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Background:
Modern
agriculture faces the challenge of securing the food supply in
an environmentally compatible manner. Weeds, diseases and pests
are among the most serious problems threatening the production
of a successful harvest. The tools at the disposal of the farmer
to combat insects include adapted crop varieties and pest management
programmes. Breeding for insect resistant crop varieties is often
hampered by a lack of resistance alleles present in the germplasm.
The use of chemical insecticides (and pesticides in general) is
coming under increasing criticism, because of potential environmental
problems which may accrue. Biological controls with baculovirus,
bacteria, fungi or parasitic wasps, represent less than 1% of
the chemical insecticide sales and are only applicable in specific
circumstances. Bacillus thuringiensis toxins are now widely used.
However, the major threat to the Bt-plant technology, although
very successful at this moment, is the potential of insect populations
to develop resistance (Van Rie et al., 1995). This is the right
time to proceed with the research to find novel insecticidal toxins
as alternatives for Bt-toxins, as Bt-resistance could become a
major problem.
Objectives:
In
this project we propose to:
1)
study and select signalling insect peptides which enter the hemolymph
upon oral administration;
2)
design and synthesise peptide analogues for improved stability
and gut transition;
3)
improve the already established expression in tomatoes of a synthetic
gene coding for the insect peptide proctolin, and realise the
plant expression of the allatostatin gene;
4)
develop and evaluate transgenic crops expressing insect peptides
which are orally active.
The
resulting insect tolerant crop varieties will contribute to the
effort of developing environmentally friendly, sustainable agriculture.
This goal fits the CAP, promotes plant health, reduces farmers'
inputs and, in general, should be more acceptable to the consumer
than some current practices.
Description:
The
overall goal of the proposed project is to develop a novel way
to control insect pests. The project will assess the feasibility
of protecting crops from insect attacks by expressing naturally
occurring insect signalling peptides in plants. In this project
we propose to explore an alternative approach for generating insect
tolerant crop varieties. Since 1985, insect physiologists have
discovered about 100 different insect signalling peptides. We
have identified a set of such peptides, which we think have the
potential to become a new class of insecticides. These peptides
control different physiological processes, such as inhibition
of ecdysone synthesis, inhibition of juvenile hormone synthesis,
stimulation of cardiac muscle activity, inhibition of gut motility,
etc. The development of insects exposed to such peptides in unphysiological
dosages, or at unusual times, is dramatically disturbed and can
lead to growth inhibition and death. The question is, of course,
whether peptides can survive in the gut environment, pass through
the gut wall, enter the hemolymph and still maintain their biological
activity. A few papers showing that this is indeed the case have
already been published.
Current
situation/results:
Numerous
peptides and analogues have been synthesised and were used in
feeding and injection assays with different insect species. It
could be shown that some peptides were active even following oral
application. This indicates that some neuropeptides withstand
proteolysis in the midgut and are able to penetrate through the
gut into the hemolymph. This could also be followed using tritiated
peptides in in vivo and in vitro experiments. We
also gained important information on the active core of the peptides
and the effects of sequence modifications (shortening, prolongation
etc.) on their biological activity.
Work
was also initiated on the characterisation of proteolytic enzymes
in the hemolymph. Several important peptidases in the gut of different
insect species could be already identified. With the help of 3H-labelled
peptides, we have been able to follow the time course of peptide
degradation in vitro and in vivo and identify most
of the proteolytic fragments.
The
expression of genes encoding selected signalling peptides has
been successful in different plant species. The resulting transgenic
plants were grown and tested for their biological activity. Further
assays using the plant extracts, as well as detection of the produced
peptides by mass spectrometry, are still in progress.
Coordinator
Jeroen
VAN RIE
Aventis
CropScience N.V.
Jozef
Plateaustraat 22
B-9000
Gent
Tel.:
+32 9 235 84 89
Fax:
+32 9 224 06 94
E-mail:
jeroen.vanrie@aventis.com
Partners
- Geoffrey
Mason COAST
University of London
Birkbeck College
Malet Street
UK-WC1E 7HX London
Tel.: +44 1716 31 62 45
Fax: +44 1716 31 62 46
E-mail: g.coast@biol.bbk.ac.uk
- Constantin
POULOS
University of Patras
Dept. of Chemistry
Organic Chemistry, Biochemistry and Natural Products Division
GR-26500 Patras
Tel.: +30 61 99 71 72
Fax: +30 61 99 71 18
E-mail: c.poulos@upatras.gr
- Rosa
RAO
Università degli Studi di Napoli - Frederico II
Dept. of Agronomy and Plant Genetics
Via Universita 100
I-80055 Portici (Napoli)
Tel.: +39 081 77 88 54 44
Fax: +39 081 77 53 579
E-mail: rao@ds.unina.it
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