БИОЛОГИЯ
How plastic is the transcriptome? - considerably more than genomes...
Current Biology, April 2006
Evolution: The Plastic Transcriptome
Studies across a wide range of species point to a surprising degree of plasticity in the transcriptional states that organisms can adopt, suggesting that organisms often respond to environmental challenges through wholesale reprogramming of their gene expression.
How plastic is the transcriptome? This is probably not a question that many of us have thought about much; yet it is fundamental to an understanding of how organisms adjust their physiology and behavior to cope with the diverse challenges posed by the environment. The literature on the topic is as yet quite slim, but one profound insight is beginning to emerge, namely that organisms can globally switch transcriptional states. Individuals in either state display considerably more divergent expression profiles than those seen across the geographic range of the species within a given state.
. . . . . . . . . .
The combined message from these diverse studies is that transcriptomes can adopt highly differentiated states involving large percentages of the genes expressed in a particular tissue. It is no longer surprising that single transcription factors can regulate the activity of batteries of hundreds of target genes; after all, this is how development is orchestrated. However, what is important here is that the magnitude and extent of the effects have been found to be large in comparison to genetic differentiation between individuals and even populations.
The relevance to evolutionary biology is that these findings once again remind us to look beneath the surface of the phenotype if we are to understand the forces shaping genetic variation. Much of the classical literature on phenotypic plasticity deals with polyphenism, which is the adoption of qualitatively distinct traits by different individuals of a species, such as winged and wingless castes of ants or horn size in beetles. Now we have a sense that polyphenism may indeed be prevalent at the molecular level across a broad array of organisms....
Widespread plasticity would imply greater potential for the balancing of variation: just as the sexes provide alternate physiological environments, so too should conditions of stress, behavioral caste, or other responses to environmental shifts.
Physiol. Genomics, April 2003
Evolutionary changes in heat-inducible gene expression in lines of E. coli adapted to high temperature
Nature, April 2006
Repeated morphological evolution through cis-regulatory changes in a pleiotropic gene
Repeated evolution of the same morphological trait is quite common, prompting the question whether evolution is constrained to follow certain paths, or whether there are many genetic routes to a phenotype. A study of the male wing pigmentation pattern involved in Drosophila courtship display shows that similar patterns arose independently at least twice and were lost at least five times in related Drosophila species. All these events involved regulatory changes at the yellow pigmentation gene but the two independent gains of wing spots resulted from co-option of different regulatory elements. Evolution went through the gene twice, but took a different route each time.
http://www.nature.com/nature/journal/v440/n7087/edsumm/e060420-13.html
Current Biology, April 2006
Evolution: The Plastic Transcriptome
Studies across a wide range of species point to a surprising degree of plasticity in the transcriptional states that organisms can adopt, suggesting that organisms often respond to environmental challenges through wholesale reprogramming of their gene expression.
How plastic is the transcriptome? This is probably not a question that many of us have thought about much; yet it is fundamental to an understanding of how organisms adjust their physiology and behavior to cope with the diverse challenges posed by the environment. The literature on the topic is as yet quite slim, but one profound insight is beginning to emerge, namely that organisms can globally switch transcriptional states. Individuals in either state display considerably more divergent expression profiles than those seen across the geographic range of the species within a given state.
. . . . . . . . . .
The combined message from these diverse studies is that transcriptomes can adopt highly differentiated states involving large percentages of the genes expressed in a particular tissue. It is no longer surprising that single transcription factors can regulate the activity of batteries of hundreds of target genes; after all, this is how development is orchestrated. However, what is important here is that the magnitude and extent of the effects have been found to be large in comparison to genetic differentiation between individuals and even populations.
The relevance to evolutionary biology is that these findings once again remind us to look beneath the surface of the phenotype if we are to understand the forces shaping genetic variation. Much of the classical literature on phenotypic plasticity deals with polyphenism, which is the adoption of qualitatively distinct traits by different individuals of a species, such as winged and wingless castes of ants or horn size in beetles. Now we have a sense that polyphenism may indeed be prevalent at the molecular level across a broad array of organisms....
Widespread plasticity would imply greater potential for the balancing of variation: just as the sexes provide alternate physiological environments, so too should conditions of stress, behavioral caste, or other responses to environmental shifts.
Physiol. Genomics, April 2003
Evolutionary changes in heat-inducible gene expression in lines of E. coli adapted to high temperature
Nature, April 2006
Repeated morphological evolution through cis-regulatory changes in a pleiotropic gene
Repeated evolution of the same morphological trait is quite common, prompting the question whether evolution is constrained to follow certain paths, or whether there are many genetic routes to a phenotype. A study of the male wing pigmentation pattern involved in Drosophila courtship display shows that similar patterns arose independently at least twice and were lost at least five times in related Drosophila species. All these events involved regulatory changes at the yellow pigmentation gene but the two independent gains of wing spots resulted from co-option of different regulatory elements. Evolution went through the gene twice, but took a different route each time.
http://www.nature.com/nature/journal/v440/n7087/edsumm/e060420-13.html