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911.
912.
The relationship between seed size and fitness in plants may depend on offspring density, especially in cases where seed size affects the outcome of competition. We investigated the relationship between seed mass, germination, intraspecific competition and seedling height in a glasshouse experiment on three European white oak species (Quercus robur, Q. petraea, Q. pubescens). Within offspring families, seed mass showed a moderate, but statistically significant effect on seedling height, i.e. seedlings from heavier seeds were slightly taller. In contrast, competition caused pronounced inequality in seedling height in pairs of competing seedlings, but in only 55.2% of all pairs the dominant competitor arose from the heavier seed. It is thus possible that a positive effect of seed mass on seedling growth can be mediated through the density of conspecific seedlings and that heterogeneity in offspring density will contribute to the maintenance of seed mass variation in oak populations. 相似文献
913.
《Microbes and infection / Institut Pasteur》2014,16(8):623-632
Listeria monocytogenes is a facultative intracellular pathogen that causes gastroenteritis, meningitis, encephalitis and maternofetal infections. 20–30% of eubacterial ORFs are predicted to encode membrane proteins. The bacterial cytoplasmic membrane is a macromolecular structure, which plays a key role for the pathogenesis. Despite this, little knowledge exists regarding the function of cytoplasmic membrane proteins of Listeria during infection. Here, we investigated a predicted membrane protein of the pathogen L. monocytogenes, Lmo0412, of unknown function. Lmo0412 is only present in the Listeria genus and low conserved in the non-pathogenic species L. innocua. Bacterial fractionation and western blot analyses showed that Lmo0412 was only detectable in the membrane of L. monocytogenes EGDe during logarithmic growth phase. lmo0412 expression in L. monocytogenes was down-regulated during in vitro infection of JEG-3 epithelial cells. An L. monocytogenes mutant deficient in this membrane protein showed increased invasion of Caco-2 and NRK-49F host cells using in vitro infection models. Moreover, the lack of Lmo0412 in this deletion mutant increased the viable bacteria counts in the spleen and liver of mice compared to the wild type strain. Taken together, these data suggest a selective advantage conferred by the absence of Lmo0412 for the virulence of L. monocytogenes. 相似文献
914.
Levente Jozsef Keitaro Tashiro Andrew Kuo Eon Joo Park Athanasia Skoura Sebastian Albinsson Felix Rivera-Molina Kenneth D. Harrison Yasuko Iwakiri Derek Toomre William C. Sessa 《The Journal of biological chemistry》2014,289(13):9380-9395
Despite recent advances in understanding store-operated calcium entry (SOCE) regulation, the fundamental question of how ER morphology affects this process remains unanswered. Here we show that the loss of RTN4, is sufficient to alter ER morphology and severely compromise SOCE. Mechanistically, we show this to be the result of defective STIM1-Orai1 coupling because of loss of ER tubulation and redistribution of STIM1 to ER sheets. As a functional consequence, RTN4-depleted cells fail to sustain elevated cytoplasmic Ca2+ levels via SOCE and therefor are less susceptible to Ca2+ overload induced apoptosis. Thus, for the first time, our results show a direct correlation between ER morphology and SOCE and highlight the importance of RTN4 in cellular Ca2+ homeostasis. 相似文献
915.
N-terminal Proline-rich Domain Is Required for Scrambling Activity of Human Phospholipid Scramblases
Sarika Rayala Vincent G. Francis Ulaganathan Sivagnanam Sathyanarayana N. Gummadi 《The Journal of biological chemistry》2014,289(19):13206-13218
Human phospholipid scramblase 1 (hPLSCR1), a type II integral class membrane protein, is known to mediate bidirectional scrambling of phospholipids in a Ca2+-dependent manner. hPLSCR2, a homolog of hPLSCR1 that lacks N-terminal proline-rich domain (PRD), did not show scramblase activity. We attribute this absence of scramblase activity of hPLSCR2 to the lack of N-terminal PRD. Hence to investigate the above hypothesis, we added the PRD of hPLSCR1 to hPLSCR2 (PRD-hPLSCR2) and checked whether scramblase activity was restored. Functional assays showed that the addition of PRD to hPLSCR2 restored scrambling activity, and deletion of PRD in hPLSCR1 (ΔPRD-hPLSCR1) resulted in a lack of activity. These results suggest that PRD is crucial for the function of the protein. The effects of the PRD deletion in hPLSCR1 and the addition of PRD to hPLSCR2 were characterized using various spectroscopic techniques. Our results clearly showed that hPLSCR1 and PRD-hPLSCR2 showed Ca2+-dependent aggregation and scrambling activity, whereas hPLSCR2 and ΔPRD-hPLSCR1 did not show aggregation and activity. Thus we conclude that scramblases exhibit Ca2+-dependent scrambling activity by aggregation of protein. Our results provide a possible mechanism for phospholipid scrambling mediated by PLSCRs and the importance of PRD in its function and cellular localization. 相似文献
916.
Hiroyuki Ichida Ryouhei Morita Yuki Shirakawa Yoriko Hayashi Tomoko Abe 《The Plant journal : for cell and molecular biology》2019,98(2):301-314
Heavy‐ion beams have been widely utilized as a novel and effective mutagen for mutation breeding in diverse plant species, but the induced mutation spectrum is not fully understood at the genome scale. We describe the development of a multiplexed and cost‐efficient whole‐exome sequencing procedure in rice, and its application to characterize an unselected population of heavy‐ion beam‐induced mutations. The bioinformatics pipeline identified single‐nucleotide mutations as well as small and large (>63 kb) insertions and deletions, and showed good agreement with the results obtained with conventional polymerase chain reaction (PCR) and sequencing analyses. We applied the procedure to analyze the mutation spectrum induced by heavy‐ion beams at the population level. In total, 165 individual M2 lines derived from six irradiation conditions as well as eight pools from non‐irradiated ‘Nipponbare’ controls were sequenced using the newly established target exome sequencing procedure. The characteristics and distribution of carbon‐ion beam‐induced mutations were analyzed in the absence of bias introduced by visual mutant selections. The average (±SE) number of mutations within the target exon regions was 9.06 ± 0.37 induced by 150 Gy irradiation of dry seeds. The mutation frequency changed in parallel to the irradiation dose when dry seeds were irradiated. The total number of mutations detected by sequencing unselected M2 lines was correlated with the conventional mutation frequency determined by the occurrence of morphological mutants. Therefore, mutation frequency may be a good indicator for sequencing‐based determination of the optimal irradiation condition for induction of mutations. 相似文献
917.
评估淋巴瘤细胞MC/CAR、HUT78和RAMOS的CD52抗原呈现稳定性,并比较三种细胞用于抗CD52单抗活性检测中的优劣性。采用免疫荧光法检测淋巴瘤细胞MC/CAR、HUT78和RAMOS的CD52抗原呈现率,分析MC/CAR、HUT78和RAMOS传代培养5~20代CD52抗原呈现稳定性。分别以MC/CAR、HUT78和RAMOS作为抗CD52单抗结合活性和补体依赖细胞毒性的靶细胞进行检测,并比较其优劣性。结果显示,MC/CAR、RAMOS和HUT78的CD52抗原呈现率分别为95.5%、63.2%和38.3%。MC/CAR传代培养5~20代CD52抗原呈现率均大于90%。RAMOS传代培养5~13代CD52抗原呈现率介于60%~67%,第14~15代CD52抗原呈现率介于50%~60%,第16~20代细胞CD52抗原呈现率介于40%~50%。HUT78传代培养5~20代CD52抗原呈现率介于26.7%~38.9%。淋巴瘤细胞MC/CAR在抗CD52单抗的结合活性检测中呈现出更好的剂量依赖曲线。淋巴瘤细胞RAMOS在抗CD52单抗的补体依赖细胞毒性检测中呈现出更好的剂量效应曲线。CD52抗原呈现率方面MC/CAR>RAMOS>HUT78。结果表明,MC/CAR更适用于抗CD52单抗的结合活性的检测,RAMOS适用于抗CD52单抗的补体依赖细胞毒性检测。 相似文献
918.
Characterization of the Palmitoylation Domain of SNAP-25 总被引:3,自引:2,他引:3
Abstract: SNAP-25 (synaptosomal associated protein of 25 kDa) is a neural specific protein that has been implicated in the synaptic vesicle docking and fusion process. It is tightly associated with membranes, and it is one of the major palmitoylated proteins found in neurons. The functional role of palmitoylation for SNAP-25 is unclear. In this report, we show that the palmitate of SNAP-25 is rapidly turned over in PC12 cells, with a half-life of ∼3 h, and the half-life for the protein is 8 h. Mutation of Cys to Ser at positions 85, 88, 90, and 92 reduced the palmitoylation to 9, 21, 42, and 35% of the wild-type protein, respectively. Additional mutations of either Cys85,88 or Cys90,92 nearly abolished palmitoylation of the protein. A similar effect on membrane binding for the mutant SNAP-25 was observed, which correlated with the degree of palmitoylation. These results suggest that all four Cys residues are involved in palmitoylation and that membrane association of SNAP-25 may be regulated through dynamic palmitoylation. 相似文献
919.
Nobushige Ishida Tsendsuren Oyunsuren Suguru Mashima Harutaka Mukoyama Naruya Saitou 《Journal of molecular evolution》1995,41(2):180-188
The noncoding region between tRNAPro and the large conserved sequence block is the most variable region in the mammalian mitochondrial DNA D-loop region. This variable region (ca. 270 bp) of four species of Equus, including Mongolian and Japanese native domestic horses as well as Przewalskii's (or Mongolian) wild horse, were sequenced. These data were compared with our recently published Thoroughbred horse mitochondrial DNA sequences. The evolutionary rate of this region among the four species of Equus was estimated to be 2–4 × 10–8 per site per year. Phylogenetic trees of Equus species demonstrate that Przewalskii's wild horse is within the genetic variation among the domestic horse. This suggests that the chromosome number change (probably increase) of the Przewalskii's wild horse occurred rather recently.Correspondence to: N. Ishida 相似文献
920.
Cha CY Earm KH Youm JB Baek EB Kim SJ Earm YE 《Progress in biophysics and molecular biology》2008,96(1-3):399-420
In vascular smooth muscle cells, it has been suggested that membrane potential is an important component that initiates contraction. We developed a mathematical model to elucidate the quantitative contributions of major ion currents [a voltage-gated L-type Ca2+ current (ICaL), a voltage-sensitive K+ current (IKV), a Ca2+-activated K+ current (IKCa) and a nonselective cation current (INSC)] to membrane potential. In order to typify the diverse nature of pulmonary artery smooth muscle cells (PASMCs), we introduced parameters that are not fixed (variable parameters). The population of cells with different parameters was constructed and the cells that have the electrophysiological properties of PASMCs were selected. The contributions of each membrane current were investigated by sensitivity analysis and modification of the current parameters. Consequently, IKV and INSC were found to be the most important currents that affect the membrane potential. The occurrence of depolarisation in hypoxic pulmonary vasoconstriction (HPV) was also examined. In hypoxia, IKV and IKCa were reduced, but the consequent depolarisation in simulation was not enough to initiate contractions. If we add an increase of INSC (2.5-fold), the calculated membrane potential was enough to induce contraction. From the results, we conclude that the balance of various ion channel activities determines the resting membrane potential of PASMCs and our model was successful in explaining the depolarisation in HPV. Therefore, this model can be a powerful tool to investigate the various electrical properties of PASMCs in both normal and pathological conditions. 相似文献