共查询到20条相似文献,搜索用时 15 毫秒
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High-dimensional switches have been proposed as a way to model cellular differentiation, particularly in the context of basic
Helix-Loop-Helix (bHLH) competitive heterodimerization networks. A previous study derived a simple rule showing how many elements
can be co-expressed, depending on the rate of competition within the network. A limitation to that rule, however, is that
many biochemical parameters were considered to be identical. Here, we derive a generalized rule. This in turns allows one
to study more ways in which these networks could be regulated, linking intrinsic cellular differentiation determinants to
extra-cellular cues. 相似文献
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Huxel GR 《Bulletin of mathematical biology》2007,69(6):2093-2104
The structure and dynamics of food webs are largely dependent upon interactions among consumers and their resources. However,
interspecific interactions such as intraguild predation and interference competition can also play a significant role in the
stability of communities. The role of antagonistic/synergistic interactions among predators has been largely ignored in food
web theory. These mechanisms influence predation rates, which is one of the key factors regulating food web structure and
dynamics, thus ignoring them can potentially limit understanding of food webs. Using nonlinear models, it is shown that critical
aspects of multiple predator food web dynamics are antagonistic/synergistic interactions among predators. The influence of
antagonistic/synergistic interactions on coexistence of predators depended largely upon the parameter set used and the degree
of feeding niche differentiation. In all cases when there was no effect of antagonism or synergism (a
ij
=1.00), the predators coexisted. Using the stable parameter set, coexistence occurred across the range of antagonism/synergism
used. However, using the chaotic parameter strong antagonism resulted in the extinction of one or both species, while strong
synergism tended to coexistence. Whereas using the limit cycle parameter set, coexistence was strongly dependent on the degree
of feeding niche overlap. Additionally increasing the degree of feeding specialization of the predators on the two prey species
increased the amount of parameter space in which coexistence of the two predators occurred. Bifurcation analyses supported
the general pattern of increased stability when the predator interaction was synergistic and decreased stability when it was
antagonistic. Thus, synergistic interactions should be more common than antagonistic interactions in ecological systems. 相似文献
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Indirect interactions among species emerge from the complexity of ecological networks and can strongly affect the response of communities to disturbances. To determine these indirect interactions and understand better community dynamics, ecologists focused on the interactions within small sets of species or modules. Thanks to their analytical tractability, modules bring insights on the mechanisms occurring in complex interaction networks. So far, most studies have considered modules with a single type of interaction although numerous species are involved in mutualistic and antagonistic interactions simultaneously. In this study, we analyse the dynamics of a diamond-shaped module with multiple interaction types: two resource species sharing a mutualist and a consumer. We describe the different types of indirect interaction occurring between the resource species and the conditions for a stable coexistence of all species. We show that the nature of indirect interactions between resource species (i.e. apparent facilitation, competition or antagonism), as well as stable coexistence, depend on the species generalism and asymmetry of interactions, or in other words, on the distribution of interaction strengths among species. We further unveil that a balance between mutualistic and antagonistic interactions at the level of resource species favours stable coexistence, and that species are more likely to coexist stably if there is apparent facilitation between the two resource species rather than apparent competition. Our results echo existing knowledge on the trophic diamond-shaped module, and confirm that our understanding of communities combining different interaction types can gain from module analyses. 相似文献
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Gross K 《Ecology letters》2008,11(9):929-936
Although positive interactions between species are well documented, most ecological theory for investigating multispecies coexistence remains rooted in antagonistic interactions such as competition and predation. Standard resource-competition models from this theory predict that the number of coexisting species should not exceed the number of factors that limit population growth. Here I show that positive interactions among resource competitors can produce species-rich model communities supported by a single limiting resource. Simulations show that when resource competitors reduce each others' per capita mortality rate (e.g. by ameliorating an abiotic stress), stable multispecies coexistence with a single resource may be common, even while the net interspecific interaction remains negative. These results demonstrate that positive interactions may provide an important mechanism for generating species-rich communities in nature. They also show that focusing on the net interaction between species may conceal important coexistence mechanisms when species simultaneously engage in both antagonistic and positive interactions. 相似文献
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Matter-Sadzinski L Matter JM Ong MT Hernandez J Ballivet M 《Development (Cambridge, England)》2001,128(2):217-231
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Phylogenetic analysis of plant basic helix-loop-helix proteins 总被引:14,自引:0,他引:14
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Members of the basic helix-loop-helix (bHLH) gene family play important roles in vertebrate neurogenesis. In this study, confocal microscopy-based fluorescence resonance energy transfer (FRET) is used to monitor bHLH protein-protein interactions under various physiological conditions. Tissue-specific bHLH activators, NeuroD 1, Mash 1, Neurogenin 1 (Ngn 1), Neurogenin2 (Ngn2), and ubiquitous expressed E47 protein are tagged with enhanced yellow fluorescence protein (EYFP) and enhanced cyan fluorescence protein (ECFP), respectively. The subcellular localization and mobility ofbHLH fusion proteins are examined in HEK293 cells. By transient transfection and in ovo electroporation, four pairs of tissue-specific bHLH activators and E47 protein are over-expressed in HEK293 cells and developing chick embryo neural tube. With the acceptor photobleaching method, FRET could be detected between these bHLH protein pairs in the nuclei of transfected cells and developing neural tubes. Mashl/E47 and Ngn2/E47 FRET pairs show higher FRET efficiencies in the medial and the lateral half of chick embryo neural tube, respectively. It suggests that these bHLH protein pairs formed functional DNA-protein complexes with regulatory elements of their downstream target genes in the specific regions. This work will help one understand the behaviours of bHLH factors in vivo. 相似文献
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