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Jakub Štenc Lukáš Janošík Eva Matoušková Jiří Hadrava Michael Mikát Zdeněk Janovský 《American journal of botany》2023,110(6):e16179
Premise
Animal-pollinated plants face a high risk of pollen loss during its transfer. To limit the negative effect of pollen losses by pollen consumption and heterospecific transfer, plant species may adjust and stratify their pollen availability during the day (i.e., “schedule” their pollen presentation) and attract pollinators in specific time frames.Methods
We investigated diurnal patterns of pollen availability and pollinator visitation in three coflowering plant species: Succisa pratensis with open flowers and accessible pollen, pollinated mainly by pollen-feeding hoverflies; Centaurea jacea with open flowers and less accessible pollen, pollinated mainly by pollen-collecting bees; and Trifolium hybridum with closed flowers and pollen accessible only after the active opening of the flower, pollinated exclusively by bees.Results
The three plant species differed in the peak pollen availability, tracked by the visitation activity of their pollinators. Succisa pratensis released all pollen in the morning, while pollinator activity was still low and peaked with a slight delay. In contrast, C. jacea and T. hybridum had distinct pollen presentation schedules, peaking in the early afternoon. The pollinator visitation to both of these species closely matched their pollen availability.Conclusions
Stratifying pollen availability to pollinators during the day may be one of several mechanisms that allow coflowering plants to share their pollinators and decrease the probability of heterospecific pollen transfer. 相似文献854.
Katherina Hell Arwyn Edwards Jakub Zarsky Sabine M Podmirseg Susan Girdwood Justin A Pachebat Heribert Insam Birgit Sattler 《The ISME journal》2013,7(9):1814-1826
Snow environments can occupy over a third of land surface area, but little is known about the dynamics of snowpack bacteria. The effect of snow melt on bacterial community structure and diversity of surface environments of a Svalbard glacier was examined using analyses of 16S rRNA genes via T-RFLP, qPCR and 454 pyrosequencing. Distinct community structures were found in different habitat types, with changes over 1 week apparent, in particular for the dominant bacterial class present, Betaproteobacteria. The differences observed were consistent with influences from depositional mode (snowfall vs aeolian dusts), contrasting snow with dust-rich snow layers and near-surface ice. Contrary to that, slush as the decompositional product of snow harboured distinct lineages of bacteria, further implying post-depositional changes in community structure. Taxa affiliated to the betaproteobacterial genus Polaromonas were particularly dynamic, and evidence for the presence of betaproteobacterial ammonia-oxidizing bacteria was uncovered, inviting the prospect that the dynamic bacterial communities associated with snowpacks may be active in supraglacial nitrogen cycling and capable of rapid responses to changes induced by snowmelt. Furthermore the potential of supraglacial snowpack ecosystems to respond to transient yet spatially extensive melting episodes such as that observed across most of Greenland''s ice sheet in 2012 merits further investigation. 相似文献
855.
Relics of Malva alcea are found in Central and Western Europe. A similar taxon, M. excisa, is native to the eastern parts of Europe. According to selected sources, the geographical range boundary of the above taxa intersects Poland. Taxonomic research relying on key morphological features (the depth of corolla petal incisions and the type of hairs covering the stem) did not clearly validate the distinctness of those species. Genetic variation between Malva alcea and M. excisa was analyzed using ISSR and ISJ markers. The performed analysis did not reveal statistically significant differences at the level of genetic diversity between M. alcea and M. excisa populations. The obtained genetic identity values (I = 0.985) do not support the identification of eastern populations as a distinct biological species of M. excisa. The applied DNA markers did not reveal species-specific bands supporting molecular identification of those taxa. The obtained genetic identity values were verified by neighbor-joining grouping which showed that M. alcea and M. excisa did not form corresponding clusters, thus pointing to an absence of significant differences between the analyzed taxa. Differences between the above species were not revealed by an analysis of the sequences of chloroplast regions trnHpsbA and rpoC1, either. 相似文献
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Jakub Jez Alexandra Castilho Josephine Grass Karola Vorauer-Uhl Thomas Sterovsky Friedrich Altmann Prof. Herta Steinkellner 《Biotechnology journal》2013,8(3):371-382
Recombinant human erythropoietin (rhEPO), a glycohormone, is one of the leading biopharmaceutical products. The production of rhEPO is currently restricted to mammalian cell expression systems because of rhEPO's highly complex glycosylation pattern, which is a major determinant for drug-efficacy. Here we evaluate the ability of plants to produce different glycoforms of rhEPO. cDNA constructs were delivered to Nicotiana benthamiana (N. benthamiana) and transiently expressed by a viral based expression system. Expression levels up to 85 mg rhEPO/kg fresh leaf material were achieved. Moreover, co-expression of rhEPO with six mammalian genes required for in planta protein sialylation resulted in the synthesis of rhEPO decorated mainly with bisialylated N-glycans (NaNa), the most abundant glycoform of circulating hEPO in patients with anemia. A newly established peptide tag (ELDKWA) fused to hEPO was particularly well-suited for purification of the recombinant hormone based on immunoaffinity. Subsequent lectin chromatography allowed enrichment of exclusively sialylated rhEPO. All plant-derived glycoforms exhibited high biological activity as determined by a cell-based receptor-binding assay. The generation of rhEPO carrying largely homogeneous glycosylation profiles (GnGnXF, GnGn, and NaNa) will facilitate further investigation of functionalities with potential implications for medical applications. 相似文献
858.
W. Lasek Wojciech Feleszko Jakub Goląb Tomasz Stokłosa Maria Marczak Anna Dąbrowska Magdalena Malejczyk Marek Jakóbisiak 《Cancer immunology, immunotherapy : CII》1997,45(2):100-108
There is strong evidence that antitumor activity of interleukin-12 (IL-12) in vivo is mediated, in part, through interferon
(IFNγ) produced by IL-12-stimulated natural killer and T cells. Since IFNγ and tumor necrosis factor α (TNFα) have been reported
to synergize in antitumor effects in a number of models, we decided to examine whether the combined treatment with recombinant
mouse IL-12 and recombinant human TNFα would produce similar effects. The efficacy of the combined IL-12/TNFα immunotherapy
was evaluated in three tumor models in mice: B16F10 melanoma, Lewis lung (LL/2) carcinoma and L1 sarcoma. Intratumoral daily
injections of 1 μg IL-12 in combination with 5 μg TNFα into B16F10-melanoma-bearing mice resulted in a significant retardation
of the tumor growth as compared with that in controls and in mice treated with either cytokine alone. Similar effects were
obtained using 0.1 μg IL-12 and 5 μg TNFα in LL/2 carcinoma and L1 sarcoma models. Antitumor activity against L1 sarcoma was
still preserved when TNFα at a low dose (1 μg) was combined with 0.1 μg IL-12 and applied for a prolonged time. Potentiation
of antitumor effects, which was observed in IL-12/TNFα-based immunotherapy, could result from at least three different mechanisms,
partly related to stimulation of IFNγ and TNFα production in treated mice: (a) direct cytostatic/cytotoxic effects on tumor
cells, (b) induction of antitumor activity of macrophages, and (c) inhibition of blood vessel formation in the tumor. Our
studies demonstrate that combination tumor immunotherapy with IL-12 and TNFα may be more effective than single-cytokine treatment,
and suggest possible mechanisms by which IL-12 and TNFα may exert potentiated therapeutic effects against locally growing
tumors.
Received: 17 February 1997 / Accepted: 5 August 1997 相似文献
859.