membrane, while showcasing the mechanisms involved in callose synthesis at the molecular level.

plant biology↗

bioRxiv2023

A novel workflow for unbiased quantification of autophagosomes in 3D in Arabidopsis thaliana roots

Macroautophagy is frequently quantified by live imaging of autophagosomes decorated with a marker of fluorescently tagged ATG8 protein (FT-ATG8) in Arabidopsis thaliana. This requires generation of suitable plant material by time-consuming crossing or transformation with FT-ATG8 marker. Autophagosome quantification by image analysis often relies on their counting in individual focal planes. This approach is prone to deliver biased results due to inappropriate sampling of the regions of interest in the Z-direction, as the actual 3D distribution of autophagosomes is usually not taken into account. To overcome such drawbacks, we have developed and tested a workflow consisting of immunofluorescence microscopy of autophagosomes labelled with anti-ATG8 antibody followed by stereological image analysis employing the optical disector and the Cavalieri principle. Our immunolabelling protocol specifically recognized autophagosomes in epidermal cells of A. thaliana root. Higher numbers of immunolabelled autophagosomes were observed when compared with those recognized with FT-AtATG8e marker, suggesting that single AtATG8 isoform markers cannot detect all autophagosomes in a cell. Therefore, immunolabelling provides more precise information as the anti-ATG8 antibody recognizes virtually all AtATG8 isoforms. The number of autophagosomes per tissue volume determined by stereological methods correlated with the intensity of autophagy induction treatment. Compared to autophagosome quantifications in maximum intensity projections, stereological methods detected autophagosomes present in a given volume with higher accuracy. Our novel application of immunolabelling combined with stereological methods constitutes a powerful toolbox for unbiased and reproducible quantification of autophagosomes and offers a convenient alternative to the standard of live imaging using FP-ATG8 marker.

plant biology↗

bioRxiv2021

Phospholipase Dα1 acts as a negative regulator of high Mg2+-induced leaf senescence in Arabidopsis

Magnesium is a macronutrient involved in essential cellular processes. Its deficiency or excess is a stress factor for plants, seriously affecting their growth and development and therefore, its accurate regulation is essential. Recently, we discovered that phospholipase D1 (PLD1) activity is vital in the stress response to high-magnesium conditions in Arabidopsis roots. This study shows that PLD1 acts as a negative regulator of high-Mg2+-induced leaf senescence in Arabidopsis. The level of phosphatidic acid produced by PLD1 and the amount of PLD1 in the leaves increase in plants treated with high Mg2+. A knockout mutant of PLD1 (plda1-1), exhibits premature leaf senescence under high-Mg2+ conditions. In pld1-1 plants, higher accumulation of abscisic and jasmonic acid and impaired magnesium, potassium and phosphate homeostasis were observed under high-Mg2+ conditions. High Mg2+ also led to an increase of starch and proline content in Arabidopsis plants. While the starch content was higher in plda1-1 plants, proline content was significantly lower in plda1-1 compared with WT. Our results show that PLD1 is essential for Arabidopsis plants to cope with the pleiotropic effects of high-Mg2+ stress and delay the leaf senescence.

plant biology↗