GENET archive


SCIENCE: Recent GE research news

                                 PART I
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TITLE:  Silkworms spin a rainbow
SOURCE: Australian Broadcasting Corporation, Australia
AUTHOR: Agenše France-Presse
DATE:   09.05.2007

Silkworms spin a rainbow

Why take all the trouble to dye silk when silkworms can be genetically
modified to spin any colour of the rainbow? That's the goal of Japanese
scientists who have genetically engineered silkworms to produce a
specific colour, according to a study published this week in the
Proceedings of the National Academy of Sciences. Lead author Takashi
Sakudoh, of the University of Tokyo, says understanding the pigment
transport system of silkworms could "pave the way for genetic
manipulation of the colour and pigment content of silk". For starters,
the researchers have produced silkworms that make yellow silk. But they
say that in the future, the worms could be manipulated to produce flesh-
coloured or reddish silk. In nature, silkworm cocoon colours vary from
white, yellow, straw, salmon, pink to green. The colours in the silk are
from natural pigments absorbed when the silkworms eat mulberry leaves.
And the genetics behind this ability to extract natural pigments is
crucial, the scientists say. For instance, a gene known as 'yellow
blood' or Y gene enables silkworms to extract carotenoids, yellow-
coloured compounds, from mulberry leaves. And worms that have a mutated
Y gene, where a segment of DNA is deleted, cannot do this so produce
white silk. Insects with this mutation produce a non-functional form of
the carotenoid-binding protein (CBP), known to aid pigment uptake. Using
genetic engineering techniques, the researchers introduced pristine Y
genes into the mutant insects. The engineered worms produced working CBP
and yellow-coloured cocoons. The yellow colour became more vivid after
rounds of crossbreeding, the researchers say.

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                                 PART II
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TITLE:  Beer helps scientists find landmines
SOURCE: Australian Broadcasting Corporation, Australia
AUTHOR: Agenše France-Presse
DATE:   08.05.2007

Beer helps scientists find landmines

Biotechnologists have genetically engineered brewer's yeast to glow
green in response to an ingredient found in landmines, a new study
shows. The study, published today online in the journal Nature Chemical
Biology, shows the yeast can detect, or smell, airborne particles from
explosives. The scientists engineered the yeast Saccharomyces cerevisiae
to sense molecules of the chemical DNT, or dinitrotoluene. DNT is left
over after making the explosive TNT, or trinitroluene. And dogs trained
to sniff for explosives are believed in fact to be trained to detect
DNT. The scientists spliced a gene found in rats into the yeast's genome
so that the surface of its cells reacted in response to DNT. To get a
visual cue as to whether this 'nose' had detected DNT, the scientists
also added a gene to turn the yeast a fluorescent green when contact was
made. The authors, led by Associate Professor Danny Dhanasekaran of
Temple University School of Medicine in Philadelphia, believe they have
found a useful, if so far experimental, type of biosensor. These gadgets
use organisms to detect environmental chemicals, including biological or
chemical weapons. In the past, scientists have shown that organisms such
as moths and bees can detect explosives.

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                                 PART III
------------------------------- GENET-news -------------------------------
TITLE:  Engineering bacteria to harvest light
SOURCE: MIT Technology Review, USA
AUTHOR: Emily Singer
DATE:   26.03.2007

Engineering bacteria to harvest light

A set of genes found in marine microorganisms can endow common bacteria
with the ability to generate energy from light.

Commonly used lab bacteria called E. coli can be converted into light-
harvesting organisms in a single genetic step, according to new research
from MIT. The genetic enhancement allows microorganisms that normally
derive their cellular energy from sugars to switch to a diet of
sunlight. These findings could ultimately be used to genetically
engineer bacteria that can more efficiently produce biofuels, drugs, and
other chemicals.

Some bacteria, such as cyanobacteria, use photosynthesis to make sugars,
just as plants do. But others have a newly discovered ability to harvest
light through a different mechanism: using light-activated proteins
known as proteorhodopsins, which are similar to proteins found in our
retinas. When the protein is bound to a light-sensitive molecule called
retinal and hit with light, it pumps positively charged protons across
the cell membrane. That creates an electrical gradient that acts as a
source of energy, much like the voltage, or electromotive force,
supplied by batteries.

First discovered in marine organisms in 2000, scientists recently found
that the genes for the proteorhodopsin system--essentially a genetic
module that includes the genes that code for both the protein and the
enzymes required to produce retinal--are frequently swapped among
different microorganisms in the ocean. (While we usually think of genes
being passed from parent to offspring, microorganisms can exchange bits
of DNA laterally.)

Intrigued by the prospect that a single piece of DNA is really all an
organism needs to harvest energy from light, the researchers inserted it
into E. coli. They found that the microorganisms synthesized all the
necessary components and assembled them in the cell membrane, using the
system to generate energy. "All it takes to derive energy from sunlight
is that bit of DNA," saysEd Delong, professor of biological engineering
at MIT and author of the study. The results were published last week in
the Proceedings of the National Academy of Sciences.

The findings have implications for both marine ecology and for synthetic
biology, an emerging field that aims to design and build new life forms
that can perform useful functions. Giant genomic studies of the ocean
have found that the rhodopsin system is surprisingly widespread. The
fact that a single gene transfer can result in an entirely new
functionality helps explain how this genetic module traveled so widely.
In fact for microbes, this kind of module swapping may be the rule
rather than the exception."A new paradigm is emerging in microbiology:
[microorganisms] are much more fluid than we thought," says Ford
Doolittle, Canada Research Chair in comparative genomics at
DalhousieUniversity, in Nova Scotia.

These findings and other research on proteorhodopsins could provide
biological engineers with a new tool to tinker with.A paper published
last month by Jan Liphardt and colleagues at the University of
California, Berkeley, showed that E. coli engineered to have a
proteorhodopsin pump can easily switch between energy sources: when
bacteria are starved of their regular energy supply, they use light
energy to drive their flagellar motor, a rotating tail that bacteria use
to swim. The more light there is, the faster the motor goes.

Rhodopsin pumps could eventually be engineered into the microbes
commonly used to produce drugs and other chemicals. These bacterial
factories sometimes run short on energy. "Using these light-driven
proton pumps, bacteria can be energized by light to increase their
yields of metabolites or pharmacologically active substances," says John
L. Spudich, professor of microbiology and molecular genetics at the
University of Texas Medical School, in Houston. A cellular energy boost
might come in particularly handy with the latest trend in bacterial
production: engineering microbes to produce biofuels.

"It's sort of like creating a hybrid car," says MIT's Delong. "Instead
of supplementing gas with energy stored in a battery, cells can
supplement their energy metabolism with light."

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