Fighting Plants

Lieceng Zhu, PhDDepartment of Biological Sciences

Fayetteville State University

Plants Are Amazing!

Being Plants Are No Fun

Biotic Stress • Pathogens• Herbivores

Abiotic Stress

Run away?

No Fly, Fight or Die

Plant Defense

Ways & Means

• Cry for help• Talk and listen• Memory

• Chemical• Physicals

• Antibiosis• Antixenosis• Tolerance

• Local • Systemic

• Constitutive • Induced

Cry for Help

• The enemies of enemies are friends

Warn Friends & Neighbors/Talk & listen

Ian T. Baldwin, et al. 2006.Science (311) 812-815

Remember the Offense

Not forgotten, nor forgiven

Antixenosis(Deter or prevent)

• Physical: Trichome• Chemical: Smell/taste

AntibiosisAffect development & reproduce

• Toxic compounds• Less nutritive

ToleranceYou have your way, I have my way!

Chemical Defense

• Secondary metabolites– Alkaloids: Nicotine,

cocaine– Terpene (GLV)– Phenolics: Pyrethrin

Physical Defense

Constitutive & Induced Defense

Steps of Induced Defense Responses

• Perceive: Insect oral secretion

• Transduce signal: secondary messenger (Phytohormones)

• Defense response

Phytohormones & Fatty Acids

• Jasmonic acid (JA)• Salicylic acid (SA)• abscisic acid (ABA)• Auxin (IAA)• 12-Oxo-Phytodienoic Acid (OPDA)• Fatty acids

– Oleic acid (FA18:1)– Linolenic acid (FA18:3)

The Tale of Wheat & Hessian Fly

• Host & Parasite• Life & death

Wheat (Tricitcum aestivum)

• # 6• # 3 • # 3, 20% calories.

eggs on leaf

larvae pupae

adult

Hessian Fly (HF) (Mayetiola destructor)

• A family of Mosquito

• Asian-Europe-North American– Independent war

• Destructive

Wheat - Hessian fly Interaction

Host & parasite Life & death• larvae stage• Sessile• Inject toxin• Stunt & Kill

Resistant & Susceptible Plants in Fields

•

Resistant (A) and susceptible (B) wheat cultivars in Benton Co. MO, Dec. 2005. Photos: B. Schemerhorn, J. Stuart.

Wheat - Hessian Fly InteractionA gene for gene model

Incompatible Compatible

Avirulent Virulent

Control

vH13GP

Objective of Research

• Identify plant hormones related to resistance/susceptibility of of wheat to Hessian fly infestation

Significance

• Understand the molecular mechanism of plant resistance

• Develop cultivars with durable resistance

• Protect food & agriculture security

Materials & Methods

• Plant & insects• Infesting• Sampling• Phytohormone profiling

Plants

• Wheat Molly: At two leaf stage

Insects • Biotype GP (avirlulent) and vH13

(virulent)

Experiment Design

Genotype 24 H 72 H

CK CKMolly R (GP) R (GP)

S (vH13) S (vH13)

•5 reps

Infestation

Avirulent GP

Control (CK)

Incompatible (S)

Compatible (S)

Virulent vH13

How to infest?

•15 HF/pot

After Infestation

SamplingAvirulent

Control (CK)

Incompatible (S)

Compatible (S)

Virulent

Phytohormone Profiling

GC-MS Analysis

Gas Chromatography

DetectorSeparator

Mass Spectrometry

• Determine concentration of several types of phytohormone simultaneously

Results & Discussions

Phytohormone Profiling• 10 phytohormone/related compounds detected

IAA, SA, CA, BA, JA, OPDA, 18:3, 18:1, 18:2 & 18:0 FA

• IAA, SA, JA, OPDA, 18:1, 18:3 were affected at feeding sites

Avirulent

Control (CK) Incompatible (S) Compatible (S)

Virulent

Data file

• Excel file• Statistics: • Means – standard deviation– standard error– Chart

Compatible Interaction

• IAA increased– Major form of Auxin

• Implication: IAA contributes to susceptibility

0

50

100

150

200

250

300

350

400

450

500

24H 72H

Mea

n ±S

E (n

g/g

fres

h w

eigh

t)

IAA CRS

Incompatible Interaction• SA & OPDA increased

– Concentration (ng/ g fresh weight)

11 fold

8 fold

35 fold

18 fold

SA OPDA

18:3 FA

Membrane lipids

LOX2

AOS

AOC

OPDA

OPR3

JA

Response • 18:3 & 18:1 FA increased• JA decreased at 24 H• Implication:– JA may not regulate resistance– OPDA & SA may regulate resistant responses

Conclusion

• OPDA & SA may act together in wheat resistance to HF• IAA plays a role in susceptibility of wheat plants

• Zhu et al. JEE, (103) 178-185

The End