Cytokinin Perception in Ancient Plants beyond Angiospermae.
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ABSTRACT:
SUBMITTER: Lomin SN
PROVIDER: S-EPMC8657898 | biostudies-literature |
REPOSITORIES: biostudies-literature
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Project description:The phytohormone cytokinin is a key player in many developmental processes and in the response of plants to biotic and abiotic stress. The cytokinin signal is perceived and transduced via a multistep variant of the bacterial two-component signaling system. Most of the research on cytokinin signaling has been done in the model plant Arabidopsis thaliana. Research on cytokinin signaling has expanded to a much broader range of plants species in recent years. This is due to the natural limitation of Arabidopsis as a model species for the investigation of processes like nodulation or wood formation. The rapidly increasing number of sequenced plant genomes also facilitates the use of other species in this line of research. This review summarizes what is known about the cytokinin signaling in the different organisms and highlights differences to Arabidopsis.
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Project description:Plant hormone cytokinins are perceived by a subfamily of sensor histidine kinases (HKs), which via a two-component phosphorelay cascade activate transcriptional responses in the nucleus. Subcellular localization of the receptors proposed the endoplasmic reticulum (ER) membrane as a principal cytokinin perception site, while study of cytokinin transport pointed to the plasma membrane (PM)-mediated cytokinin signalling. Here, by detailed monitoring of subcellular localizations of the fluorescently labelled natural cytokinin probe and the receptor ARABIDOPSIS HISTIDINE KINASE 4 (CRE1/AHK4) fused to GFP reporter, we show that pools of the ER-located cytokinin receptors can enter the secretory pathway and reach the PM in cells of the root apical meristem, and the cell plate of dividing meristematic cells. Brefeldin A (BFA) experiments revealed vesicular recycling of the receptor and its accumulation in BFA compartments. We provide a revised view on cytokinin signalling and the possibility of multiple sites of perception at PM and ER.
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Project description:Potato is the most economically important non-cereal food crop. Tuber formation in potato is regulated by phytohormones, cytokinins (CKs) in particular. The present work studied CK signal perception in potato. The sequenced potato genome of doubled monoploid Phureja was used for bioinformatic analysis and as a tool for identification of putative CK receptors from autotetraploid potato cv. Désirée. All basic elements of multistep phosphorelay required for CK signal transduction were identified in the Phureja genome, including three genes orthologous to three CK receptor genes (AHK 2-4) of Arabidopsis. As distinct from Phureja, autotetraploid potato contains at least two allelic isoforms of each receptor type. Putative receptor genes from Désirée plants were cloned, sequenced and expressed, and the main characteristics of encoded proteins were determined, in particular their consensus motifs, modelled structure, ligand-binding properties, and ability to transmit CK signals. In all studied aspects the predicted sensor histidine kinases met the requirements for genuine CK receptors. Expression of potato CK receptors was found to be organ-specific and sensitive to growth conditions, particularly to sucrose content. Our results provide a solid basis for further in-depth study of CK signaling system and biotechnological improvement of potato.
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Project description:Plant growth and development are critically influenced by unpredictable abiotic factors. To survive fluctuating changes in their environments, plants have had to develop robust adaptive mechanisms. The dynamic and complementary actions of the auxin and cytokinin pathways regulate a plethora of developmental processes, and their ability to crosstalk makes them ideal candidates for mediating stress-adaptation responses. Other crucial signaling molecules responsible for the tremendous plasticity observed in plant morphology and in response to abiotic stress are reactive oxygen species (ROS). Proper temporal and spatial distribution of ROS and hormone gradients is crucial for plant survival in response to unfavorable environments. In this regard, the convergence of ROS with phytohormone pathways acts as an integrator of external and developmental signals into systemic responses organized to adapt plants to their environments. Auxin and cytokinin signaling pathways have been studied extensively. Nevertheless, we do not yet understand the impact on plant stress tolerance of the sophisticated crosstalk between the two hormones. Here, we review current knowledge on the function of auxin and cytokinin in redirecting growth induced by abiotic stress in order to deduce their potential points of crosstalk.
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Project description:BackgroundCytokinin Response Factors (CRFs) are a small subset of AP2/ERF transcription factor genes shown in Arabidopsis to regulate leaf development as part of the cytokinin signal transduction pathway. This study examines the phylogenetic distribution of CRF genes in other plant species, and attempts to identify the extent of sequence conservation and potential gene function among all CRF genes.ResultsWe identified CRF genes in representatives of all major land plant lineages, including numerous flowering plant taxa in addition to the model systems in which ERF genes have been catalogued. Comparative analysis across this broader sampling has identified strongly conserved amino acid motifs other than the AP2/ERF domain for all CRF proteins as well as signature sequences unique to specific clades of CRF genes. One of these motifs, here designated as the CRF domain, is conserved in and unique to CRF proteins distinguishing them from related genes. We show that this novel domain of approximately 65 amino acids is found in CRF proteins from all groups of land plants and only in CRF genes. Phylogenetic analyses suggest that the evolution of CRF genes has included numerous duplication events. In this phylogenetic context we examine protein evolution including the gain and loss of accessory domains, correlate these molecular evolutionary events with experimental data on cytokinin regulation and speculate on the function and evolution of the CRF domain within AP2/ERF transcription factor proteins. We also tested a prediction drawn from the phylogenetic analyses that four CRF domain containing genes from Tomato, previously unexamined for cytokinin response, are transcriptionally inducible by cytokinin, supporting the link between CRF genes, CRF-specific domains and cytokinin regulation.ConclusionCRF genes can be identified in all lineages of land plants, as a distinct subset of AP2/ERF proteins containing a specific and unique CRF domain. The CRF domain can be used to identify previously unclassified predicted genes or genes identified only as members of the AP2/ERF protein family. CRF domain presence and phylogenetic relatedness to known Arabidopsis CRF genes predicts gene function to some extent.
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Project description:The menopausal transition is marked by increased prevalence in disturbed sleep and insomnia, present in 40-60% of women, but evidence for a physiological basis for their sleep complaints is lacking. We aimed to quantify sleep disturbance and the underlying contribution of objective hot flashes in 72 women (age range: 43-57 years) who had (38 women), compared to those who had not (34 women), developed clinical insomnia in association with the menopausal transition. Sleep quality was assessed with two weeks of sleep diaries and one laboratory polysomnographic (PSG) recording. In multiple regression models controlling for menopausal transition stage, menstrual cycle phase, depression symptoms, and presence of objective hot flashes, a diagnosis of insomnia predicted PSG-measured total sleep time (p < 0.01), sleep efficiency (p = 0.01) and wakefulness after sleep onset (WASO) (p = 0.01). Women with insomnia had, on average, 43.5 min less PSG-measured sleep time (p < 0.001). There was little evidence of cortical EEG hyperarousal in insomniacs apart from elevated beta EEG power during REM sleep. Estradiol and follicle stimulating hormone levels were unrelated to beta EEG power but were associated with the frequency of hot flashes. Insomniacs were more likely to have physiological hot flashes, and the presence of hot flashes predicted the number of PSG-awakenings per hour of sleep (p = 0.03). From diaries, women with insomnia reported more WASO (p = 0.002), more night-to-night variability in WASO (p < 0.002) and more hot flashes (p = 0.012) compared with controls. Women who develop insomnia in the approach to menopause have a measurable sleep deficit, with almost 50% of the sample having less than 6h of sleep. Compromised sleep that develops in the context of the menopausal transition should be addressed, taking into account unique aspects of menopause like hot flashes, to avoid the known negative health consequences associated with insufficient sleep and insomnia in midlife women.
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Project description:Life arose in a world without oxygen and the first organisms were anaerobes. Here we investigate the gene repertoire of the prokaryote common ancestor, estimating which genes it contained and to which lineages of modern prokaryotes it was most similar in terms of gene content. Using a phylogenetic approach we found that among trees for all 8779 protein families shared between 134 archaea and 1847 bacterial genomes, only 1045 have sequences from at least two bacterial and two archaeal groups and retain the ancestral archaeal-bacterial split. Among those, the genes shared by anaerobes were identified as candidate genes for the prokaryote common ancestor, which lived in anaerobic environments. We find that these anaerobic prokaryote common ancestor genes are today most frequently distributed among methanogens and clostridia, strict anaerobes that live from low free energy changes near the thermodynamic limit of life. The anaerobic families encompass genes for bifunctional acetyl-CoA-synthase/CO-dehydrogenase, heterodisulfide reductase subunits C and A, ferredoxins, and several subunits of the Mrp-antiporter/hydrogenase family, in addition to numerous S-adenosyl methionine (SAM) dependent methyltransferases. The data indicate a major role for methyl groups in the metabolism of the prokaryote common ancestor. The data furthermore indicate that the prokaryote ancestor possessed a rotor stator ATP synthase, but lacked cytochromes and quinones as well as identifiable redox-dependent ion pumping complexes. The prokaryote ancestor did possess, however, an Mrp-type H(+)/Na(+) antiporter complex, capable of transducing geochemical pH gradients into biologically more stable Na(+)-gradients. The findings implicate a hydrothermal, autotrophic, and methyl-dependent origin of life. This article is part of a Special Issue entitled 'EBEC 2016: 19th European Bioenergetics Conference, Riva del Garda, Italy, July 2-6, 2016', edited by Prof. Paolo Bernardi.
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