Afifa hameed

Roll no 11011514-031

Sec G

Entomology

UOG

Transgenic plants for insect

resistance (review)

authors: Lise Jouanin, Michel Bonade´-

Bottino , Ce´cile Girard , Gil Morrot ,Marc

Giband(2007)

journal: Elsevier science

,

Received 11 September 2006

revised 17 October

accepted 20 October 2007

Volume 72

abstract

Genetic engineering insect resistance

plants

Two approaches in this paper

1st…delta endotoxin sequence of gene from

B. thuringensis

2nd ..plant derived genes……enzymes

inhibitors and lectins.

introduction Loss of agriculture 37% pest and

dieases.

13% insects

Use of chemicals is harmful for plants and also for other animals and birds..

Future planning ……environment friendly methods of insect resistance by breeding techniques.e.g somatic hybrid potato have resistance against potato beetle..

( J. Cheng et all,2002)

Delta endotoxin from B.thuringensis…

1996 first time insecticidal plant in market.

1) Use of Bacillus thuringiensis d-endotoxins

The B. thuringiensis toxins: first discover from silkworm population….1902 (Japan)

1911 from flour moth population..(Germany)

They are gram +ve bacteria produced crystalline inclusion during sporulation.

Crystalline inclusion…………delta endotoxin….

Several crystalline proteins formed by B.thuringenisis ..

90 genes isolated from it that form protoxin..

(M. Mazier et all 2002)

First identify proteins cryI, cryII, cryIII….host

specific

E.g cry I……Lepidoptera

Cry II……..coleoptera

(H.R. Whiteley,2000)

Delta endotoxin solublized insect mid gut,

activate by gut proteases..cleave protein into

smaller polypeptide(toxin)….toxin binds to

epithelial surface of gut cells and destroys cells

and insect dia.

(B.H. Knowles et all, 2003)

Transgenic plants Safe method….entire plant protect from insects and those

parts where spray not reached.

First transfer of B.thuringensis genes in

tobacco,tomato,1987..

Then cotton, maize, rice ……..Lepidoptera as main target.

(M. Vaeck et all,2003)

Several proteins constructed as

cryIA(a),cryIA(b),cryIa(c)… for lepidoptera.

cryIC,cryIIIA…..coleoptera e.g (colorado potato beetle)

( F.J. Perlak,2001)

First field trial of expressing this bacterial gene in 1986 with tobacco on small scale then on large scale in US. (A.F. Krattiger et

all,2005)1995 the first transgenic crops cryIA(b) toxin

expressed in corn.Cotton cryA( c) Potato cryIIIA1996…..1.2 million ha B.thuringensis

transgenic crops in US. (M. Peferoen et all,2004)

New methods of screening (antibody PCR) now used for more identification of toxin in B.turingensis..

2) Use of plant-derived genes

Plants derived proteins protects plants

from insect attack..importantly protect

from those insect that attack on

vulnerable parts as seeds.

Different proteins as proteases

inhibitors ,lectins interfere with growth

and development of larvae of insects

and cause death of them.

(C.A. Ryan,2000)

Proteinase inhibitors

4 types….inhibiting serine,cystein,metallo or aspartyl proteases.

Protease inhibitor small size…serine has two active sites….trypsin…chymotrypsin …

(G.R. Reeck et all,2002)

Serine is abundant in seeds and storage tissues.

PI..interfere with insect larval growth.

First transgenic gene isolated from cowpea encoded for trypsin/ trypsin inhibitor CPTI (protein against field and storage pests).

Plant resistance against lepidoptera…….serine PI originate from different sources..

Fewer cysteins are known and their action on insects.

Gene encoding a cystein PI isolated from rice introduced in tobacco,potato,poplar,oil seed rape and cotto.only result of toxicity against beetle feeding on poplar.

(J.C. Leple et all 2005)

Some insects now have resistance against PI so new methods and techniques trying to find for this problem.

a-Amylase inhibitors

Common bean Phaseolus vulgaris (kidney

bean) have seed protein PHA.E and L

arcelin and a.amylase (a.AI).

PHA.E and L arcelin are

lectins…..agglutinin activity.

a.amylase defense against insects.

A.amylase from common bean

resistance to bruchid beetle

(Bruchus pisorum).

Transfer of a.amylase gene to azuki

bean protect it from 3 species of

bruchids.

Drawback: in nature Acnathoscelides

obtectus and Zabrotes subfasciatus feed

on those plants that produced

a.amylase.having serine proteases that

able to cleave a.amylase..

(M. Ishimoto,1996)

Lectins

Carbohydrate binding proteins….in seeds and

storage tissues.

Toxic to birds and mammals to some extent.

Toxicity against insects have been observed.

however exact mechanism not known . (T.M. Czapla et all,2003)

Lectins bind to glycoconjugates located in mid

gut of insects.

Lectins from garlic and snowdrop are toxic to

insects.

Tobacco plants expressing a pea lectin were

shown to be toxic to the Lepidoptera Heliothis

virescens..

potato plants expressing the snowdrop lectin

(GNA) were toxic to the Lepidoptera Lacanobia

oleracea.

Most work involving lectins has

focused on the obtention of aphid-resistant

plants.

The expression of the GNA in tobacco resulted

in

added protection against the aphid Myzus

persicae

(V.A. Hilder et all.2000)

Myzus persicae

Heliothis

virescens..

Chitinases

Alkaloids…..antifeedant to insects

Tryptophan decarboxylase from Catharanthus

roseus allows the synthesis of tryptamine and

tryptamine-based alkaloids in tobacco caused

the death of whitefly pupae.

(J.C. Thomas et all,2000)

The expression of a bean chitinase in potato

causes no deleterious effect to a Lepidoptera,

Lacanobia oleracea, but reduces fecondity of

the aphid A. solani.

(A.M.R. Gatehouse)

New insecticidal genes

Struggle for identification of new insecticidal

products.

Usually plant samples…….tropical plants and

bacteria of different physiology stages.

B.thuringensis produced a protein Vip3A against

Lepidoptera e.g. cutworms (corn pest).

(J.J. Estruch et all,2003)

Streptomyces secretes cholesterol oxydase

against boll weevil.

(H.-J. Cho et all,2005)

These are new interesting sources for engineering

resistance.

conclusions: Engineering crops with insecticidal protein genes

is one of first major projects in plant biotechnology.

The value of such technology to the Seed biotechnology industry, the farmer, the environment and the consumer is obvious.

Insect-resistant

crops could reduce the cost, time and

efforts spent protecting crops from insects.

Environment friendly…

Continuing

research on new sources of resistance is essential

for the long term control of insect pests.

Continuing research on new sources of resistance is essential for the long term control of insect pests.

In a first step, studies on the expression and potential of the new insecticidal genes can be performed in model plants such as tobacco.

In a second step, the selected gene(s) must be introduced into the target crop.

In another step, field trials must be performed in different locations and for several years.

(M.O. Santos et all,2006)