Same Tools, Different Boxes
Convergent evolution plays out in plant and animal innate immunity
By Philip Hunter

As life's diversity demonstrates, nature has a pretty large toolbox for
designing adaptations. While in many ways an efficient builder, it often
reuses blueprints, even if not starting with the same tools. Analogous wing
structures in bird and bat suggest a why-mess-with-success ethos. New World
cacti and desert-dwelling Euphorbiaceae in the Old World share protective
spines and photosynthesizing stems even though the last common ancestor
predates such modifications.

Beyond structural adaptations, researchers are investigating convergent
evolution at the molecular level, and this may allow for broader comparisons
even between plants and animals. Both, of course, share the building blocks
and fundamental biochemistry that evolved before the two kingdoms presumably
diverged from common single-celled ancestors. But with their radically
different cell structures, plants and animals were thought to have pursued
largely independent evolutionary routes. Such disparity was reflected in the
lack of interaction between the respective research communities.

But much is changing, especially with respect to the study of innate
immunity, which turns out to involve strikingly similar mechanisms in both
plants and animals. One can find resemblances in the receptors that
recognize pathogenic components such as lipopolysaccharide; in the signaling
systems that initiate responses through kinase cascades; and in the defense
mechanisms, including reactive molecules such as nitric oxide, says Jonathan
Jones, senior scientist at the Sainsbury Laboratory of the John Innes Centre
in Norwich, UK.

Moreover, says Jones, autoimmune disorders can develop in plants as well as
animals. In many cases, researchers consider plant and animal
innate-immunity analogs to have evolved independently, because the
underlying genes involved are radically different. Here, convergence is
occurring purely at the functional level, according to Daniel Klessig,
president and CEO of Boyce Thompson Institute (BTI) for Plant Research in
Ithaca, NY. But now, say some, both functional and genetic similarities
between plant and animal immunity are leading to cross-pollination between
the respective research fields.

Read the rest at TheScientist.com
http://www.the-scientist.com/yr2004/feb/research4_040216.html

Comment:
Could viral vectors be suspected here?


When the Lights Went On for COP9
A protein's role in ubiquitin-mediated proteasomal degradation plants the
seed for big ideas
By Eugene Russo

It doesn't take a green thumb to predict what happens to plants left in the
dark: They wither. But in the late 1980s and early 1990s, researchers,
including people in Xing-Wang Deng's Yale University lab, stumbled upon a
group of intriguing Arabidopsis mutants that seemed to defy intuition. If
provided the right nutrition, these plants could retain a shape, form, and
cellular state similar to those grown in ample light for weeks, and even
months, of sustained darkness. Some could even flower.

In 1994, Deng's group identified COP9, one of the genes responsible for this
impressive feat.1 After doing some bioinformatics digging and biochemistry
work, they found that the COP9 gene encoded a novel protein that was part of
a larger protein complex later called the COP9 signalosome (CSN).

As it turns out, the CSN does more than regulate plant responses to light;
Deng's lab and others subsequently found signalosome homologs in mammals and
other species. "There were a variety of different facts floating around and
a lot of speculation," says Svetlana Lyapina, a Hot Paper first author and
now a manager of strategy and corporate development at Amgen, Thousand Oaks,
Calif. "But there was no sort of unified theory of what signalosome does and
how it does it."

This issue's Hot Papers2,3 link CSN function to ubiquitin ligases, a family
that includes hundreds of known key regulators of inflammation and the cell
cycle. Approaching signalosome function from different fields (biochemistry
and plant genetics) and with different agendas, the two groups found that in
plants,2 yeast, and mammalian cells,3 the CSN directly interacts with an
ubiquitin ligase complex that mediates proteasomal degradation of proteins
involved in cell cycle and development.

"Basically, this provided a biochemical mechanism, a biochemical connection
for how COP9 signalosome is involved in protein degradation mediated by the
proteasome," says Deng. The complexes are now known to be major signaling
processors in the cell, and they may be relevant in treating diseases such
as cancer. Thus, with the shade drawn, a new research window had burst open.

http://www.the-scientist.com/yr2004/feb/hot_040216.html

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