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排序方式: 共有250条查询结果,搜索用时 15 毫秒
91.
Itay Cohen Tal Rapaport Vered Chalifa‐Caspi Shimon Rachmilevitch 《Physiologia plantarum》2019,165(4):755-767
Under natural conditions, plants are regularly exposed to combinations of stress factors. A common example is the conjunction between nitrogen (N) deficiency and excess light. The combined effect of stress factors is often ignored in studies using controlled conditions, possibly resulting in misleading conclusions. To address this issue, the present study examined the physiological behavior of Arabidopsis thaliana under the effect of varying nitrogen levels and light intensities. The joint influence of low N and excess light had an adverse effect on plant growth, chlorophyll and anthocyanin concentrations, photochemical capacity and the abundance of proteins involved in carbon assimilation and antioxidative metabolism. In contrast, no adverse physiological responses were observed for plants under either nitrogen limitation or high light (HL) intensity conditions (i.e. single stress). The underlying mechanisms for the increased growth in conditions of HL and sufficient nitrogen were a combination of chlorophyll accumulation and an increased number of proteins involved in C3 carbon assimilation, amino acids biosynthesis and chloroplast development. In contrast, combined stress conditions shifts plants from growth to survival by displaying anthocyanin accumulation and an increased number of proteins involved in catabolism of lipids and amino acids as energy substrates. Ultimately switching plants development from growth to survival. Our results suggest that an assessment of the physiological response to the combined effect of multiple stresses cannot be directly extrapolated from the physiological response to a single stress. Specifically, the synergistic interaction between N deficiency and saturating light in Arabidopsis plants could not have been modeled via only one of the stress factors. 相似文献
92.
Bareket Dassa Ilya Borovok Vered Ruimy-Israeli Raphael Lamed Harry J. Flint Sylvia H. Duncan Bernard Henrissat Pedro Coutinho Mark Morrison Pascale Mosoni Carl J. Yeoman Bryan A. White Edward A. Bayer 《PloS one》2014,9(7)
Background
A complex community of microorganisms is responsible for efficient plant cell wall digestion by many herbivores, notably the ruminants. Understanding the different fibrolytic mechanisms utilized by these bacteria has been of great interest in agricultural and technological fields, reinforced more recently by current efforts to convert cellulosic biomass to biofuels.Methodology/Principal Findings
Here, we have used a bioinformatics-based approach to explore the cellulosome-related components of six genomes from two of the primary fiber-degrading bacteria in the rumen: Ruminococcus flavefaciens (strains FD-1, 007c and 17) and Ruminococcus albus (strains 7, 8 and SY3). The genomes of two of these strains are reported for the first time herein. The data reveal that the three R. flavefaciens strains encode for an elaborate reservoir of cohesin- and dockerin-containing proteins, whereas the three R. albus strains are cohesin-deficient and encode mainly dockerins and a unique family of cell-anchoring carbohydrate-binding modules (family 37).Conclusions/Significance
Our comparative genome-wide analysis pinpoints rare and novel strain-specific protein architectures and provides an exhaustive profile of their numerous lignocellulose-degrading enzymes. This work provides blueprints of the divergent cellulolytic systems in these two prominent fibrolytic rumen bacterial species, each of which reflects a distinct mechanistic model for efficient degradation of cellulosic biomass. 相似文献93.
94.
DiGeorge syndrome (DGS), characterized genetically by a deletion within chromosome 22q11.2, is associated with a constellation of congenital heart defects. DiGeorge critical region 8 (Dgcr8), a gene that maps to the common deletion region of DGS, encodes a double stranded RNA-binding protein that is essential for miRNA biogenesis. To address the potential contribution of Dgcr8 insufficiency to cardiovascular development, we have inactivated Dgcr8 in cardiac neural crest cells (cNCCs). Dgcr8 mutants displayed a wide spectrum of malformations, including persistent truncus arteriosus (PTA) and ventricular septal defect (VSD). Interestingly, Dgcr8-null cNCCs that properly migrated into the cardiac outflow tract (OFT), proliferate normally and differentiate into vascular smooth muscle cells. However, loss of Dgcr8 causes a significant portion of the cNCCs to undergo apoptosis, causing a decrease in the pool of progenitors required for OFT remodeling. Our data uncover a new role of Dgcr8 in cardiovascular morphogenesis, plausibly as part of transmission mechanism for FGF-dependent survival cue for migrating cNCCs. 相似文献
95.
Berezin I Mizrachy-Dagry T Brook E Mizrahi K Elazar M Zhuo S Saul-Tcherkas V Shaul O 《Plant cell reports》2008,27(5):939-949
AtMHX is a vacuolar transporter encoded by a single gene in Arabidopsis. Electrophysiological analysis showed that it exchanges protons with Mg2+, Zn2+, and Fe2+ ions. The physiological impact of AtMHX was examined so far only in tissue-culture grown seedlings of tobacco plants overexpressing
this transporter. Here we investigated the impact of AtMHX on growth, response to different metals, and metal accumulation
of mature tobacco plants, as well as Arabidopsis plants in which we overexpressed this transporter. The analyses were carried out in hydroponic growth-systems, in which the
mineral composition could be effectively controlled, and the metal content of roots could be examined. Transformed tobacco
plants showed necrotic lesions and apical burnings upon growth with increased levels of Mg2+, Zn2+, and Cd2+ ions. This suggested that AtMHX can carry in planta not only Mg2+ and Zn2+ ions, as previously deduced based on observations in tissue-culture, but also Cd2+ ions. Transformed plants of both tobacco and Arabidopsis showed a reduction in plant size. However, the overall response of Arabidopsis to AtMHX overexpression was minor. No change was detected in the mineral content of any organ of the transgenic tobacco or
Arabidopsis plants. The necrotic lesions in tobacco resembled those seen in plants with perturbed proton balancing, raising the assumption
that AtMHX can affect the proton homeostasis of cells. In agreement with this assumption, the transformed tobacco plants had
increased expression and activity of the vacuolar H+-ATPase. The relative significance of AtMHX for metal and proton homeostasis still has to be elucidated. 相似文献
96.
Vered Holdengreber Cornelia Krieger Markus Gütlich Nikolas Schramek Michal Vechoropoulos Markus Fischer Adelbert Bacher Yehuda Ben-Shaul 《The journal of histochemistry and cytochemistry》2002,50(2):265-274
Tetrahydrobiopterin (BH4) is an essential co-factor for the biosynthesis of catecholamine-type neurotransmitters and of nitric oxide (NO). The expression of the enzymes catalyzing the first two steps of the BH4 biosynthetic pathway was studied in the developing chicken retina by in situ hybridization and immunocytochemistry. GTP-cyclohydrolase-I (GTP-CH-I) and 6-pyruvoyl-tetrahydropterin synthase (PTPS) were already expressed in the undifferentiated and proliferating retina of E7. At stage E11 both enzymes were expressed in photoreceptors, amacrine cells, displaced amacrine cells, and ganglion cells, and in the plexiform layers in which synaptic connections take place. At stage E18 the labeling was comparable to E11 but appeared to be more concentrated in photoreceptors and ganglion cells. 相似文献
97.
Roles of integrins and fibronectin in the entry of Streptococcus pyogenes into cells via protein F1 总被引:9,自引:5,他引:4
Vered Ozeri Ilan Rosenshine Deane F. Mosher Reinhard Fässler & Emanuel Hanski 《Molecular microbiology》1998,30(3):625-637
Entry of group A streptococcus (GAS) into cells has been suggested as an important trait in GAS pathogenicity. Protein F1, a fibronectin (Fn) binding protein, mediates GAS adherence to cells and the extracellular matrix, and efficient cell internalization. We demonstrate that the cellular receptors responsible for protein F1-mediated internalization of GAS are integrins capable of Fn binding. In HeLa cells, bacterial entry is blocked by anti-β1 integrin monoclonal antibody. In the mouse cell line GD25, a β1 null mutant, the αvβ3 integrin promotes GAS entry. Internalization of these cells by GAS is blocked by a peptide that specifically binds to αvβ3 integrin. In both cell lines, entry of GAS requires the occupancy of protein F1 by Fn. Neither the 29 kDa nor the 70 kDa N-terminal fragments or the 120 kDa cell-binding fragment of Fn promote bacterial entry. Fn-coated beads are taken up efficiently by HeLa cells. Both the entry of GAS via protein F1 and the uptake of Fn-coated beads are blocked by anti-β1 antibody but are unaffected by a large excess of soluble Fn. Internalization of HeLa cells by bacteria bearing increasing amounts of prebound Fn to protein F1 reveals a sigmoidal ultrasensitive curve. These suggest that the ability of particles to interact via Fn with multiple integrin sites plays a central role in their ability to enter cells. 相似文献
98.
Gottfried P Lotan O Kolot M Maslenin L Bendov R Gorovits R Yesodi V Yagil E Rosner A 《Plant molecular biology》2005,57(3):435-444
The gene encoding the wild type Integrase protein of coliphage HK022 was integrated chromosomally and expressed in Arabidopsis thaliana plants. Double-transgenic plants cloned with the int gene as well as with a T-DNA fragment carrying the proper att sites in a tandem orientation showed that Int catalyzed a site-specific integration reaction (attP × attB) as well as a site-specific excision reaction (attL × attR). The reactions took place without the need to provide any of the accessory proteins that are required by Int in the bacterial host. When expressed in tobacco plants a GFP-Int fusion exhibits a predominant nuclear localization.These authors contributed equally to this work 相似文献
99.
AtGA3ox2, a key gene responsible for bioactive gibberellin biosynthesis, is regulated during embryogenesis by LEAFY COTYLEDON2 and FUSCA3 in Arabidopsis 下载免费PDF全文
Curaba J Moritz T Blervaque R Parcy F Raz V Herzog M Vachon G 《Plant physiology》2004,136(3):3660-3669
Embryonic regulators LEC2 (LEAFY COTYLEDON2) and FUS3 (FUSCA3) are involved in multiple aspects of Arabidopsis (Arabidopsis thaliana) seed development, including repression of leaf traits and premature germination and activation of seed storage protein genes. In this study, we show that gibberellin (GA) hormone biosynthesis is regulated by LEC2 and FUS3 pathways. The level of bioactive GAs is increased in immature seeds of lec2 and fus3 mutants relative to wild-type level. In addition, we show that the formation of ectopic trichome cells on lec2 and fus3 embryos is a GA-dependent process as in true leaves, suggesting that the GA pathway is misactivated in embryonic mutants. We next demonstrate that the GA-biosynthesis gene AtGA3ox2, which encodes the key enzyme AtGA3ox2 that catalyzes the conversion of inactive to bioactive GAs, is ectopically activated in embryos of the two mutants. Interestingly, both beta-glucuronidase reporter gene expression and in situ hybridization indicate that FUS3 represses AtGA3ox2 expression mainly in epidermal cells of embryo axis, which is distinct from AtGA3ox2 pattern at germination. Finally, we show that the FUS3 protein physically interacts with two RY elements (CATGCATG) present in the AtGA3ox2 promoter. This work suggests that GA biosynthesis is directly controlled by embryonic regulators during Arabidopsis embryonic development. 相似文献
100.
Vered?NaorEmail author Jaime?Kigel Meira?Ziv Moshe?Flaishman 《Journal of Plant Growth Regulation》2004,23(4):269-279
The restricted flowering of colored cultivars ofZantedeschia is a consequence of developmental constraints imposed by apical dominance of the primary bud on secondary buds in the tuber,
and by the sympodial growth of individual shoots. GA3 enhances flowering inZantedeschia by increasing the number of flowering shoots per tuber and inflorescences per shoot. The effects of gibberellin on the pattern
of flowering and on the developmental fate of differentiated inflorescences along the tuber axis and individual shoot axes
were studied in GA3 and Uniconazole-treated tubers. Inflorescence primordia and fully developed (emerged) floral stems produced during tuber
storage and the plant growth period were recorded. Days to flowering, percent of flowering shoots and floral stem length decreased
basipetally along the shoot and tuber axes. GA3 prolonged the flowering period and increased both the number of flowering shoots per tuber and the differentiated inflorescences
per shoot. Activated buds were GA3 responsive regardless of meristem size or age. Uniconazole did not inhibit inflorescence differentiation but inhibited floral
stem elongation. The results suggest that GA3 has a dual action in the flowering process: induction of inflorescence differentiation and promotion of floral stem elongation.
The flowering pattern could be a result of a gradient in the distribution of endogenous factors involved in inflorescence
differentialtion (possibly GAs) and in floral stem growth. This gradient along the tuber and shoot axes is probably controlled
by apical dominance of the primary bud.
Online publication: 7 April 2005 相似文献