Scope of Genetic Engineered Microbes and Parasitoids in Biological Control

Ph. D. Scholar
Department of Entomology
Indira Gandhi Krishi Vishwavidyalaya
Raipur (Chhattisgarh)

1. SCOPE OF GENETIC ENGINEERED MICROBES AND PARASITOIDS IN BIOLOGICAL CONTROL
Prepared By
AaliyaAfroz
Ph. D. Scholar
Dept. of Entomology, IGKV, Raipur

2. GENETIC ENGINEERING OF PREDATORS AND
PARASITOIDS
◦Geneticimprovementofarthropodnaturalenemiestoenhancetheircapacitytocontrolpestshasbeenachievedpreviouslybyartificialselection(BeckendorfandHoy,1985;JohnsonandTabashnik,1994).
◦Anintegratedpestmanagementprogramfeaturingapredatorymitestrainselectedforinsecticideresistancehasbeensuccessfullyimplemented(HeadleyandHoy,1987).
◦However,thedevelopmentofrecombinantDNAtechniqueshasmadeitpossibleoratleastconceivabletotransfergenesspecifyingbeneficialtraitsdirectlytoarthropods(Ashburneretal.,1998;Heilmannetal.,1994;Hoy,1994).

3. Advantages of use of genetic engineering methods for
the improvement of beneficial arthropods over artificial
selection
◦Thegoalofgeneticimprovementcanbeachievedrapidly,withoutthe
generationsofrearingrequiredforclassicalselectionprotocols
◦Ratherthanselectingsolelyfromtheavailablegenepoolofthe
arthropodnaturalenemy,anygenefromanyspeciescanbeused,in
principle,forgeneticimprovement.

4. Predatory Mites and Parasitic Wasps
◦Analternativegenedeliverymethod,
maternalmicroinjection,wasdevelopedto
trans-formthepesticideresistanceinwestern
predatorymite,Metaseiulusoccidentalis
(PresnailandHoy,1992).
◦Maternalmicroinjectionofmitesprovedtobe
easierthanmicroinjectionofmiteeggs.
◦Maternalmicroinjectionwasalsoattempted
withabraconidparasitoidwasp,Cardiochiles
diaphaniae(PresnailandHoy,1996).

6. GENETIC ENGINEERING OF INSECT PATHOGENS
◦Theabilitytoenhancetheinsecticidalpropertiesofeachgroupof
entomopathogensisrelatedtothedegreeofunderstandingofthe
biologyofpathogenicityandtheeaseofgeneticmanipulation.
◦Mostprogresshasbeenmadetowardoptimizationofbaculovirus
insecticidesatthegeneticlevel.Thesequencesofseveralbaculovirus
genomesarenowknown(Ahrensetal.,1997;Ayresetal.,1994;Gomi
etal.,1999)andanalysisofthisinformationhasgreatlyfacilitated
understandingofthebiologyofbaculovirus–hostinteraction.

7. Fungi
◦Thebroadhostrangeofsomeentomopathogenicfungi,suchas
BeauveriabassianaandMetarhiziumanisopliae,isanattractive
characteristicforinsectpestcontrol.
◦ThemolecularandbiochemicalbasesofpathogenicityofM.
anisopliae,whichcausesgreenmuscardinedisease,havebeen
particularlywellstudied(St.Leger,1995;1993).
◦M.anisopliaenormallytakesfrom5to10daystokillahost
insect.Inordertoenhanceinsecticidalefficacy,additional
copiesofthePr1gene,whichencodesasubtilisin-likeprotease
involvedinhostcuticlepenetration,wereengineeredintothe
genomeofM.anisopliae(St.Legeretal.,1996).

9. Nematodes
◦H.bacteriophorawasengineeredtoexpressC.elegansHsp70A
toenhancetoleranceofhightemperatures(Hashmietal.,1998).
◦Engineeringofentomopathogenicnematodescouldpotentially
beusedtoenhancepathogenicity,improveenvironmental
tolerance,andalterhostrangeoncethegeneticbasesforthese
traitshavebeenelucidated(Poinar,1991).

10. Bacteria
◦Newlydiscoveredtoxingroupssuchasthevegetativeinsecticidalproteins(VIPs)
fromB.cereus(Estruchetal.,1996;Yuetal.,1997),andthePhttoxinsfrom
Photorhabdusluminescens(Bowenetal.,1998)usedtoenhancetheinsecticidal
propertiesoftransgenicplantsand/orpathogens,accordingtothesiteofactionof
eachtoxin.
◦ThepathogenicityandhostrangeofBthasbeenimprovedbyusingboth
recombinantandnon-recombinantmeans.
◦Forexample,theplasmidcomplementofaBtstraincanbealteredwithoutuseof
recombinantDNAmethods:ICPgenescanbetransferredbetweenstrainsbya
conjugation-likeprocess.
◦Astrainwithgenerallygoodinsecticidalactivityisidentified,andavariantthathas
lostplasmidswithICPgenesorhasICPgeneswithrelativelypooractivityisused
forincorporationofplasmidswithgenesencodinghighlyinsecticidalICPs.

11. Viruses
◦Thereareavarietyofproteinsandpeptidessuchasinsect
neurotoxinsthatactwithinthehemocoelthatarenotactive
againstaninsectpestbyingestionorbytopicalapplication.
◦Insectvirusessuchasbaculovirusesprovideadeliverysystem
forthesetoxinsintothehemocoeloftheinsect,wheretheyhave
accesstothesiteofaction.
◦Suchtoxinsprovideasecondlineofoffenseagainstthehost
insectinadditiontothevirusitself.Theonlyinsectvirusesthat
havebeenengineeredforenhancedinsecticidalperformance
arethebaculoviruses.

12. Example:
◦Thegenecodingforthepolyhedralenvelopeproteinwasdeletedfrom
AcMNPVandresultedinasix-foldincreaseininfectivityagainstfirst
instar,Trichoplusiani,comparedtothewild-typevirus(Ignoffoetal.,
1995).
◦ToxinsderivedfromBacillusthuringiensishavebeenexpressedinthe
baculovirusexpressionsystem,whichprovidesausefulsupplyoftoxin
forphysio-logicalstudies(Martensetal.,1990,1995;Merryweatheret
al.,1990;Pangetal.,1992).