37,683 research outputs found
Phenotypic variation in Calandrinia galapagosa (Portulacaceae)
Calandrinia galapagosa St. John is found only on San
Cristóbal Island in the Galápagos archipelago, where it is
severely threatened by feral goats. A population at Cerro
Colorado is protected by an exclosure constructed for this
purpose in 1993. Individuals of this population have white
or pinkish white flowers with a green stem, whereas the
population at La Galapaguera, has pinkish white flowers
with a purple stem
Inhomogeneities in 3 dimensional oscillatory media
We consider localized perturbations to spatially homogeneous oscillations in
dimension 3 using the complex Ginzburg-Landau equation as a prototype. In
particular, we will focus on heterogeneities that locally change the phase of
the oscillations. In the usual translation invariant spaces and at the linearization about these spatially homogeneous solutions
result in an operator with zero eigenvalue embedded in the essential spectrum.
In contrast, we show that when considered as an operator between Kondratiev
spaces, the linearization is a Fredholm operator. These spaces consist of
functions with algebraical localization that increases with each derivative. We
use this result to construct solutions close to the equilibrium via the
Implicit Function Theorem and derive asymptotics for wavenumbers in the far
field.Comment: 3 figures, 15 pages. More accurate numerical results. Added a figure
illustrating the decay of Amplitude of solution
Automated design of bacterial genome sequences
Background:
Organisms have evolved ways of regulating transcription to better adapt to varying environments. Could the current functional genomics data and models support the possibility of engineering a genome with completely rearranged gene organization while the cell maintains its behavior under environmental challenges? How would we proceed to design a full nucleotide sequence for such genomes?
Results:
As a first step towards answering such questions, recent work showed that it is possible to design alternative transcriptomic models showing the same behavior under environmental variations than the wild-type model. A second step would require providing evidence that it is possible to provide a nucleotide sequence for a genome encoding such transcriptional model. We used computational design techniques to design a rewired global transcriptional regulation of Escherichia coli, yet showing a similar transcriptomic response than the wild-type. Afterwards, we “compiled” the transcriptional networks into nucleotide sequences to obtain the final genome sequence. Our computational evolution procedure ensures that we can maintain the genotype-phenotype mapping during the rewiring of the regulatory network. We found that it is theoretically possible to reorganize E. coli genome into 86% fewer regulated operons. Such refactored genomes are constituted by operons that contain sets of genes sharing around the 60% of their biological functions and, if evolved under highly variable environmental conditions, have regulatory networks, which turn out to respond more than 20% faster to multiple external perturbations.
Conclusions:
This work provides the first algorithm for producing a genome sequence encoding a rewired transcriptional regulation with wild-type behavior under alternative environments
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