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Hidden genetic variations power evolutionary leaps



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Laboratory populations that quietly amass 'cryptic' are known as evolutionary leaps, according to a paper in the July 26 issue of Science . A better understanding of cryptic variation may improve the development of techniques for developing new biomolecules for medical and other applications.
                                               

Genetic variation-that is, accumulated mutations in the DNA is the fuel for all evolutionary change: the more genetic variation, the faster evolution works and the more possibilities for novel adaptive solutions.

But one kind of genetic variation -Hidden, or "cryptic," does not alter the appearance or behavior of an organism in its usual environment.

"It's an underappreciated child of genetic variation," says corresponding author, Andreas Wagner, an evolutionary biologist at the University of Zurich and external professor at the Santa Fe Institute,

Previous work has shown that cryptic variation in natural populations promotes rapid evolutionary adaptation. But the underlying molecular mechanisms were unclear.

To explore those mechanisms, Wagner's team worked with populations of the good bacterium E. coli that carried a plasmid with a gene for a yellow fluorescent protein (YFP). The team designed a two-stage experiment. In stage 1

, they used mutagenic PCR to increase variation in the YFP gene. Simultaneously, they are selected for a narrow range of yellow fluorescence. Any bacteria not sufficiently yellow were excluded, a process called 'stabilizing selection.' In this way, they are using cryptographic genetic modification without altering the yellow color of the YFP protein.

During stage 2, the team changed the selection rules and started selecting E. coli that fluoresces in the green part of the spectrum ('directional selection'). They also introduced control populations of E. coli that lacked enhanced cryptic variation in YFP. The E. coli cell lines with stores of cryptic variation green fluorescent protein (from YFP genes) that were both greener and genetically more diverse than any produced by the control E. coli lineages.

In the experiment, says co-author Joshua Payne (ETH Zurich), cryptic variation did more than drive evolutionary adaptation faster. Green lines YFP proteins, forms of the protein that were inaccessible to regular bacteria, and they evolved by multiple unique routes not available to regular E. coli .

Current laboratory directed evolution often leads to the same evolutionary outcomes each time. Jia Zheng, postdoctoral researcher at the University of Zurich.

In the wild, cryptic variation helps fish to adapt to life in caves. In the lab, cryptic variation might help a biomolecule bind a new receptor. Zheng.

Like a fat savings account, cryptic variation is also available in an emergency to fuel rapid evolutionary change critical to the survival of a lineage and useful for molecular biologists.
                                                                                                                        


Unknown Costa Rican frog hidden amongst a widespread species


More information:
J. Zheng el al., "Cryptic genetic variation accelerates evolution by opening access to various adaptive peaks," Science (2019). science.sciencemag.org/cgi/doi … 1126 / science.aax1837

Provided by
Santa Fe Institute




Citation :
                                                 Hidden genetic variations power evolutionary leaps (2019, July 25)
                                                 retrieved 26 July 2019
                                                 from https://phys.org/news/2019-07-hidden-genetic-variations-power-evolutionary.html
                                            

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