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991.
Claudio Capitao Sorin Tanasa Jaroslav Fulnecek Vivek K. Raxwal Svetlana Akimcheva Petra Bulankova Pavlina Mikulkova Lucie Crhak Khaitova Manikandan Kalidass Inna Lermontova Ortrun Mittelsten Scheid Karel Riha 《PLoS genetics》2021,17(9)
Meiosis in angiosperm plants is followed by mitotic divisions to form multicellular haploid gametophytes. Termination of meiosis and transition to gametophytic development is, in Arabidopsis, governed by a dedicated mechanism that involves SMG7 and TDM1 proteins. Mutants carrying the smg7-6 allele are semi-fertile due to reduced pollen production. We found that instead of forming tetrads, smg7-6 pollen mother cells undergo multiple rounds of chromosome condensation and spindle assembly at the end of meiosis, resembling aberrant attempts to undergo additional meiotic divisions. A suppressor screen uncovered a mutation in centromeric histone H3 (CENH3) that increased fertility and promoted meiotic exit in smg7-6 plants. The mutation led to inefficient splicing of the CENH3 mRNA and a substantial decrease of CENH3, resulting in smaller centromeres. The reduced level of CENH3 delayed formation of the mitotic spindle but did not have an apparent effect on plant growth and development. We suggest that impaired spindle re-assembly at the end of meiosis limits aberrant divisions in smg7-6 plants and promotes formation of tetrads and viable pollen. Furthermore, the mutant with reduced level of CENH3 was very inefficient haploid inducer indicating that differences in centromere size is not the key determinant of centromere-mediated genome elimination. 相似文献
992.
The life cycle of a new microsporidium, Octosporea collembolae, from the fat body of naturally infected springtails, Onychiurus quadriocellatus, is described at light and electron microscope levels. The prevalence of infection and host-parasite relationships are discussed. 相似文献
993.
Karel Mikulík Ivan Janda Jaroslav Weiser Anna Jirov 《Biochimica et Biophysica Acta (BBA) - Gene Structure and Expression》1982,699(3):203-210
Three different two-dimensional polyacrylamide gel electrophoretic systems were employed for identification of individual ribosomal proteins of Streptomyces aureofaciens. Proteins of small subunits were resolved into 21 spots. Larger ribosomal subunits contained 35 proteins. The separated ribosomal proteins from 50 S subunits were transferred on nitrocellulose membranes for immunochemical estimations. Antibodies developed against 50 S proteins of S. aureofaciens and Escherichia coli were used for identification of structural homologies between 50 S proteins of the two species. Results of the experiments indicate that about one half of the 50 S proteins of S. aureofaciens share common immunochemical determinants with corresponding proteins of 50 S subunits of E. coli. Evidence is presented that acidic ribosomal protein SL5 of large ribosomal subunits of S. aureofaciens can be assembled to E. coli P0 cores lacking proteins L7/L12. Reconstitution of the P0 cores with proteins SL5 or L7/L12 led to restoration of 78% activity in polyphenylalanine synthesis. 相似文献
994.
995.
This study is aimed at retention of K, Na, Mg, and Ca in two constructed wetlands (CWs) in the Czech Republic, and on the
evaluation of particular standing stocks in both above- and belowground plant biomass. The study revealed that CWs with horizontal
subsurface flow are not effective in retention of studied elements. Removal of K, Na, Mg, and Ca averaged only 10.6, 7.4,
6.1, and 1.4%, respectively. In general, concentrations of studied elements in various parts of Phragmites australis and Phalaris arundinacea were found within the range of concentrations reported from both natural and CWs. Aboveground standing stocks for K, Na and
Mg were comparable with those reported from natural stands for both Phalaris and Phragmites, but Ca aboveground standing stocks found in our study were lower compared to those found in several natural Phragmites wetlands. Aboveground to belowground standing stock ratio was generally >1.0. However, this amount formed usually <1% of
the annual inflow load of particular elements. The results of this study provide comprehensive information on retention and
sequestration of K, Na, Mg, and Ca in vegetation during municipal wastewater treatment in CWs with subsurface horizontal flow. 相似文献
996.
Jaroslav Kypr Hana Peňázová János Sági Šárka Pospíšilová Michaela Vorlíčková 《Journal of biomolecular structure & dynamics》2013,31(6):1225-1236
Abstract Alkaline agarose gel electrophoresis was used to detect UV-induced crosslinking of the strands of poly(dA-dT) and related alternating purine-pyrimidine DNAs in solutions stabilizing various polynucleotide conformations. Strands of the B-form and A-form of poly(dA-dT) were not crosslinked but a UV dose-dependent retarded species appeared in the denaturing gels in parallel with the polynucleotide isomerization into the unusual X-form. Most other polynucleotides adopting the X-form were crosslinked as well. The exceptions include the X-forms of poly(dA-butyl5dU) and poly(dA-pentyl5dU) whose strands do not crosslink because the long exocyclic substituents attached to uracil make the photodimerization impossible. Strands of poly (amino2dA-dT) and poly(dA, amino 2dA-dT), the latter polynucleotide containing roughly equal amounts of amino 2adenine and adenine, also do not crosslink upon UV irradiation because they isomerize into an A-like conformation which is different from the X- form of poly (dA-dT). In contrast, strands of the mixed copolymers of poly(dA, amino 2dA-dT) containing low amino 2adenine contents are crosslinked upon UV irradiation, in accordance with the observation that they isomerize into the X-form. 相似文献
997.
998.
Denisa Maceková Gustáv Ková? Jaroslav Hin?t Branislav Illek Jana Pere?ková ?elmíra Baro?ková Branislav Lí?ka 《Biologia》2009,64(2):409-413
Lipid peroxidation (LPX) can play an important role in the development of pathological changes of foetal and neonatal tissues.
We investigated LPX and biochemical parameters in plasma from mixed umbilical cord (m.u.c.) blood and acid-base balance (ABB)
parameters in m.u.c. blood of well-adapted full-term newborns. LPX products were estimated as thiobarbituric acid reacting
substances (TBARS) and were expressed by using of malondialdehyde (MDA) as a standard solution. Intensity of LPX was estimated
in vitro in m.u.c. blood plasma without and with added LPX activator (125 μM L-ascorbate plus 5 μM FeSO4) and in the incubated plasma (30 min, 37°C) under both conditions. Actual TBARS (3.51 ± 0.49 nmol/mL) were determined in
the non-incubated plasma without the added LPX activator. Approximately twice higher TBARS were found in the incubated plasma
without the LPX activator (7.29 ± 2.17 nmol/mL) or with it (8.57 ± 2.20 nmol/mL), as well as in the non-incubated plasma after
its addition (7.38 ± 1.98 nmol/mL). All analysed biochemical parameters (Fe, total iron-binding capacity, uric acid, proteins,
Mg, Ca, phosphate, glucose, K, Na, Cl, ALT, AST, GMT, CK, LD, HBD, AMS, ALP, ACP) and ABB parameters were within their reference
ranges. The actual TBARS levels were found being positively correlated with α-hydroxybutyrate dehydrogenase (HBD) activity and negatively with pO2. These results suggest that LPX in m.u.c. blood plasma might be activated. This activation could probably depend on extent
of hypoxia. TBARS and their formation in vitro could be suitable parameters of LPX in m.u.c. blood. 相似文献
999.
1000.
Böhmdorfer G Schleiffer A Brunmeir R Ferscha S Nizhynska V Kozák J Angelis KJ Kreil DP Schweizer D 《The Plant journal : for cell and molecular biology》2011,67(3):420-433
DNA double-strand breaks (DSBs) pose one of the most severe threats to genome integrity, potentially leading to cell death. After detection of a DSB, the DNA damage and repair response is initiated and the DSB is repaired by non-homologous end joining and/or homologous recombination. Many components of these processes are still unknown in Arabidopsis thaliana. In this work, we characterized γ-irradiation and mitomycin C induced 1 (GMI1), a member of the SMC-hinge domain-containing protein family. RT-PCR analysis and promoter-GUS fusion studies showed that γ-irradiation, the radio-mimetic drug bleocin, and the DNA cross-linking agent mitomycin C strongly enhance GMI1 expression particularly in meristematic tissues. The induction of GMI1 by γ-irradiation depends on the signalling kinase Ataxia telangiectasia-mutated (ATM) but not on ATM and Rad3-related (ATR). Epistasis analysis of single and double mutants demonstrated that ATM acts upstream of GMI1 while the atr gmi1-2 double mutant was more sensitive than the respective single mutants. Comet assay revealed a reduced rate of DNA double-strand break repair in gmi1 mutants during the early recovery phase after exposure to bleocin. Moreover, the rate of homologous recombination of a reporter construct was strongly reduced in gmi1 mutant plants upon exposure to bleocin or mitomycin C. GMI1 is the first member of its protein family known to be involved in DNA repair. 相似文献