Origin of Life: Emergence, Self-organization and Evolution
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Origin of Life: Emergence, Self-organization and Evolution
A system-centered perspective on the origin and evolution of Life on Earth
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Noise, Stochasticity and Evolvability

Noise, Stochasticity and Evolvability | Origin of Life: Emergence, Self-organization and Evolution | Scoop.it

Kuwahara and Soyer report about stochastic fluctuations in gene regulation that can lead to increased evolvability of biological systems by pushing "system parameters toward a nonlinear regime where phenotypic diversity is increased and small changes in genotype cause large changes in expression level".

These findings strongly suggest that stochasticity and noise are used by biosystems to increase plasticity and access new phenotypes.

 

Source:

Hiroyuki Kuwahara & Orkun S Soyer. Bistability in feedback circuits as a byproduct of evolution of evolvability. Molecular Systems Biology 8:564

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Evidence of non-random mutation rates suggests an evolutionary risk management strategy

Evidence of non-random mutation rates suggests an evolutionary risk management strategy | Origin of Life: Emergence, Self-organization and Evolution | Scoop.it

A central tenet in evolutionary theory is that mutations occur randomly in the genome, now Luscombe and co-workers show that “neutral mutation rate varies by more than an order of magnitude across 2,659 genes” and surprisingly this variation is not random. Researchers detected a lower rate in highly expressed genes and in those undergoing stronger purifying selection. These findings suggest that the mutation rate has been evolutionarily optimized to reduce the risk of deleterious mutations. It seems like that bacteria have evolved a mechanism that protects important genes from random mutation, effectively reducing the risk of self-destruction.

 

Source:

Iñigo Martincorena, Aswin S. N. Seshasayee & Nicholas M. Luscombe

Evidence of non-random mutation rates suggests an evolutionary risk management strategy

Nature, 22 April 2012

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How does innovation arise in biological systems?

How does innovation arise in biological systems? | Origin of Life: Emergence, Self-organization and Evolution | Scoop.it

How does innovation arise in biological systems? A typical example is the emergence of novel catalytic functions in enzymes.

Hereafter I report two studies that come to contradicting conclusions.

Axe and Gauger suggest that the number of simultaneous mutations required to convert a 2-amino-3-ketobutyrate CoA ligase (Kbl2) to 8-amino-7-oxononanoate synthase (BioF2) are so many changes that it becomes probable only “on timescales much longer than the age of life on earth”.

Conversely, Jez and Penning showed that a single mutation changes D4-3-ketosteroid-5b-reductase to 3a-HSD; where Sommerville and coworkers have proved that six substitutions are sufficient to convert a hydroxylase to a desaturase.

How do we account for such contradicting results?

Does evolvability inversely correlate with specificity and catalytic proficiency?

Shall an enzyme be suboptimal adapted to its function in order to evolve new functions?

Does this apply to whole organism?

 

By Davide De Lucrezia

 

Source:

Gauger AK and Axe DD. The Evolutionary Accessibility of New Enzymes Functions: A Case Study from the Biotin Pathway. BIO-Complexity, Vol 2011

 

Jez JM and Penning TM. Engineering steroid 5b-reductase activity into rat liver 3a-hydroxysteroid ehydrogenase. Biochemistry 1998, 37:9695-9705.

 

Broun P, Shanklin J, Whittle E and Somerville C. Catalytic plasticity of fatty acid modification enzymes underlying chemical diversity of plant lipids. Science 1998, 282:1315-1317.

 

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