Columbia, Missouri
May 15, 2007COLUMBIA,
Mo. - A team of scientists at the
University of
Missouri-Columbia (MU) has discovered a way to create
engineered minichromosomes in maize and attach genes to those
minichromosomes. This discovery opens new possibilities for the
development of crops that are multiply resistant to viruses,
insects, fungi, bacteria and herbicides, and for the development
of proteins and metabolites that can be used to treat human
illnesses.
In a paper published in the
Proceedings of the National
Academy of Sciences (PNAS), Weichang Yu, Fangpu Han, Zhi
Gao, Juan M. Vega and James A. Birchler built on a previous MU
discovery about the creation of minichromosomes to demonstrate
that genes could be stacked on the minichromosomes.
“This has been sought for a
long time in the plant world, and it should open many new
avenues. If we can do this in plants, many advances could be
done in agriculture that would not otherwise be possible, from
improved crops to inexpensive pharmaceutical production to other
applications in biotechnology,” said Birchler, professor of
biological sciences in the MU College of Arts and Science.
A minichromosome is an
extremely small version of a chromosome, the threadlike linear
strand of DNA and associated proteins that carry genes and
functions in the transmission of hereditary information. Whereas
a chromosome is made of both centromeres and telomeres with much
intervening DNA, a minichromosome contains only centromeres and
telomeres, the end section of a chromosome, with little else.
However, minichromosomes have the ability to accept the addition
of new genes in subsequent experiments.
Birchler said there have been
unsuccessful efforts to create artificial chromosomes in plants
but this is the first time engineered minichromosomes have been
made. Minichromosomes are able to function in many of the same
ways as chromosomes but allow for genes to be stacked on them.
Although other forms of genetic modification in plants are
currently utilized, the new minichromosomes are particularly
useful because they allow scientists to add numerous genes onto
one minichromosome and manipulate those genes easily because
they are all in one place, Birchler said. Genetic modification
with traditional methods is more complicated because scientists
have little control over where the genes are located in the
chromosomes and cannot stack multiple genes on a separate
chromosome independent of the others.
By stacking genes on
minichromosomes, scientists could create crops that have
multiple beneficial traits, such as resistance to drought,
certain viruses and insects, or other stresses. In addition,
minichromosomes could be used for the inexpensive production of
multiple foreign proteins and metabolites useful for medical
purposes. Because of their protein-rich composition, a part of
the maize kernels (called an endosperm) can be used to grow
animal proteins and human antibodies that treat diseases and
disease symptoms. Minichromosomes could enable new and better
production of these foreign proteins and antibodies. In
addition, scientists also may be able to use them to develop
plants better suited for biofuel production.
“The technique used to create
our engineered minichromosomes should be transferable to other
plant species,” Birchler said.
He said he hopes that he and
other scientists can use the technique to create minichromosomes
in other plant varieties and produce more resistant plant
strains, develop more medically useful proteins and metabolites,
and study how chromosomes function. |
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