FOR RELEASE: June 25, 1997
Contact: Blaine P. Friedlander, Jr.
Office: (607) 255-3290
Internet: [email protected]
Compuserve: Larry Bernard 72650,565
http://www.news.cornell.edu
ITHACA, N.Y. -- In the ongoing bout with plant pests, scientists at the
Boyce Thompson Institute for Plant Research Inc., located at Cornell
University, have found a one-two punch. The researchers have discovered
and cloned a protein that, when delivered into an insect's gut by way of a
"trojan horse," attacks the pest's intestines, rendering the pest helpless
against a companion virus.
"No one has really studied the biochemistry and molecular biology of an
insect's peritrophic matrix before," said Robert R. Granados, the Charles
E. Palm Distinguished Scientist and virologist at Boyce Thompson Institute
(BTI) and Cornell adjunct professor of entomology. "In our opinion, the
peritrophic matrix (PM -- the interior lining of the insect's intestine,)
is an important component in the insect's immune system against biological
control agents. We've finally defined the site of the action of enhancin
on the peritrophic matrix." Enhancin binds to a major mucinous protein of
peritrophic matrix, destroying the matrix structure, thus allowing the
baculovirus to pass through this relatively impermeable matrix unimpeded
where it can kill the host, Granados explained.
Granados and colleagues reported their findings, "An intestinal mucin is
the target substrate for a baculovirus enhancin," in Proceedings of the
National Academy of Sciences (24 June 1997), authored by Granados and Ping
Wang, Cornell graduate student in entomology. Another research report,
"Molecular cloning and sequencing of a novel invertebrate intestinal mucin
cDNA," is scheduled for publication in the Journal of Biological Chemistry
(27 June 1997), authored by Wang and Granados.
The mucinous peritrophic matrix, the inside lining of the insect's
intestine, is made mostly of chitin and proteins. It was previously
believed that the insects' peritrophic matrix provided a barrier against
certain microbial attack. What this discovery allows: the enhancin (an
enzyme), when consumed by the insect, will break down the mucinous
component of the peritrophic matrix, facilitating the passage of a virus,
and resulting in the rapid death of the insect. "Mucins from mammals have
been extensively studied," Granados said. "In contrast, knowledge about
invertebrate mucins is very limited."
Wang and Granados discovered and cloned the first invertebrate intestinal
mucin gene from the cabbage looper larvae (Trichoplusia ni). The
researchers looked at seven types of pests and found their method to be
effective against the fall armyworm, beet armyworm, the cotton bollworm,
the American budworm, the velvetbean caterpillar and the common armyworm.
In the future, growers may use polyhedron crystals -- which contain
enhancin and a pest-specific baculovirus. A pesky caterpillar, for
example, will eat part of a leaf containing the polyhedron. The crystal
would be dissolved in the insect's intestines, releasing the gut-wrenching
enhancin and the baculovirus simultaneously. Neither the protein nor the
baculovirus will harm humans or animals, Granados said. Acidity in human
stomachs and intestines renders the protein ineffective against
vertebrates. Invertebrate species -- such an insects -- do not have highly
acidic intestinal contents.
The BTI researchers are seeking to genetically engineer the enhancin gene
into plants, where it has considerable potential, Granados said.
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