Light is one of the most important factor influencing plant growth and development all through their life cycle. One of the well-known light-regulated processes is de-etiolation, i.e. the switch from skotomorphogenesis to photomorphogenesis. The hormones cytokinins (CKs) play an important role during the establishment of photomorphogenesis as exogenous CKs induced photomorphogenesis of dark-grown seedlings. Most of the studies are conducted on the plant model Arabidopsis, but no or few information are available for important crop species, such as tomato (Solanum lycopersicum L.). In our study, we analyzed for the first time the endogenous CKs content in tomato hypocotyls during skotomorphogenesis, photomorphogenesis and de-etiolation. For this purpose, two tomato genotypes were used: cv. Rutgers (wild-type; WT) and its corresponding mutant (7B-1) affected in its responses to blue light (BL). Using physiological and molecular approaches, we identified that the skotomorphogenesis is characterized by an endoreduplication-mediated cell expansion, which is inhibited upon BL exposure as seen by the accumulation of trancripts encoding CycD3, key regulators of the cell cycle. Our study showed for the first time that iP (isopentenyladenine) is the CK accumulated in the tomato hypocotyl upon BL exposure, suggesting its specific role in photomorphogenesis. This result was supported by physiological experiments and gene expression data. We propose a common model to explain the role and the relationship between CKs, namely iP, and endoreduplication during de-etiolation and photomorphogenesis.

• MeSH
• buněčný cyklus účinky léků   genetika   MeSH
• cyklin D3 genetika   metabolismus   MeSH
• cytokininy metabolismus   MeSH
• endoreduplikace fyziologie   účinky záření   MeSH
• fylogeneze MeSH
• hypokotyl fyziologie   účinky záření   MeSH
• isopentenyladenosin metabolismus   MeSH
• morfogeneze fyziologie   účinky záření   MeSH
• ploidie MeSH
• rostlinné proteiny genetika   metabolismus   MeSH
• semenáček fyziologie   účinky záření   MeSH
• Solanum lycopersicum fyziologie   účinky záření   MeSH
• světlo MeSH
• Publikační typ
• časopisecké články MeSH
• práce podpořená grantem MeSH

Dark-induced growth (skotomorphogenesis) is primarily characterized by rapid elongation of the hypocotyl. We have studied the role of abscisic acid (ABA) during the development of young tomato (Solanum lycopersicum L.) seedlings. We observed that ABA deficiency caused a reduction in hypocotyl growth at the level of cell elongation and that the growth in ABA-deficient plants could be improved by treatment with exogenous ABA, through which the plants show a concentration dependent response. In addition, ABA accumulated in dark-grown tomato seedlings that grew rapidly, whereas seedlings grown under blue light exhibited low growth rates and accumulated less ABA. We demonstrated that ABA promotes DNA endoreduplication by enhancing the expression of the genes encoding inhibitors of cyclin-dependent kinases SlKRP1 and SlKRP3 and by reducing cytokinin levels. These data were supported by the expression analysis of the genes which encode enzymes involved in ABA and CK metabolism. Our results show that ABA is essential for the process of hypocotyl elongation and that appropriate control of the endogenous level of ABA is required in order to drive the growth of etiolated seedlings.

• MeSH
• cyklin-dependentní kinasy antagonisté a inhibitory   MeSH
• cytokininy biosyntéza   metabolismus   MeSH
• endoreduplikace účinky záření   MeSH
• homeostáza účinky záření   MeSH
• hypokotyl cytologie   růst a vývoj   metabolismus   účinky záření   MeSH
• inhibitory proteinkinas farmakologie   MeSH
• klíčení účinky léků   účinky záření   MeSH
• kyselina abscisová metabolismus   MeSH
• Solanum lycopersicum cytologie   růst a vývoj   metabolismus   účinky záření   MeSH
• tma * MeSH
• vývoj rostlin účinky léků   účinky záření   MeSH
• Publikační typ
• časopisecké články MeSH
• práce podpořená grantem MeSH

• The conserved family of Aurora kinases has multiple functions during mitosis. The roles of plant Aurora kinases have been characterized using inhibitor treatments. • We down-regulated Aurora kinases in Arabidopsis thaliana using RNA interference (RNAi). We carried out a detailed phenotypic analysis of Aurora RNAi plants, biochemical and microscopic studies of AtAurora1 kinase together with AtTPX2 (targeting protein for Xklp2) and γ-tubulin. • Cell division defects were observed in plants with reduced expression of Aurora kinases. Furthermore, the maintenance of primary meristems was compromised and RNAi seedlings entered endoreduplication prematurely. AtAurora1, its activator AtTPX2, and γ-tubulin were associated with microtubules in vitro; they were attached to regrowing kinetochore microtubules and colocalized on spindle microtubules and with a subset of early phragmoplast microtubules. Only the AtAurora1 kinase was translocated to the area of the cell plate. • RNAi silencing of Aurora kinases showed that, in addition to their function in regulating mitosis, the kinases are required for maintaining meristematic activity and controlling the switch from meristematic cell proliferation to differentiation and endoreduplication. The colocalization and co-fractionation of AtAurora1 with AtTPX2, and γ-tubulin on microtubules in a cell cycle-specific manner suggests that AtAurora1 kinase may function to phosphorylate substrates that are critical to the spatiotemporal regulation of acentrosomal microtubule formation and organization.

• MeSH
• Arabidopsis enzymologie   genetika   MeSH
• buněčné dělení MeSH
• down regulace MeSH
• duplikace genu genetika   MeSH
• fenotyp MeSH
• meristém enzymologie   genetika   růst a vývoj   MeSH
• mikrotubuly metabolismus   MeSH
• protein-serin-threoninkinasy metabolismus   MeSH
• proteiny asociované s mikrotubuly metabolismus   MeSH
• proteiny huseníčku metabolismus   MeSH
• RNA interference MeSH
• transport proteinů MeSH
• tubulin metabolismus   MeSH
• Publikační typ
• časopisecké články MeSH
• práce podpořená grantem MeSH

In many plant species, somatic cell differentiation is accompanied by endoreduplication, a process during which cells undergo one or more rounds of DNA replication cycles in the absence of mitosis, resulting in nuclei with multiples of 2C DNA amounts (4C, 8C, 16C, etc.). In some orchids, a disproportionate increase in nuclear DNA contents has been observed, where successive endoreduplication cycles result in DNA amounts 2C + P, 2C + 3P, 2C + 7P, etc., where P is the DNA content of the replicated part of the 2C nuclear genome. This unique phenomenon was termed "progressively partial endoreplication" (PPE). We investigated processes behind the PPE in Ludisia discolor using flow cytometry (FCM) and Illumina sequencing. In particular, we wanted to determine whether chromatin elimination or incomplete genome duplication was involved, and to identify types of DNA sequences that were affected. Cell cycle analysis of root tip cell nuclei pulse-labeled with EdU revealed two cell cycles, one ending above the population of nuclei with 2C + P content, and the other with a typical "horseshoe" pattern of S-phase nuclei ranging from 2C to 4C DNA contents. The process leading to nuclei with 2C + P amounts therefore involves incomplete genome replication. Subsequent Illumina sequencing of flow-sorted 2C and 2C + P nuclei showed that all types of repetitive DNA sequences were affected during PPE; a complete elimination of any specific type of repetitive DNA was not observed. We hypothesize that PPE is part of a highly controlled transition mechanism from proliferation phase to differentiation phase of plant tissue development.

• MeSH
• buněčné jádro genetika   MeSH
• endoreduplikace genetika   MeSH
• genom rostlinný MeSH
• listy rostlin genetika   MeSH
• mitóza genetika   MeSH
• Orchidaceae genetika   MeSH
• polyploidie MeSH
• průtoková cytometrie metody   MeSH
• replikace DNA genetika   MeSH
• vysoce účinné nukleotidové sekvenování metody   MeSH
• Publikační typ
• časopisecké články MeSH

Nuclear genome size is an inherited quantitative trait of eukaryotic organisms with both practical and biological consequences. A detailed analysis of major families is a promising approach to fully understand the biological meaning of the extensive variation in genome size in plants. Although Orchidaceae accounts for ∼10% of the angiosperm diversity, the knowledge of patterns and dynamics of their genome size is limited, in part due to difficulties in flow cytometric analyses. Cells in various somatic tissues of orchids undergo extensive endoreplication, either whole-genome or partial, and the G1-phase nuclei with 2C DNA amounts may be lacking, resulting in overestimated genome size values. Interpretation of DNA content histograms is particularly challenging in species with progressively partial endoreplication, in which the ratios between the positions of two neighboring DNA peaks are lower than two. In order to assess distributions of nuclear DNA amounts and identify tissue suitable for reliable estimation of nuclear DNA content, we analyzed six different tissue types in 48 orchid species belonging to all recognized subfamilies. Although traditionally used leaves may provide incorrect C-values, particularly in species with progressively partial endoreplication, young ovaries and pollinaria consistently yield 2C and 1C peaks of their G1-phase nuclei, respectively, and are, therefore, the most suitable parts for genome size studies in orchids. We also provide new DNA C-values for 22 orchid genera and 42 species. Adhering to the proposed methodology would allow for reliable genome size estimates in this largest plant family. Although our research was limited to orchids, the need to find a suitable tissue with dominant 2C peak of G1-phase nuclei applies to all endopolyploid species.

• MeSH
• buněčné jádro genetika   MeSH
• délka genomu MeSH
• DNA rostlinná genetika   MeSH
• endoreduplikace genetika   MeSH
• genom rostlinný * MeSH
• listy rostlin genetika   MeSH
• Orchidaceae genetika   MeSH
• průtoková cytometrie * MeSH
• Publikační typ
• časopisecké články MeSH
• práce podpořená grantem MeSH

BACKGROUND AND AIMS: Patterns of ploidy variation among and within populations can provide valuable insights into the evolutionary mechanisms shaping the dynamics of plant systems showing ploidy diversity. Whereas data on majority ploidies are, by definition, often sufficiently extensive, much less is known about the incidence and evolutionary role of minority cytotypes. METHODS: Ploidy and proportions of endoreplicated genome were determined using DAPI (4',6-diamidino-2-phenylindole) flow cytometry in 6150 Gymnadenia plants (fragrant orchids) collected from 141 populations in 17 European countries. All widely recognized European species, and several taxa of less certain taxonomic status were sampled within Gymnadenia conopsea sensu lato. KEY RESULTS: Most Gymnadenia populations were taxonomically and/or ploidy heterogeneous. Two majority (2x and 4x) and three minority (3x, 5x and 6x) cytotypes were identified. Evolution largely proceeded at the diploid level, whereas tetraploids were much more geographically and taxonomically restricted. Although minority ploidies constituted <2 % of the individuals sampled, they were found in 35 % of populations across the entire area investigated. The amount of nuclear DNA, together with the level of progressively partial endoreplication, separated all Gymnadenia species currently widely recognized in Europe. CONCLUSIONS: Despite their low frequency, minority cytotypes substantially increase intraspecific and intrapopulation ploidy diversity estimates for fragrant orchids. The cytogenetic structure of Gymnadenia populations is remarkably dynamic and shaped by multiple evolutionary mechanisms, including both the ongoing production of unreduced gametes and heteroploid hybridization. Overall, it is likely that the level of ploidy heterogeneity experienced by most plant species/populations is currently underestimated; intensive sampling is necessary to obtain a holistic picture.

• MeSH
• biologická evoluce * MeSH
• chromozomy rostlin genetika   MeSH
• cytogenetika MeSH
• endoreduplikace MeSH
• genetická variace * MeSH
• genom rostlinný genetika   MeSH
• hybridizace genetická MeSH
• Orchidaceae klasifikace   cytologie   genetika   MeSH
• polyploidie * MeSH
• průtoková cytometrie MeSH
• zeměpis MeSH
• Publikační typ
• časopisecké články MeSH
• práce podpořená grantem MeSH
• Geografické názvy
• Evropa MeSH

In angiosperms, genome size and nucleobase composition (GC content) exhibit pronounced variation with possible adaptive consequences. The hyperdiverse orchid family possessing the unique phenomenon of partial endoreplication (PE) provides a great opportunity to search for interactions of both genomic traits with the evolutionary history of the family. Using flow cytometry, we report values of both genomic traits and the type of endoreplication for 149 orchid species and compare these with a suite of life-history traits and climatic niche data using phylogeny-based statistics. The evolution of genomic traits was further studied using the Brownian motion (BM) and Ornstein-Uhlenbeck (OU) models to access their adaptive potential. Pronounced variation in genome size (341-54 878 Mb), and especially in GC content (23.9-50.5%), was detected among orchids. Diversity in both genomic traits was closely related to the type of endoreplication, plant growth form and climatic conditions. GC content was also associated with the type of dormancy. In all tested scenarios, OU models always outperformed BM models. Unparalleled GC content variation was discovered in orchids, setting new limits for plants. Our study indicates that diversity in both genome size and GC content has adaptive consequences and is tightly linked with evolutionary transitions to PE.

• MeSH
• biologická adaptace MeSH
• biologická evoluce MeSH
• délka genomu * MeSH
• endoreduplikace * MeSH
• fylogeneze MeSH
• genom rostlinný * MeSH
• modely genetické MeSH
• Orchidaceae genetika   MeSH
• podnebí MeSH
• zastoupení bazí MeSH
• Publikační typ
• časopisecké články MeSH
• práce podpořená grantem MeSH

Wild barley is abundant, occupying large diversity of sites, ranging from the northern mesic Mediterranean meadows to the southern xeric deserts in Israel. This is also reflected in its wide phenotypic heterogeneity. We investigated the dynamics of DNA content changes in seed tissues in ten wild barley accessions that originated from an environmental gradient in Israel. The flow cytometric measurements were done from the time shortly after pollination up to the dry seeds. We show variation in mitotic cell cycle and endoreduplication dynamics in both diploid seed tissues (represented by seed maternal tissues and embryo) and in the triploid endosperm. We found that wild barley accessions collected at harsher xeric environmental conditions produce higher proportion of endoreduplicated nuclei in endosperm tissues. Also, a comparison of wild and cultivated barley strains revealed a higher endopolyploidy level in the endosperm of wild barley, that is accompanied by temporal changes in the timing of the major developmental phases. In summary, we present a new direction of research focusing on connecting spatiotemporal patterns of endoreduplication in barley seeds and possibly buffering for stress conditions.

• MeSH
• DNA rostlinná genetika   MeSH
• endosperm genetika   MeSH
• genetická variace genetika   MeSH
• ječmen (rod) genetika   MeSH
• polyploidie MeSH
• populační genetika metody   MeSH
• semena rostlinná genetika   MeSH
• Publikační typ
• časopisecké články MeSH
• práce podpořená grantem MeSH
• Geografické názvy
• Izrael MeSH

p16ink4 and pRb, two components of a key G1/S regulatory pathway, and tumor suppressors commonly targeted in oncogenesis, are among the candidates for gene therapy of cancer. Wild-type p16 and a constitutively active pRb(delta cdk) mutant both blocked G1 in short-term experiments, but only p16 imposed a sustained G1 arrest. Unexpectedly, cells conditionally exposed to pRb(delta cdk) entered S phase after 2 days, followed by endoreduplication between days 4-6. The distinct phenotypes evoked by p16 vs pRb(delta cdk) appear mediated by cyclin E/CDK2 which, while active in the pRb(delta cdk)-expressing cells, became rapidly inhibited through restructuring diverse cyclin/CDK/p21 complexes by p16. These results provide novel insights into the roles of p16, pRb and cyclin E in G1/S control and multistep oncogenesis, with implications for gene therapy strategies.

• MeSH
• cyklin-dependentní kinasa 2 MeSH
• cyklin-dependentní kinasy biosyntéza   metabolismus   MeSH
• G1 fáze genetika   fyziologie   MeSH
• inhibitor p16 cyklin-dependentní kinasy biosyntéza   genetika   fyziologie   MeSH
• inhibitory růstu genetika   fyziologie   MeSH
• kinasy CDC2-CDC28 * MeSH
• krysa rodu rattus MeSH
• lidé MeSH
• nádorová transformace buněk genetika   metabolismus   MeSH
• nádorové buňky kultivované MeSH
• osteosarkom MeSH
• protein-serin-threoninkinasy biosyntéza   metabolismus   MeSH
• retinoblastomový protein biosyntéza   genetika   fyziologie   MeSH
• S fáze genetika   MeSH
• technika přenosu genů MeSH
• zvířata MeSH
• Check Tag
• krysa rodu rattus MeSH
• lidé MeSH
• zvířata MeSH
• Publikační typ
• časopisecké články MeSH
• práce podpořená grantem MeSH
• srovnávací studie MeSH

Vertebrate erythrocytes and thrombocytes arise from the common bipotent thrombocytic-erythroid progenitors (TEPs). Even though nonmammalian erythrocytes and thrombocytes are phenotypically very similar to each other, mammalian species have developed some key evolutionary improvements in the process of erythroid and thrombocytic differentiation, such as erythroid enucleation, megakaryocyte endoreduplication, and platelet formation. This brings up a few questions that we try to address in this review. Specifically, we describe the ontology of erythro-thrombopoiesis during adult hematopoiesis with focus on the phylogenetic origin of mammalian erythrocytes and thrombocytes (also termed platelets). Although the evolutionary relationship between mammalian and nonmammalian erythroid cells is clear, the appearance of mammalian megakaryocytes is less so. Here, we discuss recent data indicating that nonmammalian thrombocytes and megakaryocytes are homologs. Finally, we hypothesize that erythroid and thrombocytic differentiation evolved from a single ancestral lineage, which would explain the striking similarities between these cells.

• MeSH
• buněčná diferenciace fyziologie   MeSH
• erytrocyty cytologie   MeSH
• lidé MeSH
• megakaryocyty cytologie   MeSH
• obratlovci fyziologie   MeSH
• trombocyty cytologie   MeSH
• zvířata MeSH
• Check Tag
• lidé MeSH
• zvířata MeSH
• Publikační typ
• časopisecké články MeSH
• práce podpořená grantem MeSH
• přehledy MeSH