Phytohormone Profiling of Wheat Seedlings in Responses to Hessian Fly Infestation

Lieceng Zhu1, Xiang Liu2, Ming-Shun Chen3

1Fayetteville State University2North Carolina State University3USDA-ARS in Manhattan, Kansas

Wheat - Hessian Fly Interaction

A gene for gene model

Incompatible Compatible

AvirulentVirulent

Control

• Physically damage plants

• Limited to a few cells

• Induces nutritive tissue formation at feeding sites (Harris et al. 2006)

Characteristics of Larval Feeding

• Sessile • Feed like pathogen

• Shift in carbon & nitrogen metabolism (Zhu et al. 2008)

• Differential genome-wide gene expression (Liu et al. 2007)

NC

CK

R

NC

S

NC

Question

How are responses of wheat seedlings to Hessian fly feeding regulated?

Phytohormone Profiling

GC-MS Analysis

Gas Chromatography

DetectorSeparator

Mass Spectrometry

• Determine concentration of several types of phytohormone simultaneously

Treatments

Genotype Sample 24 H 72 H

CK CK

Feeding sites R R

Molly S S

CK CK

Second leaf R R

S S

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

• No changes in second leaves

• Implication: Impacts of HF feeding on phytohormones is localized

Compatible Interaction

• IAA increased– Major form of Auxin

• Implication: IAA contributes to susceptibility

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

Gene Expression in JA Pathway

LOX 2

AOS

At VSP2

28S RNA

C R S C R S C R S

24H 48H 72H

18:3 FA

Membrane lipids

LOX2

AOS

AOC

OPDA

OPR3

JA

AtVSP2

(JA responsive)

• LOX2 & AOS: Compatible Incompatible • AtVSP2: Compatible Incompatible at 24 & 48H

• Implication:– OPDA was regulated at transcription level– AtVSP2 may be induced by OPDA– AtVSP2 is important in resistance

Summary

• Impact of HF larval feeding is localized• OPDA & SA may act together in wheat resistance to HF• IAA plays a role in susceptibility of wheat plants • Increases in OPDA in incompatible interaction is partially regulated

through gene transcription• AtVSP2 protein may be induced by OPDA & is critical to wheat

resistance to HF

Acknowledgement

• KSU Lipidomics Center– Dr. Richard Jeannotte, Ms. Alex Sparks

• Grant P20 MD001089 from the National Institutes of Health, NCMHD, the Department of Health & Human Services