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31.
Does host‐plant diversity explain species richness in insects? A test using Coccidae (Hemiptera)
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1. The megadiverse herbivores and their host plants are a major component of biodiversity, and their interactions have been hypothesised to drive the diversification of both. 2. If plant diversity influences the diversity of insects, there is an expectation that insect species richness will be strongly correlated with host‐plant species richness. This should be observable at two levels (i) more diverse host‐plant groups should harbour more species of insects, and (ii) the species richness of a group of insects should correlate with the richness of the host groups it uses. However, such a correlation is also consistent with a hypothesis of random host use, in which insects encounter and use hosts in proportion to the diversity of host plants. Neither of these expectations has been widely tested. 3. These expectations were tested using data from a species‐rich group of insects – the Coccidae (Hemiptera). 4. Significant positive correlations were found between the species richness of coccid clades (genera) and the species richness of the host‐plant family or families upon which the clades occur. On a global scale, more closely related plant families have more similar communities of coccid genera but the correlation is weak. 5. Random host use could not be rejected for many coccids but randomisation tests and similarity of coccid communities on closely related plant families show that there is non‐random host use in some taxa. Overall, our results support the idea that plant diversity is a driver of species richness of herbivorous insects, probably via escape‐and‐radiate or oscillation‐type processes. 相似文献
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PO TIEN XIUHUA ZHANG BINGSHENG QIU BINGYI QIN GUSUI WU 《The Annals of applied biology》1987,111(1):143-152
Two virus-protecting strains, S51 and S52, were obtained for the control of cucumber mosaic virus (CMV) by local lesion selection after adding satellite RNA to the RNA genome of CMV. Both were found to protect pepper plants against a virulent strain of CMV under greenhouse and field conditions. Results from 14 localities in China indicated that the use of protective strains decreased the disease index by 21.6% to 82.8% and increased fruit yields by 10.8% to 55.6%. The host reactions and safety of S51 and S52 were tested, and the effects of the strains on plant growth were also investigated. Possible mechanisms of control of CMV-caused plant diseases by mild strains are discussed. 相似文献
33.
Identification of a potent MAR element from the mouse genome and assessment of its activity in stable and transient transfections 总被引:1,自引:0,他引:1
Matrix attachment regions are DNA sequences found throughout eukaryotic genomes that are believed to define boundaries interfacing heterochromatin and euchromatin domains, thereby acting as epigenetic regulators. When included in expression vectors, MARs can improve and sustain transgene expression, and a search for more potent novel elements is therefore actively pursued to further improve recombinant protein production. Here we describe the isolation of new MARs from the mouse genome using a modified in silico analysis. One of these MARs was found to be a powerful activator of transgene expression in stable transfections. Interestingly, this MAR also increased GFP and/or immunoglobulin expression from some but not all expression vectors in transient transfections. This effect was attributed to the presence or absence of elements on the vector backbone, providing an explanation for earlier discrepancies as to the ability of this class of elements to affect transgene expression under such conditions. 相似文献
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Biological control agents (BCAs) composed of attenuated cucumber mosaic (CMV) and its satellite RNA for controlling CMV diseases were found to induce plant resistance to a number of fungal diseases. Tests conducted in both the field and greenhouse showed evident protective effects against fungal infections by the BCAs. Artificial inoculation with a fungal spore suspension using BCA-treated plants, satellite transgenic plants and plants infected with CMV alone indicated that the resistance to fungi was induced by the virus infection, not by the presence of satellite RNA. 相似文献
36.
A genetic algorithm for maximum-likelihood phylogeny inference using nucleotide sequence data 总被引:6,自引:2,他引:4
Phylogeny reconstruction is a difficult computational problem, because the
number of possible solutions increases with the number of included taxa.
For example, for only 14 taxa, there are more than seven trillion possible
unrooted phylogenetic trees. For this reason, phylogenetic inference
methods commonly use clustering algorithms (e.g., the neighbor-joining
method) or heuristic search strategies to minimize the amount of time spent
evaluating nonoptimal trees. Even heuristic searches can be painfully slow,
especially when computationally intensive optimality criteria such as
maximum likelihood are used. I describe here a different approach to
heuristic searching (using a genetic algorithm) that can tremendously
reduce the time required for maximum-likelihood phylogenetic inference,
especially for data sets involving large numbers of taxa. Genetic
algorithms are simulations of natural selection in which individuals are
encoded solutions to the problem of interest. Here, labeled phylogenetic
trees are the individuals, and differential reproduction is effected by
allowing the number of offspring produced by each individual to be
proportional to that individual's rank likelihood score. Natural selection
increases the average likelihood in the evolving population of phylogenetic
trees, and the genetic algorithm is allowed to proceed until the likelihood
of the best individual ceases to improve over time. An example is presented
involving rbcL sequence data for 55 taxa of green plants. The genetic
algorithm described here required only 6% of the computational effort
required by a conventional heuristic search using tree
bisection/reconnection (TBR) branch swapping to obtain the same
maximum-likelihood topology.
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K Rose R St?cklin L A Savoy P O Regamey R E Offord P Vuagnat J Markussen 《Protein engineering》1991,4(4):409-412
The production of semisynthetic human insulin for therapeutic purposes is of considerable importance. During trypsin-catalysed transformation of pig insulin into an ester of insulin of human sequence, the alanyl residue at position B30 is removed and replaced with an esterified residue of threonine. We have carried out this transformation in a medium enriched in 18OH2 and studied the product by MS. In contrast to a previous report, we find that incorporation of label into the B29 - B30 peptide bond occurs during the transformation with threonine methyl ester in aqueous N,N-dimethylacetamide. Quantitative data are presented and the implications of these findings are discussed. 相似文献
39.
April DeLaurier Nicholas Burton Michael Bennett Richard Baldock Duncan Davidson Timothy J Mohun Malcolm PO Logan 《BMC developmental biology》2008,8(1):83
Background
The developing mouse limb is widely used as a model system for studying tissue patterning. Despite this, few references are available that can be used for the correct identification of developing limb structures, such as muscles and tendons. Existing textual references consist of two-dimensional (2D) illustrations of the adult rat or mouse limb that can be difficult to apply when attempting to describe the complex three-dimensional (3D) relationship between tissues. 相似文献40.