Biology subjects

Lacek, J.

Publications and source records attributed to Lacek, J..

7 recordsLinked to original sources

bioRxiv2026

Decarboxylation of indoleacetic acid illuminates its evolution into a plant hormone

The evolution of indoleacetic acid (IAA) into the plant hormone auxin remains unclear. Here, we compared IAA response and metabolism in land plants and their closest living relatives, the streptophyte algae, using chemical treatments, phytohormone profiling, and targeted and untargeted metabolomics. Streptophyte algae showed neither plant-like auxin responses nor canonical IAA metabolism. Here, we demonstrate IAA side-chain decarboxylation as a novel pathway of cellular IAA metabolism, operating in streptophyte algae and land plants alike. Decarboxylation also underpinned IAA's innate photolability and yielded cytotoxic intermediates, which also accumulated endogenously under simulated sunlight. Together, these findings establish IAA decarboxylation as a major, conserved metabolic pathway, and suggest that the metabolic constraints arising from IAA's instability and indirect cytotoxicity contributed to its adoption as a plant hormone.

plant biology↗

bioRxiv2025

The CATION CALCIUM EXCHANGER 4 (CCX4) regulates LRX1-related root hair development through Ca2+ homeostasis

Calcium, as a cellular second messenger, is essential for plant growth. A tip-focused Ca2+ gradient in polarized cells is considered to drive cell expansion. The cell wall polysaccharide pectin is a major Ca2+ binding structure and Ca2+ homeostasis is influenced by the cell wall architecture. LRR-extensin (LRX) proteins are extracellular regulators of cell wall development that are anchored in the cell wall by their extensin domain. The extensin-less LRX1{Delta}E14 variant of the root hair-expressed LRX1 of Arabidopsis induces a dominant-negative effect resulting in aberrant root hairs. In an effort to identify the underlying mechanism of the root hair defect caused by LRX1{Delta}E14, we isolated a suppressor of dominant-negative effect mutant, sune42. It codes for the CATION CALCIUM EXCHANGER 4 (CCX4) that localizes to the Golgi apparatus and was shown to have Ca2+ transport activity. A detailed investigation of the Ca2+ dynamics revealed that LRX1{Delta}E14 coincides with a defect in tip-focused cytoplasmic Ca2+ oscillation, and this effect is alleviated by the sune42 mutation. Additionally, reducing Ca2+ availability influences the LRX1{Delta}E14-induced root hair defect. We conclude that sune42 suppresses the root hair defect in LRX1{Delta}E14 through modulating cytoplasmic Ca2+ dynamics, pointing at the importance of the Golgi apparatus for cellular Ca2+ homeostasis.

plant biology↗

bioRxiv2025

SnRK1.1 Coordinates Organ-Specific Growth-Defense Programs via Transcriptomic Rewiring in Arabidopsis thaliana

SnRK1 (Sucrose non-fermenting-1-Related Kinase 1) is a master regulator of cellular energy homeostasis in plants, coordinating developmental and metabolic responses under environmental and internal stress conditions. Here, we demonstrate that its catalytic subunit, KIN10, orchestrates organ-specific growth-defense programs in Arabidopsis thaliana through transcriptomic rewiring. Using RNA-seq profiling, we reveal that kin10 knockout mutants exhibit extensive transcriptional reprogramming in roots, particularly in pathways linked to signal perception, cell wall remodeling, and intracellular trafficking, which correlates with impaired root growth and reduced root hair elongation upon Pseudomonas syringae infection. In contrast, KIN10 overexpression (KIN10-OE) lines display constitutive defense activation in shoots, including elevated expression of genes associated with reactive oxygen species (ROS) production and salicylic acid (SA) signaling, leading to enhanced ROS accumulation and growth trade-offs. kin10 roots show muted responses to biotic stimuli, while KIN10-OE shoots prioritize defense over growth. These findings position KIN10 as a critical integrator of energy status and immune signaling, enabling fine-tuned, tissue-specific responses essential for optimizing plant adaptation to dynamic environmental challenges.

plant biology↗

bioRxiv2025

Analysing the Role of KIN10 in Directional Root Growth Regulation in Arabidopsis thaliana

Root growth directionality is critical for plant survival, optimizing anchorage and resource acquisition. While the role of hormonal signaling in root gravitropism is well established, the contribution of metabolic status remains less understood. Here, we investigate the function of the catalytic SnRK1 subunit KIN10 in integrating carbon availability with root growth regulation in Arabidopsis thaliana. A combination of growth phenotyping, transcriptomics, and hormonomic profiling suggest that KIN10 loss disrupts energy-linked developmental processes. Compared to wild-type Col-0, kin10 displayed reduced sensitivity to glucose-induced root growth inhibition. Transcriptomic analysis of kin10 roots revealed widespread reprogramming of metabolic and hormonal pathways, with significant changes in secondary metabolism, cell wall remodeling, and hormone-related gene expression. Hormone profiling further indicated that KIN10 modulates auxin and jasmonate pathways in a carbon source- and organ-dependent manner, especially under sucrose supplementation. Our results demonstrate that KIN10 plays a central role in integrating energy status with developmental and environmental signaling.

plant biology↗

bioRxiv2024

Comprehensive Model of Cell-to-Cell Cytokinin Transport Reveals A Specific Mode of Cytokinin Riboside Influx

1Ribosylated forms of plant hormones cytokinins (CKs) are the dominant CK species translocated at long distances. Their particular roles in plant physiology imply the existence of a yet uncharacterized CK riboside-specific membrane transport system. In this work, we report significant differences in the kinetics of the membrane transport of CK nucleobases and ribosides and the overall affinity of membrane-bound carriers towards the two CK forms. We show that CK ribosides can inhibit the uptake of CK nucleobases in tobacco Bright Yellow 2 cell suspensions but not vice versa, confirming the existence of a membrane transport system that strictly recognizes CK ribosides. We further characterize the membrane transport of CK nucleobases and ribosides mediated by AtENT3 (EQULIBRATIVE NUCLEOSIDE TRANSPORTER 3), showing its preference towards trans-zeatin riboside (tZR) over isopentenyl adenosine (iPR). With the molecular docking and molecular dynamics, we assess the interactions among the side chain of tZR and AtENT3 residues Tyr61 and Asp129, which are conserved in all AtENTs but not in the ENTs from non-plant species. Lastly, we show that atent3 mutation affects shoot phenotype, demonstrating the impact of CK riboside membrane transport on shoot development.

plant biology↗

bioRxiv2023

Study of auxin metabolism using stable isotope labeling and LCMS; evidence for in planta auxin decarboxylation pathway.

The natural plant hormone auxin indole-3-acetic acid (IAA) influences many physiological processes in plants. Here, the metabolism of IAA was studied in detail using tobacco BY-2 cells as a model and compared with the in planta metabolism in several plant species. A combination of labeled/unlabeled substrate feeding, global untargeted mass spectrometric (MS) scanning, and selective MS filtering allowed the detection of 17 auxin metabolites, 15 of which were identified. Subsequent study of intermediate metabolism and dynamics revealed eight major pathways: three amino acid conjugation pathways with aspartate, glutamate, and glutamine, followed by their 2-oxidation with the help of the DAO enzyme; side-chain glucosyl ester formation; direct 2-oxidation; two decarboxylation pathways; and a pathway producing an unidentified metabolite. Interestingly, the first intermediates of the two decarboxylation pathways, indole-3-carbinol and oxoindole-3-carbinol, were formed outside the cells. We found that the majority of the detected auxin metabolites occur naturally in several plant species and that IAA is their precursor, indicating that the auxin metabolic pathways observed in BY-2 cells also occur in planta. Our finding that the IAA decarboxylation pathway occurs in planta, and the previous reports of auxin activity of some metabolites of this pathway, suggest that at least some of the biological effects of IAA may be explained by its conversion to decarboxylative metabolites.

plant biology↗

bioRxiv2022

RaPiD-chamber: Easy to self-assemble live-imaging chamber with adjustable LEDs allows to track small differences in dynamic plant movement adaptation on tissue level

Plants rely on fine-tuning organ movement to ensure their survival and productivity. Even subtle loss of directional growth orchestration can result in a huge impact when the plant is impaired to adapt to an ever-changing environment, where it is exposed to manifold exogenous stimuli simultaneously. We present a newly designed chamber to obtain live images to track organ growth and movement differences, called RaspberyPi Dark Chambers (RaPiD-chamber). The RaPiD-chamber is easy to self-assemble and cost-efficient and allows to monitor the continuous growth of etiolated seedlings, as well as their response to light of different wavelengths and from chosen positions. We tested the advice by comparing hypocotyl elongation rate and response to unilateral white and blue light exposure of Arabidopsis thaliana Col0. Additionally, we compared the elongation rate of etiolated hypocotyls between Col0 and kin10, a mutant lacking the catalytic subunit of the cellular signaling hub SUCROSE NON-FERMENTING RELATED KINASE 1 (SnRK1). kin10 is known for its diminished ability to control hypocotyl elongation. As a case study, we compared the growth dynamics of etiolated Col0 versus kin10. Without further energy source supplementation to the growth medium, the mutant cannot keep up with hypocotyl elongation. Additionally, continuous observation of the dark-grown seedlings allowed us to determine a shift in the dynamics of apical hook angle formation for the mutant.

plant biology↗