Biology subjects

Trtilek, M.

Publications and source records attributed to Trtilek, M..

6 recordsLinked to original sources

bioRxiv2023

Shoot phenotyping of cytokinin receptors mutants revealed fluorescence parameters as early markers of drought stress

Plant phenotyping represents an increasing promise in plant research by providing a complex picture of plant development and fitness. In research focused on various environmental stresses, phenotyping can uncover markers that can sensitively assess the stress impact in very early stages before morphological changes. PlantScreenTM System represents a tool dedicated for shoot and root phenotyping in soil enabling high-precision, high-throughput phenotyping of small, mid-size and large plants. The system offers wide range of sensors providing the number of non-invasive analyses of morphological and physiological parameters as well as of pigments, water, or metabolite content. In our work, we combined phenotyping approaches to determine morphological changes and the status of the photosynthetic apparatus in Arabidopsis plants exposed to drought stress. Focused on morphology, the rosette area became smaller after seven days of drought stress when compared to control conditions. Interestingly, cytokinin signalling mutant ahk2 ahk3 revealed drought resistance compared to other genotypes. The fluorescent parameters showed higher sensitivity even in wild type. Non-photochemical quenching displayed values connected to reduced activity of photosynthetic apparatus after five days of drought stress. Taken together, acquired fluorescence parameters can serve as a marker of drought stress detection before morphological alterations occur. HighlightFluorescence parameters can serve as early markers of drought stress before morphological alterations appear. Shoot phenotyping of cytokinin receptor mutants showed drought resistance in the ahk2 ahk3 double mutant.

plant biology↗

bioRxiv2023

Primary multistep phosphorelay activation comprises both cytokinin and abiotic stress responses in Brassicaceae

Multistep phosphorelay (MSP) signaling integrates hormonal and environmental signals to control plant development and adaptive responses. The type-A RESPONSE REGULATORs (RRAs), the downstream members of the MSP cascade and cytokinin primary response genes, are supposed to mediate primarily the negative feedback regulation of (cytokinin-induced) MSP signaling. However, the transcriptional data suggest the involvement of RRAs in stress-related responses as well. By employing evolutionary conservation with the well-characterized Arabidopsis thaliana RRAs, we identified 5 and 38 novel putative RRAs in Brassica oleracea and Brassica napus, respectively. Our phylogenetic analysis suggests the existence of gene-specific selective pressure, maintaining the homologs of ARR3, ARR6, and ARR16 as singletons during the evolution of Brassica oleracea and Brassica rapa. We categorized RRAs based on the kinetics of their cytokinin-mediated upregulation and observed both similarities and specificities in this type of response across Brassicaceae. Using bioinformatic analysis and experimental data demonstrating the cytokinin responsiveness of Arabidopsis-derived TCSv2 reporter, we unveil the mechanistic conservation of cytokinin-mediated upregulation of RRAs in Brassica rapa and Brassica napus. Notably, we identify partial cytokinin dependency of cold stress-induced RRA transcription, thus corroborating the role of cytokinin signaling in the crop adaptive responses. HighlightsWe identified Brassica homologs of Arabidopsis type-A response regulators (RRAs), demonstrate existence of selective pressure preventing several RRAs multiplication during Brassicaceae evolution and describe cytokinin dependency of cold-induced RRAs upregulation.

plant biology↗

bioRxiv2021

Antenna modification leads to enhanced nitrogenase activity in a high light tolerant cyanobacterium

Biological nitrogen fixation is an energy intensive process that contributes significantly towards supporting life on this planet. Among nitrogen-fixing organisms, cyanobacteria remain unrivaled in their ability to fuel the energetically expensive nitrogenase reaction with photosynthetically harnessed solar energy. In heterocystous cyanobacteria light-driven, photosystem I (PSI)-mediated ATP synthesis plays a key role in propelling the nitrogenase reaction. Efficient light transfer to the photosystems rely on phycobilisomes (PBS), the major antenna protein complexes. PBS undergo degradation as a natural response to nitrogen starvation. Upon nitrogen availability, these proteins are resynthesized back to normal levels in vegetative cells, but their occurrence and function in heterocysts remains inconclusive. Anabaena 33047 is a heterocystous cyanobacterium that thrives under high light, harbors higher amounts of PBS in its heterocysts and fixes nitrogen at higher rates compared to other heterocystous cyanobacteria. To assess the relationship between PBS in heterocysts and nitrogenase function, we engineered a strain that retains high amounts of the antenna proteins in its heterocysts. Intriguingly, under high light intensities the engineered strain exhibited unusually high rates of nitrogenase activity compared to the wild type. Spectroscopic analysis revealed altered PSI kinetics in the mutant, with increased cyclic electron flow around PSI, a route that contributes to ATP generation and nitrogenase activity in heterocysts. Retaining higher levels of PBS in heterocysts appears to be an effective strategy to enhance nitrogenase function in cyanobacteria that are equipped with the machinery to operate under high light intensities. ImportanceThe function of phycobilisomes, the large antenna protein complexes in heterocysts has long been debated. This study provides direct evidence of the involvement of these proteins in supporting nitrogenase activity in Anabaena 33047, a heterocystous cyanobacterium that has affinity for very high light intensities. This strain was previously known to be recalcitrant to genetic manipulation and hence despite its many appealing traits, remained largely unexplored. We developed a genetic modification system for this strain and generated a {Delta}nblA mutant that exhibited resistance to phycobilisome degradation upon nitrogen starvation. Physiological characterization of the strain indicated that PBS degradation is not essential for acclimation to nitrogen deficiency and retention of PBS is advantageous for nitrogenase function.

microbiology↗

bioRxiv2021

AHK5 mediates ETR1-initiated multistep phosphorelay in Arabidopsis

Plants, like other sessile organisms, need to sense many different signals, and in response to them, modify their developmental programs to be able to survive in a highly changing environment. The multistep phosphorelay (MSP) in plants is a good candidate for a response mechanism that integrates multiple signal types both environmental and intrinsic in origin. Recently, ethylene was shown to control MSP activity via the histidine kinase (HK) activity of ETHYLENE RESPONSE 1 (ETR1)1,2, but the underlying molecular mechanism still remains unclear. Here we show that although ETR1 is an active HK, its receiver domain (ETR1RD) is structurally and functionally unable to accept the phosphate from the phosphorylated His in the ETR1 HK domain (ETR1HK) to initiate the phosphorelay to ARABIDOPSIS HISTIDINE-CONTAINING PHOSPHOTRANSMITTERs (AHPs), the next link downstream members in MSP signaling. Instead, ETR1 interacts with another HK ARABIDOPSIS HISTIDINE KINASE 5 (AHK5) and transfers the phosphate from ETR1HK through the receiver domain of AHK5 (AHK5RD), and subsequently to AHP1, AHP2 and AHP3, independently of the HK activity of AHK5. We show that AHK5 is necessary for ethylene-initiated, but not cytokinin-initiated, MSP signaling in planta and that it thus mediates hormonal control of root growth.

plant biology↗

bioRxiv2020

Genetic mapping of the early responses to salt stress in Arabidopsis thaliana

Salt stress decreases plant growth prior to significant ion accumulation in the shoot. However, the processes underlying this rapid reduction in growth are still unknown. To understand the changes in salt stress responses through time and at multiple physiological levels, examining different plant processes within a single setup is required. Recent advances in phenotyping has allowed the image-based estimation of plant growth, morphology, colour and photosynthetic activity. In this study, we examined the salt stress-induced responses of 191 Arabidopsis accessions from one hour to seven days after treatment using high-throughput phenotyping. Multivariate analyses and machine learning algorithms identified that quantum yield measured in the light-adapted state (Fv'/Fm') greatly affected growth maintenance in the early phase of salt stress, while maximum quantum yield (QY max) was crucial at a later stage. In addition, our genome-wide association study (GWAS) identified 770 loci that were specific to salt stress, in which two loci associated with QY max and Fv'/Fm' were selected for validation using T-DNA insertion lines. We characterised an unknown protein kinase found in the QY max locus, which reduced photosynthetic efficiency and growth maintenance under salt stress. Understanding the molecular context of the identified candidate genes will provide valuable insights into the early plant responses to salt stress. Furthermore, our work incorporates high-throughput phenotyping, multivariate analyses and GWAS, uncovering details of temporal stress responses, while identifying associations across different traits and time points, which likely constitute the genetic components of salinity tolerance.

plant biology↗

bioRxiv2019

Increased expression of mitochondrial dysfunction stimulon genes affects chloroplast redox status and photosynthetic electron transfer in Arabidopsis

Mitochondrial retrograde signals control expression of nuclear mitochondrial dysfunction stimulon (MDS) genes. Although MDS gene products mostly affect mitochondrial functions, they also influence production of reactive oxygen species (ROS) and redox status of chloroplasts. To study this inter-organellar interaction, we analysed the response of the Arabidopsis MDS-overexpressor mutant rcd1 to methyl viologen (MV), which catalyses electron transfer from Photosystem I (PSI) to molecular oxygen, generating ROS in Mehlers reaction. The response of plants to MV was investigated by imaging chlorophyll fluorescence in aerobic and hypoxic environments, and by membrane inlet mass spectrometry. Hypoxic treatment abolished the effect of MV on photosynthetic electron transfer in rcd1, but not in wild type. A similar reaction to hypoxia was observed in other MDS-activating lines and treatments. This suggests that MDS gene products contribute to oxygen depletion at the PSI electron-acceptor side. In unstressed growth conditions this MDS-related effect is likely masked by endogenous oxygen evolution and gas exchange with the atmosphere. In rcd1, altered Mehlers reaction coincided with more reduced state of the chloroplast NADPH-thioredoxin oxidoreductase C (NTRC) and its targets, suggesting that NTRC performs feedback control of photosynthesis. This regulation may represent a novel mechanism whereby mitochondrial retrograde signalling affects chloroplast functions.

plant biology↗