investigation of bacillus thuringiensis cry1aa toxicity to ephestia kuehniella
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Laboratoire de protection et amélioration des plantes ******************** Equipe des biopesticides. Centre de Biotechnologie de Sfax. Investigation of Bacillus thuringiensis Cry1Aa toxicity to Ephestia kuehniella ( Lepidoptera : Pyralidae ). - PowerPoint PPT PresentationTRANSCRIPT
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Investigation of Bacillus thuringiensis Cry1Aa
toxicity to Ephestia kuehniella
(Lepidoptera: Pyralidae)
Souad Rouis, Maissa Chakroun, Nouha Abdelmalek and Slim Tounsi
CENTRE DE BIOTECHNOLOGIE DE SFAX LABORATOIRE DE PROTECTION ET AMÉLIORATION DES PLANTES
********************EQUIPE DES BIOPESTICIDES
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Bacillus thuringiensis
spore-forming bacteria
Each crystal is formed by one or more -endotoxins (cry proteins) that define the nature of the spectrum insecticidal activity
Products crystals during the sporulation phase
cristal
spore
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δ-endotoxins Structure
• 3 domains:Domain I: 7 α helicesDomain II: 3 β antiparallel feuilletsDomain III: 2 β antiparallel feuillets
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-endotoxins Domains specificity
Model Umbrella
It probably interacts with
membrane receptors of the intestinal cells
Role is not clear???
It is supposed to penetrate to the
BBM?
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Solubilisation
Solubilisation
Activation
Activation
Active ToxineActive Toxine
BindingBinding
Midgut
receptors
Ingestion
Ingestion
Oligomerization et
perforation
Oligomerization et
perforation
Insect deathInsect death
Mode of action of -endotoxins
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Activation by proteolysis : Basal Membrane : Latéral Membrane: Apical Membrane
Toxin-receptor interaction
The toxin creates pores in the membrane of apical microvilli
Exchange between the intra and extra cellular environment
Changes of cell morphology
Death of the insect
Mode of action of -endotoxins
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Cry1Aa protein
• Molecular Mass : 130 kDa.• Cry1Aa of BNS3 : Inactive against The
flour moth Ephestia kuehniella (Lepidoptera)
Cry1Ab Cry1Ac Cry1Ba Cry1Ca Cry1Da Cry3A Cry4A Cry4B Cry4C
Cry1Aa 90 82 55 67 71 25 27 27
22
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Previous work conducted in our laboratory has shown that, unlike the δ-endotoxin Cry1Ac, Cry1Aa shows no toxicity towards E. kuehniella even at high concentrations (Tounsi et al., 2005)
However, it has been reported in the literature that Cry1Aa is seven times more toxic than Cry1Ac on Bombyx Mori (Wolfersberger, M 1996)
BNS3 strain expressing toxins (Cry1Aa, Cry1Ac and Cry2), was isolated and characterized in our laboratory (Jaoua et al., 2000)
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Impact of the difference of Cry1Aa and Cry1Ac structure on their susceptibility to activation
and / or inactivation by proteolysis
(a) protoxins Cry1Ac and Cry1Aa digested by
proteases of the gut juice of E.kuehniella T: protoxins of Cry1Ac and Cry1Aa
(b) protoxins of Cry1Ac and Cry1Aa digested by the
chymotrypsin
Various potential sites for digestion by chymotrypsin
Cry1Ac is fully activated by the proteases of the gut juice of E. kuehniella
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Comparative study by zymogramme of proteases of the gut juice of E. kuehniella involved in the activation of
both toxinsThe protease activity of the juice of E. kuehniella (L3) against Cry1Ac involves two additional proteases
This difference in protease activity could contribute to a relative resistance of E. kuehniella towards Cry1Aa
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Cry 1Aa Cry 1Ac
5 544 332 211
31 kDa
14,4 kDa
66,2 kDa45 kDa
20 kDa
6,5 kDa
C+ C+
Hybridization with anti-Cry1Aa
1 5: decreasing concentrations of Pronase
Comparative study of the susceptibility of the two toxins Cry1Aa and Cry1Ac to digestion
by PronaseThe Pronase is a mixture of different types of proteases, serine proteases, metalloproteases, carboxypeptidases, aminopeptidases, chymotrypsin, trypsin
« Exfashion » Activity : prediction of differences in conformation
Cry1Ac is more resistant to Pronase, suggesting a difference in conformation
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Marqueur de taille
66,2 kDa 45 kDa 31 kDa 20 kDa
14,4 kDa 6,5 kDa
15 4 3 2 15 4 3 2 C+C+
Cry1Ac Cry1Aa
Western Blot
Cry1Ac 4-5 peptide is more resistant to pronase than Cry1Aa one
1- additional cleavage site in Cry1Aa ?
2- conformational change to protect a cleavage site in Cry1Ac
Comparative study of the susceptibility of Cry1Aa and Cry1Ac
a4-5 domains to digestion by Pronase
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Cry 1AaCry1Ac
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Lumen (Lu); membrane Apicale (Am); membrane Basale (Bm); grossissement 100x
control Cry 1Aa Cry1Ac
Histopathological effects of the interaction between Cry1Aa and
Cry1Ac with receptors on the intestinal cells of E. kuehniella
Hypertrophy of Epithelial cells
Complete disintegration of the epithelial cells
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Lumen (Lu); membrane Apicale (Am); membrane Basale (Bm);Magnification 100x
controle Cry1AcCry1Aa
Immunohistochemical localization of the toxins Cry1Aa and Cry1Ac in the intestine of E.
kuehniella
Clear localization of the toxin Cry1Ac in
the basal membrane of
epithelial cells.
Slight localization of the toxin Cry1Aa in the
apical membrane of epithelial cells
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Comparative study « in vitro » of the interaction between the
toxins Cry1Aa, Cry1Ac and the receptors of E. kuehniella
Cry1Ac binds to a number of receptors more important than Cry1Aa
The intensity of the bands observed in the case of Cry1Ac suggests the presence of a large number of receptors and / or a greater affinity towards the same receptors that Cry1Aa
BSA
BBMV
100
kDa
10080
kDa
BBMV BBMV
Cry1Ac Cry1Aa
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Cry1Aa CL50 (g/g of semolina)
Stage L1 429,048±123,28
Stage L5 1420.483 ±594.794
Positive control CL50 (g/g of semolina)
Stage L1 76,148±28,341
Stage L5 90,188±27,308
For Cry1Aa, the difference is clear between L1 and L5 larvea stages
Comparative toxicity assay of recombinant strain harboring cry1Aa gene againt Ephestia
kuehniella larvea
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Stage L5
ON 5h 3h 2h 1h ND M ND 1h 2h 3h 5h ON
Stage L1
ON 5h 3h 2h 1h ND M ND 1h 2h 3h 5h ON
BLB1
BBP4
Positive control
Cry1Aa
60 kDa
The battery of proteases, that the insect has, is apparently different from a larval stage to another.
Positive control Cry1Aa
Comparative study of the susceptibility of recombinant Cry1Aa to Ephestia kuehniella
midgut juce
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45 kDa
97 kDa
66 kDa
A clear difference between proteases batteries of 1st and 5th instar E.kuehniella larvea gut juice
Comparative study of proteases of 1st and 5th instar E.kuehniella
larvea gut juice by zymogramme Positive control Cry1Aa casein
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Receptor Investigation of 1st and 5th instar E. kuehniella larvea
Different receptor profiles between L1 and L5 stages suggesting differences in toxin receptor interaction
M L5 L1 L5 L1
Anti APN1 Anti APN2
SDS PAGE
Western Blot
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L1Negative Control
Comparative histopathological effects of Cry1Aa on 1st and 5th
instar E. kuehniella larvea
L5
Hypertrophy of Epithelial cells
Apparent disintegration of the epithelial cells
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Thank you
شك را