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Rahasia ' adaptasi ekstrem ' ditemukan di genom  python Burma  

Kemampuan python Burma untuk meningkatkan metabolisme dan memperbesar organ untuk menelan dan mencerna seluruh mangsa dapat ditelusuri ttg  evolusi yang luar biasa cepat dan adaptasi khusus gen dan cara mereka bekerja , sebuah tim internasional ahli biologi ...read more

Secrets to 'extreme adaptation' found in
Burmese python genome

Date:

December 2, 2013

Source:

University of Texas at Arlington

Summary:

The Burmese python's ability to ramp up its metabolism and enlarge its
organs to swallow and digest prey whole can be traced to unusually rapid
evolution and specialized adaptations of its genes and the way they work, an
international team of biologists says.

.......................

The Burmese python's ability to ramp up its metabolism and enlarge its
organs to swallow and digest prey whole can be traced to unusually rapid
evolution and specialized adaptations of its genes and the way they work, an
international team of biologists says in a new paper.

Lead author Todd Castoe, an assistant professor of biology at The University
of Texas at Arlington College of Science, and 38 co-authors from four countries
sequenced and analyzed the genome of the Burmese python, or Python
molurus bivittatus. Their work is scheduled for publication this week (Dec.
2) by theProceedings of the National Academy of Sciences along with
a companion paper on the sequencing and analysis of the king cobra (Ophiophagus
hannah). The papers represent the first complete and annotated snake
genomes.

Because snakes contain many of the same genes as other vertebrates,
studying how these genes have evolved to produce such extreme and unique
characteristics in snakes can eventually help explain how these genes function,
including how they enable extreme feats of organ remodeling. Such knowledge may
eventually be used to treat human diseases.

"One of the fundamental questions of evolutionary biology is how
vertebrates with all the same genes display such vastly different
characteristics. The Burmese python is a great way to study that because it is
so extreme," Castoe, who began working on the python project as a
postdoctoral fellow at the University of Colorado School of Medicine in the
laboratory of associate professor and paper corresponding author David D.
Pollock.

Castoe said: "We'd like to know how the snake uses genes we all have
to do things that no other vertebrates can do."

The new python study calls into question previous theories that major
obvious physical differences among species are caused primarily by changes in
gene expression. Instead, it contends that protein adaptation, gene expression
and changes in the structure of the organization of the genome itself are all
at work together in determining the unusual characteristics that define snakes,
and possibly other vertebrates.

Pollock said the python and king cobra studies represent a significant
addition to the field of "comparative systems genomics -- the evolutionary
analysis of multiple vertebrate genomes to understand how entire systems of
interacting genes can evolve from the molecules on up."

He said: "I believe that such studies are going to be fundamental to
our ability to understand what the genes in the human genome do, their
functional mechanisms, and how and why they came to be structured the way they
are."

The Burmese python's phenotype, or physical characteristics, represents one
of the most extreme examples of evolutionary adaptation, the authors said. Like
all snakes, its evolutionary origin included reduction in function of one lung
and the elongation of its mid-section, skeleton and organs. It also has an
extraordinary ability for what researchers call "physiological
remodeling."

Physiological remodeling refers to the process by which pythons are able to
digest meals much larger than their size, such as chickens or piglets, by ramping
up their metabolism and increasing the mass of their heart, liver, small
intestine and kidneys 35 percent to 150 percent in only 24 to 48 hours. As the
digestion is completed, the organs return to their original size within a
matter of days. The authors suggest that understanding how snakes accomplish
these tremendous feats could hold vital clues for the development of treatments
for many different types of human diseases.

"The Burmese python has an amazing physiology. With its genome in
hand, we can now explore the many untapped molecular mechanisms it uses to
dramatically increase metabolic rate, to shut down acid production, to improve
intestinal function, and to rapidly increase the size of its heart, intestine,
pancreas, liver, and kidneys," said Stephen Secor, associate professor of
biological sciences at the University of Alabama and a co-author on the paper.
'The benefits of these discoveries transcends to the treatment of metabolic
diseases, ulcers, intestinal malabsorption, Crohn's disease, cardiac
hypertrophy and the loss of organ performance."

To complete their work, the research team aligned 7,442 genes from the
python and cobra with genes sequences available in the Ensembl Genome Browser
from other amphibians, reptile, bird and mammals. They used a statistical
method called "branch site codon modeling" to look for genes that had
been positively selected (or evolutionarily changed due to natural selection)
in the python, the cobra, and early in snake evolution in the common ancestor
of these two snakes. They found changes in hundreds of genes. They believe the
results demonstrate that natural selection-driven changes in many genes that
encode proteins contributed substantially to the unique characteristics of
snakes.

Analyses showed a remarkable correspondence between the function of the
selected genes, and the many functionally unique aspects of snake biology --
such as their unique metabolism, spine and skull shape and cell cycle
regulation, Castoe said. Many of the altered genes the team observed also have
prominent medical significance. For example, the python genome showed some
changes to the gene GAB1, which other research suggests plays a role in breast
cancer, melanomas and childhood leukemia.

In addition to changes to individual genes and their expression,
researchers also found that the extreme characteristics in snakes could also be
linked to duplications or losses in multigene families. Some of those include
ancient loss and more recent re-evolution of high resolution vision, and their
ability to detect chemical cues from the environment. Researchers also observed
that, while most assume that reptile genes and genomes change at a very slow
rate, snake genomes evolve at one of the fastest rates of any vertebrate.







Story Source:

The above story is based on materials provided
by University of Texas at Arlington. Note:
Materials may be edited for content and length.







Journal Reference:

1.   
Todd A. Castoe, A. P. Jason de Koning, Kathryn T. Hall, Daren C. Card, Drew
R. Schield, Matthew K. Fujita, Robert P. Ruggiero, Jack F. Degner, Juan M.
Daza, Wanjun Gu, Jacobo Reyes-Velasco, Kyle J. Shaney, Jill M. Castoe, Samuel
E. Fox, Alex W. Poole, Daniel Polanco, Jason Dobry, Michael W. Vandewege, Qing
Li, Ryan K. Schott, Aurélie Kapusta, Patrick Minx, Cédric Feschotte, Peter
Uetz, David A. Ray, Federico G. Hoffmann, Robert Bogden, Eric N. Smith, Belinda
S. W. Chang, Freek J. Vonk, Nicholas R. Casewell, Christiaan V. Henkel, Michael
K. Richardson, Stephen P. Mackessy, Anne M. Bronikowsi, Mark Yandell, Wesley C.
Warren, Stephen M. Secor, and David D. Pollock.The Burmese python genome
reveals the molecular basis for extreme adaptation in snakes. PNAS,
December 2, 2013 DOI: 10.1073/pnas.1314475110

http://www.sciencedaily.com/releases/2013/12/131202162117.htm

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