Engineering Plants for Nematode Resistance

8/3/2019 Engineering Plants for Nematode Resistance

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ENGINEERING PLANTS

FOR NEMATODE

RESISTANCE

Prepared by

ASWINI RAM

II M.Sc., BIOTECHNOLOGY

SREE NARAYANA GURU COLLEGE- COIMBATORE



CONTENTS

INTRODUCTION

FEEDING HABITS OF NEMATODES

MORPHOLOGY OF NEMATODES

SYMPTOMS

STRATEGIES FOR ENGINEERING NEMATODE

RESISTANT PLANTS

RESISTANCE MECHANISMS

CONCLUSION



INTRODUCTION

Nematodes are obligate parasites

Obtain nutrition from plant cytoplasm

Species includes ectoparasites and endoparasites

Sedentary endoparasites of the family Heteroderidae

cause most economic damage

Heteroderidae divided into 2 groups

1) Cyst nematodes 2) Root knot nematodes



FEEDING HABITS OF NEMATODES

Ectoparasitic nematodes

Live completely outside the plant

Migratory endoparasitic nematodes

Live completely inside the plant but move freelybetween the roots and soil

Sedentary endoparasitic nematodes

Live inside the plant but adult female becomes

sedentarySemi- endoparasitic nematodes

Part of body inside root. By movement when feeding



NNMMCMKMCDSKMOMMMORPHOLOGY

DIGESTIVE

ORGANS

REPRODUCTIV

E ORGANS

EXCREATORY

STRUCTURES

MUSCLES

NERVES

TOUGH SKIN

OR CUTICLE



PLANT PARASITIC NEMATODES ALL HAVE

STYLETS (SPEARS) THAT PENETRATE

CELLS AND WITHDRAW THE CONTENTS



SYMPTOMS

Yield loss

Stunting

Yellowing

Water deficiency and wilting

Nutrient deficiency

Direct damage

( knots on roots in potatoes , peanuts.,etc)



CYST NEMATODES ON ROOTES



POTATO ROT NEMATODE



PEANUT POD GALLING



MOLECULAR STRATEGIES FOR

ENGINEERING NEMATODE RESISTANCE

IN PLANTS

1. Strategies targeting directly the nematode

2. Strategies aimed at using or reinforcing existing plant

defense mechanisms

3. Strategies aimed at interfering in the nematode- plant

interaction



1.STRATEGIES TARGETING DIRECTLY

THE NEMATODE

Exploit the structural difference between nematodes and

plants

Eg:- chitin and collagen, both are important components

of the nematode and absent in plants

Transgenic plants expressing chitinase and collagenasewere constructed

Nematode resistant plants have not been reported so far



Cowpea Trypsin inhibitor [CpTI] isolated from Cowpea

(Vigna unguiculata) and the insecticidal crystal proteins

produced by B.thuringiensis isolates.

CpTI affected the sexual development of sedentary

endoparasitic cyst nematode Globodera palleda

Strategies aimed at targeting internal

nematode structures

Cont..



2. STRATEGIES AIMED AT USING OR

REINFORCING EXISTING PLANT

DEFENSE MECHANISMS

Isolating resistant genes and expressed in higher plants

Nematode resistant genes are present in several cropspecies

Important component of many breeding programsincluding those for tomato, soyabeans and cereals are

1. HsIPro-I

Against Heterodera schachtii.

2. Mi-I

Against Macrosiphum euphorbiae.

3. Gpa2

Against Globodera pallida.



LR TM

HsIPro-I

LZ NBS LRRMi-I

LZ NBS LRR Gpa2



3.STRATEGIES AIMED AT INTERFERING IN

THE NEMATODE- PLANT INTERACTION

Strategies aimed at blocking the nematode- plant

recognition- transgenic plant produce lectins

Strategies aimed at the inhibition or destruction of

specialised feeding structures

1. Destroy plant cells present in syncytium

2. Proteins synthesized by nematodes for the

maintenance of syncytium destroyed by plantibodies



RESISTANCE MECHANISMS

1. In resistant tomatoes a localized necrosis, suggesting a HR is

visible near the anterior end of the nematode within a few

days of infection.

2. HI (Gpa2) mediated resistance of potato, the feeding site

becomes surrounded by necrotic tissues and collapses.

3. HsIPro-I

Not involved in hypersensitive response. Nematode die in the

last J2 stage. Because of degradation of the feeding

structure(syncytium) in the host.



RESISTANT / NOT RESISTANT



CONCLUSION

Incorporation of natural resistance is a major strategy in

nematode management.

Not certain that genes function effectively in heterologous

hosts.

Investigation of cloned R genes allowed development of

designer R genes with faster response, broader target

recognition or increased durability.

Understanding the interactions between host and pathogen

increase options for control strategies.

Use of chemical nematicides decreases.



THANK YOU



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