Ondrej Novak

Palacký University Olomouc · Laboratory of Growth Regulators

Cytokinins (CKs) play a crucial role in many physiological and developmental processes at the levels of individual plant components (cells, tissues, and organs) and by coordinating activities across these parts. High-resolution measurements of intracellular CKs in different plant tissues can therefore provide insights into their metabolism and mode...

Coordination of cell division and pattern formation is central to tissue and organ development, particularly in plants where walls prevent cell migration. Auxin and cytokinin are both critical for division and patterning, but it is unknown how these hormones converge upon tissue development. We identify a genetic network that reinforces an early em...

Cytokinins are a major group of phytohormones regulating plant growth, development and stress responses. However, in contrast to the well-defined polar transport of auxins, the molecular basis of cytokinin transport is poorly understood. Here we show that an ATP-binding cassette transporter in Arabidopsis, AtABCG14, is essential for the acropetal (...

The plant hormone auxin is believed to influence almost every aspect of plant growth and development. Auxin transport, biosynthesis and degradation combine to form gradients of the hormone that influence a range of key developmental and environmental response processes. There is abundant genetic evidence for the existence of multiple pathways for a...

Adenosine undergoes ATP-dependent phosphorylation catalyzed by adenosine kinase (ADK). In plants, ADK also phosphorylates cytokinin ribosides, transport forms of the hormone. Here, we investigated the substrate preferences, oligomeric states and structures of ADKs from moss (Physcomitrella patens) and maize (Zea mays) alongside metabolomic and phen...

Plant reactions to stress vary with development stage and fitness. This study assessed the relationship between light and chilling stress in Arabidopsis acclimation. By analyzing the transcriptome and proteome responses of expanding leaves subjected to varying light intensity and cold, 2251 and 2064 early response genes and proteins were identified...

Temperatures above the optimum growth temperature affect seed development, producing seeds with ruptured seed coats. This phenotype is associated with accelerated embryo development. However, the molecular mechanism underlying this effect remains unclear. To investigate the occurrence of temperature-induced seed coat rupture, we combined detailed p...

Jasmonates (JAs) are a family of oxylipin phytohormones regulating plant development and growth and mediating ‘defense versus growth’ responses. The upstream JA biosynthetic precursor cis-(+)-12-oxo-phytodienoic acid (cis-OPDA) acts independently of CORONATIVE INSENSITIVE 1 (COI1)-mediated JA signaling in several stress-induced and developmental pr...

In recent years, substantial progress has been made in exploring auxin conjugation and metabolism, primarily aiming at indole-3-acetic acid (IAA). However, the metabolic regulation of another key auxin, phenylacetic acid (PAA), remains largely uncharacterized. Here, we provide a comprehensive exploration of PAA metabolism in land plants. Through LC...

Hormone perception and signaling pathways play a fundamental regulatory function in the physiological processes of plants. Cytokinins, plant hormones, regulate cell division and meristem maintenance. The cytokinin signaling pathway is well-established in model plant Arabidopsis. Several negative feedback mechanisms, tightly controlling the cytokini...

Seed-to-seedling transition represents a key developmental and metabolic switch in plants. Catabolism of seed storage reserves fuels germination and early seedling emergence until photosynthesis is established. The developmental transition is controlled by Polycomb repressive complex 2 (PRC2). However, the coordination of PRC2 activity and its cont...

Tetranychus urticae is an important pest that causes severe damage to a wide variety of plants and crops, leading to a substantial productivity loss. Previous research has been focused on plant defence response to T. urticae to improve plant resistance. However, plant growth, development and reproduction throughout the infestation process have not...

Abscisic acid (ABA) is a phytohormone that occurs in plants at very low concentration (pmol/g fresh weight) and regulates multiple biological processes, including stomatal closure, seed germination, and responses to environmental stresses. In the present study, isolation of ABA, ABA glucosyl ester, and 11 ABA amino acid conjugates from minute quant...

Root hairs (RH) as mixed tip- and non-tip growing protrusions that develop from root epidermal cells are important for nutrient, and water uptake as well as for root anchoring and interaction with soil microorganisms. Although nutrient availability and temperature are key interlinked factors for a sustained plant growth, the molecular mechanisms un...

Smoke-water (SW) and Karrikinolide1 (KAR1) release dormancy and improve seed germination in many plant species. Therefore, we tested SW (1:2500 v/v) and KAR1 (10−7 M) to break the morphological dormancy of celery cultivar (Apium graveolens L.). In the first trial, seeds were subjected to a 21-day incubation period at 20 °C with SW and KAR1 applied...

Potato, the most important non-cereal crop, is highly water and space efficient but susceptible to abiotic stress such as heat, drought, or flooding. Climate change is severely increasing the likelihood of such stresses to occur individually, sequentially, or simultaneously. However, the understanding of acclimation to abiotic stress in crops in ge...

Formation of the apical hook in etiolated dicot seedlings results from differential growth in the hypocotyl apex and is tightly controlled by environmental cues and hormones, among which auxin and gibberellins (GAs) play an important role. Cell expansion is tightly regulated by the cell wall, but whether and how feedback from this structure contrib...

Due to technological advances in mass spectrometry, significant progress has been achieved recently in plant hormone research. Nowadays, plant hormonomics is well established as a fully integrated scientific field focused on the analysis of phytohormones, mainly on their isolation, identification and spatiotemporal quantification in plants. This re...

Callus formation and shoot regeneration are natural plant abilities triggered by stress and damage. They are also key components of tissue culture, which for many species is crucial for gene editing, transformation, propagation, and other technologies, and their study provides valuable insights into plant development. The transcription factor ENHAN...

In epiphytes, aerial roots are important to combat water‐deficient, nutrient‐poor, and high‐irradiance microhabitats. However, whether aerial roots can respond to gravity and whether auxin plays a role in regulating aerial root development remain open‐ended questions. Here, we investigated the gravitropic response of the epiphytic orchid Phalaenops...

The complex processes of pollen germination and pollen tube elongation are important events in the sexual reproduction of flowering plants and are essential to the success of seed formation. However, unfavourable environmental and climatic conditions affect pollen performance negatively. Integrating the application of various biostimulants represen...

Although microalgae have only recently been recognized as part of the plant and soil microbiome, their application as biofertilizers has a tradition in sustainable crop production. Under consideration of their ability to produce the plant growth‐stimulating hormone cytokinin (CK), known to also induce pathogen resistance, we have assessed the bioco...

Neuroactive steroids are a group of steroid molecules that are involved in the regulation of functions of the nervous system. The nervous system is not only the site of their action, but their biosynthesis can also occur there. Neuroactive steroid levels depend not only on the physiological state of an individual (person's sex, age, diurnal variati...

Plants in habitats with unpredictable conditions often have diversified bet-hedging strategies that ensure fitness over a wider range of variable environmental factors. A striking example is the diaspore (seed and fruit) heteromorphism that evolved to maximize species survival in Aethionema arabicum (Brassicaceae) in which external and endogenous t...

Background Gaseous phytohormone ethylene levels are directly influenced by the production of its immediate non-volatile precursor 1-aminocyclopropane-1-carboxylic acid (ACC). Owing to the strongly acidic character of the ACC molecule, its quantification has been difficult to perform. Here, we present a simple and straightforward validated method fo...

Apical hook development is an ideal model for studying differential growth in plants, and is controlled by complex hormonal crosstalk, with auxin and ethylene being the major players. Here, we identified a bioactive small molecule that decelerates apical hook opening in Arabidopsis thaliana . Our genetic studies suggest that this molecule enhances...

Smoke–water, a smoke-saturated solution derived from the smoke generated by burning plant materials, promotes seed germination and growth of various plant species. There are many reported studies where seeds are treated and soils are drenched with smoke–water to explore the beneficial effects of smoke. However, little information is available on th...

The shoot of green plants is the primary site of carbon assimilation into sugars, the key source of energy and metabolic building blocks. The systemic transport of sugars is essential for plant growth and morphogenesis. Plants evolved intricate networks of molecular players to effectively orchestrate the subcellular partitioning of sugars. Dynamic...

Seasonal dynamics of root growth play an important role in large‐scale ecosystem processes; they are largely governed by growth regulatory compounds and influenced by environmental conditions. Yet, our knowledge about physiological drivers of root growth is mostly limited to laboratory‐based studies on model plant species. We sampled root tips of E...

Although the pesticide hexachlorocyclohexane (HCH) and its isomers have long been banned, their presence in the environment is still reported worldwide. In this study, we investigated the bioaccumulation potential of α, β, and δ hexachlorocyclohexane (HCH) isomers in black alder saplings (Alnus glutinosa) to assess their environmental impact. Each...

Some pathological conditions affecting the human body can also disrupt metabolic pathways and thus alter the overall metabolic profile. Knowledge of metabolic disturbances in specific diseases could thus enable the differential diagnosis of otherwise similar conditions. This work therefore aimed to comprehensively characterize changes in tryptophan...

Background: Gaseous phytohormone ethylene levels are directly influenced by the production of its immediate non-volatile precursor 1-aminocyclopropane-1-carboxylic acid (ACC). Owing to the strongly acidic character of the ACC molecule, its quantification has been difficult to perform. Here, we present a simple and straightforward validated method f...

Auxin amino acid conjugates are considered to be storage forms of auxins. Previous research has shown that indole-3-acetyl-L-alanine (IAA-Ala), indole-3-propionyl-L-alanine (IPA-Ala) and indole-3-butyryl-L-alanine (IBA-Ala) affect the root growth of Brassica rapa seedlings. To elucidate the potential mechanism of action of the conjugates, we treate...

Photosynthesis is among the first processes negatively affected by environmental cues and its performance directly determines plant cell fitness and ultimately crop yield. Primarily sites of photosynthesis, chloroplasts are unique sites also for the biosynthesis of precursors of the growth regulator auxin and for sensing environmental stress, but t...

Introduction Cytokinins, a group of adenine derivatives, are phytohormones that regulate many aspects of the plant's reaction to changes in the abiotic and biotic environment and ensure the correct execution of developmental programs. While the signaling pathway and its effects are very well established for Angiosperms, its origin, and evolution ar...

Plants in habitats with unpredictable conditions are often characterized by diversifying their bet-hedging strategies that ensure fitness over a wider range of variable environmental factors. A striking example is the diaspore (seed and fruit) heteromorphism that evolved to maximize species survival in Aethionema arabicum (Brassicaceae) in which ex...

Cells save their energy during nitrogen starvation by selective autophagy of ribosomes and degradation of RNA to ribonucleotides and nucleosides. Nucleosides are hydrolyzed by nucleoside N‐ribohydrolases (nucleosidases, NRHs). Subclass I of NRHs preferentially hydrolyzes the purine ribosides while subclass II is more active towards uridine and xant...

Due to their long lifespan, trees and bushes develop higher order of branches in a perennial manner. In contrast to a tall tree, with a clearly defined main stem and branching order, a bush is shorter and has a less apparent main stem and branching pattern. To address the developmental basis of these two forms, we studied several naturally occurrin...

Waterlogging leads to hypoxic conditions in the root zone that subsequently cause systemic adaptive responses in the shoot, including leaf epinasty. Waterlogging-induced epinasty in tomato has long been ascribed to the coordinated action of ethylene and auxins. However, other hormonal signals have largely been neglected, despite evidence of their i...

In situ separation and visualization of synthetic and naturally occurring isomers from heterogeneous plant tissues, especially when they share similar molecular structures, are a challenging task. In this study, we combined the ion mobility separation with desorption electrospray ionization mass spectrometry imaging (DESI-IM-MSI) to achieve a direc...

Auxin belongs among major phytohormones and governs multiple aspects of plant growth and development. The establishment of auxin concentration gradients, determines, among other processes, plant organ positioning and growth responses to environmental stimuli. Herein we report the synthesis of new NBD- or DNS-labelled IAA derivatives and the elucida...

Background Drought is a major environmental stress that affects crop productivity worldwide. Although previous research demonstrated links between strigolactones (SLs) and drought, here we used barley (Hordeum vulgare) SL-insensitive mutant hvd14 (dwarf14) to scrutinize the SL-dependent mechanisms associated with water deficit response. Results We...

Tree growth and survival are dependent on their ability to perceive signals, integrate them, and trigger timely and fitted molecular and growth responses. While ectomycorrhizal symbiosis is a predominant tree‐microbe interaction in forest ecosystems, little is known about how and to what extent it helps trees cope with environmental changes. We hyp...

N6-methyl adenosine (m6A) is a widespread internal mRNA modification impacting the expression of numerous genes. Here we characterize the auxin-related defects among the pleiotropic phenotypes of the hypomorphic Arabidopsis thaliana mutants with the impaired status of m6A and present that they show strong resistance to exogenously applied auxin. By...

Auxins and cytokinins are two major families of phytohormones that control most aspects of plant growth, development and plasticity. Their distribution in plants has been described, but the importance of cell- and subcellular-type specific phytohormone homeostasis remains undefined. Herein, we revealed auxin and cytokinin distribution maps showing...

Neurodegenerative diseases are a broad heterogeneous group affecting the nervous system. They are characterized, from a pathophysiological perspective, by the selective involvement of a subpopulation of nerve cells with a consequent clinical picture of a disease. Clinical diagnoses of neurodegenerative diseases are quite challenging and often not c...

Cis-(+)-12-oxophytodienoic acid (cis-(+)-OPDA) is a bioactive jasmonate, a precursor of jasmonic acid, which also displays signaling activity on its own. Modulation of cis-(+)-OPDA actions may be carried out via biotransformation leading to metabolites of various functions. This work introduces a methodology for the synthesis of racemic cis-OPDA co...

Introduction Chloroplast calcium homeostasis plays an important role in modulating the response of plants to abiotic and biotic stresses. One of the greatest challenges is to understand how chloroplast calcium-permeable pathways and sensors are regulated in a concerted manner to translate specific information into a calcium signature and to elucida...

Etiolated seedlings of dicots form an apical hook to protect the meristems during soil emergence. Hook formation is the result of differential growth on both sides of the hypocotyl apex and is tightly controlled by environmental cues and hormones, among which auxin and gibberellins (GAs) are the main contributors. Cell expansion is tightly regulate...

Spatiotemporal control over developmental programs is vital to all organisms. Here we show that cytokinin (signaling) deficiency leads to early secondary cell wall (SCW) formation in Arabidopsis inflorescence stem that associates with precocious upregulation of a SCW transcriptional cascade controlled by NAC TFs (NSTs). We demonstrate that cytokini...

Jasmonates (JAs) are a family of oxylipin phytohormones regulating plant development and growth and mediating "defense versus growth" responses. The upstream JA biosynthetic precursor cis-(+)-12-oxo-phytodienoic acid (cis-OPDA) has been reported to act independently of the COI1-mediated JA signaling in several stress-induced and developmental proce...

Deciduous trees exhibit a spectacular phenomenon of autumn senescence driven by the seasonality of their growth environment, yet there is no consensus which external or internal cues trigger it. Senescence starts at different times in European aspen (Populus tremula L.) genotypes grown in same location. By integrating omics studies, we demonstrate...

Auxins are a group of phytohormones that play a key role in plant growth and development, mainly presented by the major member of the family - indole-3-acetic acid (IAA). The levels of free IAA are regulated, in addition to de novo biosynthesis, by irreversible oxidative catabolism and reversible conjugation with sugars and amino acids. These conju...

Cis-(+)-12-oxophytodienoic acid (cis-(+)-OPDA) is a bioactive jasmonate, a precursor of jasmonic acid, which also displays signaling activity on its own. Modulation of cis-(+)-OPDA actions may be carried out via biotransformation leading to metabolites of various functions, similar to other phytohormones. This work introduces a methodology for the...

Auxins play an important role in plant physiology and are involved in numerous aspects of plant development, such as cell division, elongation and differentiation, fruit development, and phototropic response. In addition, through their antagonistic interaction with cytokinins, auxins play a key role in the regulation of root growth and apical domin...

Chemical inhibitors are often implemented for the functional characterization of genes to overcome the limitations associated with genetic approaches. Although it is well established that the specificity of the compound is key to success of a pharmacological approach, off-target effects are often overlooked or simply neglected in a complex biologic...

An environmentally responsive root system is crucial for plant growth and crop yield, especially in suboptimal soil conditions. This responsiveness enables the plant to exploit regions of high nutrient density while simultaneously minimizing abiotic stress. Despite the vital importance of root systems in regulating plant growth, significant gaps of...

C-TERMINALLY ENCODED PEPTIDE (CEP) and cytokinin hormones act over short and long distances to control plant responses to environmental cues. CEP and cytokinin pathway mutants share phenotypes, however, it is not known if these pathways intersect. We show that CEP and cytokinin signalling converge on CEP DOWNSTREAM (CEPD) glutaredoxins to inhibit p...