Caterpillar herbivory and salivary enzymes decrease transcript levels of Medicago truncatula genes encoding early enzymes in terpenoid biosynthesis

Jacqueline C. Bede, Richard O. Musser, Gary W. Felton, Kenneth L. Korth

Research output: Contribution to journalArticle

109 Citations (Scopus)

Abstract

In response to caterpillar herbivory, alfalfa and related plant species defend themselves through the induction of saponin and volatile terpenoid biosynthesis. Both these types of defensive compounds are derived from the metabolic intermediate, isopentenyl diphosphate (IPP). In plants, two distinct biosynthetic pathways can generate IPP; the cytosolic mevalonate pathway and the plastid-associated 2C-methyl erythritol 4-phosphate (MEP) pathway. In Medicago truncatula, transcript levels of key regulatory genes active in the early steps of these biosynthetic pathways were measured in response to larval herbivory by the beet armyworm, Spodoptera exigua. Transcripts encoding enzymes at early steps of both terpenoid pathways were lower in caterpillar-damaged leaves. Higher degrees of herbivore damage accentuated the decrease in transcript levels; however, transcript amounts were not affected by insect larval stage. Insect larvae, manipulated to reduce labial gland salivary secretions, were used to examine the role of the salivary elicitors in modulating gene expression. Results suggest that an insect salivary factor, possibly glucose oxidase (GOX), may be involved in reduction of transcript levels following herbivory. Addition of GOX or hydrogen peroxide to mechanically wounded leaves confirm these findings. In comparison, transcript levels of a gene encoding a putative terpene synthase are induced in mechanically- or insect-damaged leaves. These data show that insect salivary factors can act to suppress transcript levels of genes involved in plant defense pathways. Findings also suggest that in response to stress such as insect herbivory, regulation occurs at the early steps of the MEP pathway.

Original languageEnglish (US)
Pages (from-to)519-531
Number of pages13
JournalPlant molecular biology
Volume60
Issue number4
DOIs
StatePublished - Mar 1 2006

Fingerprint

Medicago truncatula
Herbivory
Terpenes
terpenoids
Insects
insect larvae
herbivores
biosynthesis
insects
erythritol
Enzymes
enzymes
glucose oxidase
Spodoptera exigua
Genes
Glucose Oxidase
genes
Biosynthetic Pathways
biochemical pathways
phosphates

All Science Journal Classification (ASJC) codes

  • Agronomy and Crop Science
  • Genetics
  • Plant Science

Cite this

@article{22578dc515a141019cd6afc6bea6169b,
title = "Caterpillar herbivory and salivary enzymes decrease transcript levels of Medicago truncatula genes encoding early enzymes in terpenoid biosynthesis",
abstract = "In response to caterpillar herbivory, alfalfa and related plant species defend themselves through the induction of saponin and volatile terpenoid biosynthesis. Both these types of defensive compounds are derived from the metabolic intermediate, isopentenyl diphosphate (IPP). In plants, two distinct biosynthetic pathways can generate IPP; the cytosolic mevalonate pathway and the plastid-associated 2C-methyl erythritol 4-phosphate (MEP) pathway. In Medicago truncatula, transcript levels of key regulatory genes active in the early steps of these biosynthetic pathways were measured in response to larval herbivory by the beet armyworm, Spodoptera exigua. Transcripts encoding enzymes at early steps of both terpenoid pathways were lower in caterpillar-damaged leaves. Higher degrees of herbivore damage accentuated the decrease in transcript levels; however, transcript amounts were not affected by insect larval stage. Insect larvae, manipulated to reduce labial gland salivary secretions, were used to examine the role of the salivary elicitors in modulating gene expression. Results suggest that an insect salivary factor, possibly glucose oxidase (GOX), may be involved in reduction of transcript levels following herbivory. Addition of GOX or hydrogen peroxide to mechanically wounded leaves confirm these findings. In comparison, transcript levels of a gene encoding a putative terpene synthase are induced in mechanically- or insect-damaged leaves. These data show that insect salivary factors can act to suppress transcript levels of genes involved in plant defense pathways. Findings also suggest that in response to stress such as insect herbivory, regulation occurs at the early steps of the MEP pathway.",
author = "Bede, {Jacqueline C.} and Musser, {Richard O.} and Felton, {Gary W.} and Korth, {Kenneth L.}",
year = "2006",
month = "3",
day = "1",
doi = "10.1007/s11103-005-4923-y",
language = "English (US)",
volume = "60",
pages = "519--531",
journal = "Plant Molecular Biology",
issn = "0167-4412",
publisher = "Springer Netherlands",
number = "4",

}

Caterpillar herbivory and salivary enzymes decrease transcript levels of Medicago truncatula genes encoding early enzymes in terpenoid biosynthesis. / Bede, Jacqueline C.; Musser, Richard O.; Felton, Gary W.; Korth, Kenneth L.

In: Plant molecular biology, Vol. 60, No. 4, 01.03.2006, p. 519-531.

Research output: Contribution to journalArticle

TY - JOUR

T1 - Caterpillar herbivory and salivary enzymes decrease transcript levels of Medicago truncatula genes encoding early enzymes in terpenoid biosynthesis

AU - Bede, Jacqueline C.

AU - Musser, Richard O.

AU - Felton, Gary W.

AU - Korth, Kenneth L.

PY - 2006/3/1

Y1 - 2006/3/1

N2 - In response to caterpillar herbivory, alfalfa and related plant species defend themselves through the induction of saponin and volatile terpenoid biosynthesis. Both these types of defensive compounds are derived from the metabolic intermediate, isopentenyl diphosphate (IPP). In plants, two distinct biosynthetic pathways can generate IPP; the cytosolic mevalonate pathway and the plastid-associated 2C-methyl erythritol 4-phosphate (MEP) pathway. In Medicago truncatula, transcript levels of key regulatory genes active in the early steps of these biosynthetic pathways were measured in response to larval herbivory by the beet armyworm, Spodoptera exigua. Transcripts encoding enzymes at early steps of both terpenoid pathways were lower in caterpillar-damaged leaves. Higher degrees of herbivore damage accentuated the decrease in transcript levels; however, transcript amounts were not affected by insect larval stage. Insect larvae, manipulated to reduce labial gland salivary secretions, were used to examine the role of the salivary elicitors in modulating gene expression. Results suggest that an insect salivary factor, possibly glucose oxidase (GOX), may be involved in reduction of transcript levels following herbivory. Addition of GOX or hydrogen peroxide to mechanically wounded leaves confirm these findings. In comparison, transcript levels of a gene encoding a putative terpene synthase are induced in mechanically- or insect-damaged leaves. These data show that insect salivary factors can act to suppress transcript levels of genes involved in plant defense pathways. Findings also suggest that in response to stress such as insect herbivory, regulation occurs at the early steps of the MEP pathway.

AB - In response to caterpillar herbivory, alfalfa and related plant species defend themselves through the induction of saponin and volatile terpenoid biosynthesis. Both these types of defensive compounds are derived from the metabolic intermediate, isopentenyl diphosphate (IPP). In plants, two distinct biosynthetic pathways can generate IPP; the cytosolic mevalonate pathway and the plastid-associated 2C-methyl erythritol 4-phosphate (MEP) pathway. In Medicago truncatula, transcript levels of key regulatory genes active in the early steps of these biosynthetic pathways were measured in response to larval herbivory by the beet armyworm, Spodoptera exigua. Transcripts encoding enzymes at early steps of both terpenoid pathways were lower in caterpillar-damaged leaves. Higher degrees of herbivore damage accentuated the decrease in transcript levels; however, transcript amounts were not affected by insect larval stage. Insect larvae, manipulated to reduce labial gland salivary secretions, were used to examine the role of the salivary elicitors in modulating gene expression. Results suggest that an insect salivary factor, possibly glucose oxidase (GOX), may be involved in reduction of transcript levels following herbivory. Addition of GOX or hydrogen peroxide to mechanically wounded leaves confirm these findings. In comparison, transcript levels of a gene encoding a putative terpene synthase are induced in mechanically- or insect-damaged leaves. These data show that insect salivary factors can act to suppress transcript levels of genes involved in plant defense pathways. Findings also suggest that in response to stress such as insect herbivory, regulation occurs at the early steps of the MEP pathway.

UR - http://www.scopus.com/inward/record.url?scp=33644841888&partnerID=8YFLogxK

UR - http://www.scopus.com/inward/citedby.url?scp=33644841888&partnerID=8YFLogxK

U2 - 10.1007/s11103-005-4923-y

DO - 10.1007/s11103-005-4923-y

M3 - Article

C2 - 16525889

AN - SCOPUS:33644841888

VL - 60

SP - 519

EP - 531

JO - Plant Molecular Biology

JF - Plant Molecular Biology

SN - 0167-4412

IS - 4

ER -