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later contributed to the evolution of claws in reptiles and
feathers in birds.
In turtles, many of the EDC genes have evolved to
code for proteins that can be efficiently cross-linked to
harden the skin component of the shell. Moreover, betakeratin genes within and outside of the EDC have acquired specific expression in the scutes of the turtle
shell. Molecular phylogenetic analyses lead the authors
to hypothesize that these specialized shell beta-keratins
have evolved from components of the hard claws in
primitive reptiles.
Remarkably, the basic organization of the EDC gene
cluster is shared between turtles and humans due to inheritance from a common ancestor that lived approximately 310 Ma. Previous studies have suggested that
EDC genes protect against the entry of allergens and
microbes through the human skin. The newly published
report demonstrates that evolutionary-related genes
contribute to the defense against environmental insults
in both humans and turtles.
Reference
Holthaus KB, Strasser B, Sipos W, Mlitz V, Weissenbacher A, Tschachler
E, Alibardi L, Eckhart L. 2016. Comparative genomics identifies
epidermal proteins associated with the evolution of the turtle
shell. Mol Biol Evol. 33:726–737.
Joseph Caspermeyer*,1
1
MBE Press Office
*Corresponding author: E-mail: [email protected].
doi:10.1093/molbev/msv277
Advance Access publication December 31, 2015
The South American Origins and Spread of the Irish Potato
Famine Pathogen
Using some ancient DNA detective work, a new study led by
University of California Berkeley postdoctoral researcher Mike
D. Martin and University of Copenhagen professor Tom
Gilbert has linked the culprit behind the 19th-century Irish
potato famine, which was transported to Europe in the 1840s,
to a fungus-like organism that originated in South America.
Just how the pathogen, called Phytophthora infestans,
made the transatlantic leap to destroy potato crops on
a global scale is a “Guns, Germs, and Steel”-like tale of
New World exploration and devastation published in the
advanced online edition of Molecular Biology and
Evolution.
The authors used genome sequences from 71 modern and
historical samples of the microbial pathogen, a unique collection culled from worldwide private archives, to construct the
ancestral tree of the pathogen. The origin of the species dates
back to 1558 AD, the age when the first Europeans explored
South America.
The research team further observed that the species was
first introduced to 19th-century Europe shortly after it evolved
and diversified. They found a close connection between a
present-day sister species, P. andina (found only in the highlands of Ecuador and Peru) and the ancient P. infestans that
triggered the first global outbreak in 1845 and the catastrophic Irish potato famine.
The authors speculate that after being found in South
America, the pathogen either spread from South America
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directly to the United States or was simultaneously introduced from Mexico into South America and the United
States prior to its infestation of Europe. “We think early
European activities in the New World led to the origin of
this devastating pathogen. Countless improbable events led
to the introduction of this species to Europe in 1845, but our
work narrows down the evolutionary possibilities to exactly
two,” said Martin et al. (2015).
Future work will try to trace the exact route into Europe.
“Ultimately finding the precise location where this species
evolved could lead potato breeders to discover new genetic
tools for improving resistance against potato blight disease,”
said Martin et al. (2015).
Reference
Martin MD, Vieira FG, Ho SYW, Wales N, Schubert M, Seguin-Orlando
A, Ristaino JB, Gilbert MTP. 2016. Genomic characterization of a
South American Phytophthora hybrid mandates reassessment of
the geographic origins of Phytophthora infestans. Mol Biol Evol.
33:478–491.
Joseph Caspermeyer*,1
1
MBE Press Office
*Corresponding author: E-mail: [email protected].
doi:10.1093/molbev/msv278
Advance Access publication December 29, 2015