Biology subjects

Hlavackova, K.

Publications and source records attributed to Hlavackova, K..

4 recordsLinked to original sources

bioRxiv2026

Stomatal movement in Arabidopsis is driven by guard cell-localized and copper-insensitive CSD1 splice variant

Copper (Cu) is an essential micronutrient whose bioavailability is strongly affected by soil physicochemical properties. During evolution, plants have developed mechanisms to flexibly adjust their metabolism to Cu status. Superoxide dismutases (SODs), including Cu/ZnSOD1 (CSD1) and FeSOD1 (FSD1), are key antioxidant enzymes regulated in Cu dependent manner in Arabidopsis thaliana. Examination of CSD1 cellular distribution and activity revealed that CSD1 is a nuclear and cytosolic SOD whose abundance and activity respond to Cu availability inversely to FSD1. Combined microscopic and biochemical analyses of Cu-dependent dynamics revealed that, unlike FSD1, CSD1 localization in guard cells (GCs) remains independent of Cu availability. CSD1 escapes miR398-mediated regulation in GCs through a cell type-specific splice variant (CSD1.2) that carries an altered miR398-binding site. In silico analyses indicate that this mechanism is also present in crop species. Functionally, the csd1 mutant showed reduced sensitivity to abscisic acid (ABA)-induced stomatal closure, a phenotype rescued by reintroducing CSD1. Biochemical and reactive oxygen species (ROS) level analyses indicate that CSD1.2 most likely acts independently of its canonical enzymatic activity in GCs and functions upstream of the ROS burst in the ABA signaling pathway. Together, we present a novel, cell-type-specific mechanism that safeguards ABA-driven stomatal closure under fluctuating Cu supply.

plant biology↗

bioRxiv2025

Protein and genetic interactions between RACK1A and FSD1 modulate plant development and stress granule-dependent response to salt in Arabidopsis.

The generation of reactive oxygen species (ROS) and their regulation by antioxidant enzymes such as IRON SUPEROXIDE DISMUTASE 1 (FSD1) are critical for managing plant responses to salt stress. However, the protein networks modulating ROS levels during salt stress remain incompletely understood. Our co-immunoprecipitation analysis identified the FSD1 as an interaction partner of the scaffolding protein RECEPTOR FOR ACTIVATED C KINASE 1A (RACK1A). Bimolecular fluorescence complementation analyses revealed that RACK1A interacts with FSD1 predominantly in the cytoplasm. Despite elevated FSD1 activity in rack1a mutants, the abundance of FSD1 protein remained unchanged. Computational predictions of interaction interfaces suggested that RACK1A may interfere with the catalytic site of FSD1. Advanced fluorescence microscopy and genetic studies further confirmed localization and relocation patterns of RACK1A and FSD1 during salt stress responses. Additionally, we found that the RACK1A-FSD1 module was involved in root hair tip growth, highlighting the developmental significance of this interaction. While rack1a mutants exhibited salt resilience, fsd1-1 rack1a-1 double mutant displayed reduced salt stress resistance compared to rack1a single mutant, which was substantiated by deregulation of ROS levels. RACK1A and FSD1 accumulated in cycloheximide-sensitive structural condensates in the cytoplasm that colocalized with the stress granule marker protein TSN in roots. However, RACK1A knock-out completely abolished salt-stress-dependent relocation of FSD1 to structural condensates, suggesting that RACK1A recruits FSD1 to these stress granules. Thus, this study uncovers an entirely novel mechanism for the regulation of RACK1/FSD1-dependent antioxidant defense in response to salt stress in Arabidopsis.

plant biology↗

bioRxiv2023

Systematic microRNA screening identifies miR-19b as regulator of temozolomide response through targeting PP2A serine-threonine phosphatase in glioblastoma

Despite the standard of care, glioblastoma IDH wildtype (GBM) inevitably recurs, underscoring the need to develop new treatment strategies. To address the role of microRNAs in temozolomide (TMZ) response, we performed functional microRNA screens and consistently identified miR-19b. Our study reveals a novel axis between miR-19b and PPP2R5E subunit of serine/threonine protein phosphatase PP2A and establishes a so far unappreciated contribution of miR-19b in TMZ resistance of GBM. Specifically, our results demonstrate that attenuation of miR-19b in GBM cell lines and glioblastoma stem cells (GSCs) induces DNA damage, which further enhances the cytotoxic effects of TMZ treatment. We confirmed TMZ resistance induced by knocking down PPP2R5E in orthotopic mouse xenografts of GSCs. Furthermore, our results indicate that treating cells with the PP2A-activating drug FTY720 or knocking down endogenous PP2A-inhibiting proteins potentiates the cytotoxic effects of TMZ. MiR-19b attenuation or PPP2R5E activation could potentially be exploited in adjuvant therapy of GBM patients.

cancer biology↗

bioRxiv2022

Genetic manipulation of stress-induced mitogen-activated protein kinase modulates early stages of the nodulation process in Medicago sativa

Leguminous plants have established a mutualistic endosymbiotic interaction with nitrogen-fixing rhizobia to secure nitrogen sources in new specialized organs called root nodules. Before nodule formation, the development of early symbiotic structures is essential for rhizobia docking, internalization, targeted delivery, and intracellular accommodation. We have recently reported that overexpression of stress-induced mitogen-activated protein kinase (SIMK) in alfalfa affects root hair, nodule and shoot formation. However, detailed subcellular spatial distribution, activation, and developmental relocation of SIMK during the early stages of alfalfa nodulation remain unclear. Here, we qualitatively and quantitatively characterized SIMK distribution patterns in rhizobium-infected root hairs using live-cell imaging and immunolocalization, employing alfalfa stable transgenic lines with genetically manipulated SIMK abundance and kinase activity. In the SIMKK-RNAi line, showing downregulation of SIMKK and SIMK, we found a considerably decreased accumulation of phosphorylated SIMK around infection pockets and infection threads, which was strongly increased in the GFP-SIMK line, constitutively overexpressing GFP-tagged SIMK. Thus, genetically manipulated SIMK modulates root hair capacity to form infection pockets and infection threads. These results shed new light on SIMK spatio-temporal participation in the early interactions between alfalfa and rhizobia, and its internalization into root hairs, showing that local accumulation of active SIMK indeed modulates nodulation in alfalfa. One sentence summaryGenetic manipulation of SIMK in alfalfa revealed that SIMK modulates root hair capacity to form infection pockets and infection threads during the early interactions between alfalfa and rhizobia.

plant biology↗