TY - JOUR
T1 - Herbivore-induced volatiles in the perennial shrub, Vaccinium corymbosum, and their role in inter-branch signaling
AU - Rodriguez-Saona, Cesar R.
AU - Rodriguez-Saona, Luis E.
AU - Frost, Christopher J.
N1 - Funding Information:
Acknowledgments We are grateful to Drs. Paul Paré and Nicholi Vorsa for their comments on the manuscript. We thank Robert Holdcraft for his help with the tables and figures, Vera Kyryczenko-Roth for technical assistance, Dr. Philip Taylor (USDA-ARS, Beneficial Insects Introduction Research Unit, Newark, DE) for the supply of gypsy moth egg masses and caterpillars, and Dr. Thomas Hartman (Rutgers University, Mass Spectrometry Support Facility, New Brunswick, NJ) for identification of volatiles. Funding for this study was provided by USDA-CREES Special Grant (Project No. 2006-34155-17118) and hatch funds (Project No. NJ08192) to C.R.-S., and by the USDA-NRI (Project No. 2007-35302-18087) to C.J.F.
PY - 2009/2
Y1 - 2009/2
N2 - Herbivore feeding activates plant defenses at the site of damage as well as systemically. Systemic defenses can be induced internally by signals transported via phloem or xylem, or externally transmitted by volatiles emitted from the damaged tissues. We investigated the role of herbivore-induced plant volatiles (HIPVs) in activating a defense response between branches in blueberry plants. Blueberries are perennial shrubs that grow by initiating adventitious shoots from a basal crown, which produce new lateral branches. This type of growth constrains vascular connections between shoots and branches within plants. While we found that leaves within a branch were highly connected, vascular connectivity was limited between branches within shoots and absent between branches from different shoots. Larval feeding by gypsy moth, exogenous methyl jasmonate, and mechanical damage differentially induced volatile emissions in blueberry plants, and there was a positive correlation between amount of insect damage and volatile emission rates. Herbivore damage did not affect systemic defense induction when we isolated systemic branches from external exposure to HIPVs. Thus, internal signals were not capable of triggering systemic defenses among branches. However, exposure of branches to HIPVs from an adjacent branch decreased larval consumption by 70% compared to those exposed to volatiles from undamaged branches. This reduction in leaf consumption did not result in decreased volatile emissions, indicating that leaves became more responsive to herbivory (or "primed") after being exposed to HIPVs. Chemical profiles of leaves damaged by gypsy moth caterpillars, exposed to HIPVs, or non-damaged controls revealed that HIPV-exposed leaves had greater chemical similarities to damaged leaves than to control leaves. Insect-damaged leaves and young HIPV-exposed leaves had higher amounts of endogenous cis-jasmonic acid compared to undamaged and non-exposed leaves, respectively. Our results show that exposure to HIPVs triggered systemic induction of direct defenses against gypsy moth and primed volatile emissions, which can be an indirect defense. Blueberry plants appear to rely on HIPVs as external signals for inter-branch communication.
AB - Herbivore feeding activates plant defenses at the site of damage as well as systemically. Systemic defenses can be induced internally by signals transported via phloem or xylem, or externally transmitted by volatiles emitted from the damaged tissues. We investigated the role of herbivore-induced plant volatiles (HIPVs) in activating a defense response between branches in blueberry plants. Blueberries are perennial shrubs that grow by initiating adventitious shoots from a basal crown, which produce new lateral branches. This type of growth constrains vascular connections between shoots and branches within plants. While we found that leaves within a branch were highly connected, vascular connectivity was limited between branches within shoots and absent between branches from different shoots. Larval feeding by gypsy moth, exogenous methyl jasmonate, and mechanical damage differentially induced volatile emissions in blueberry plants, and there was a positive correlation between amount of insect damage and volatile emission rates. Herbivore damage did not affect systemic defense induction when we isolated systemic branches from external exposure to HIPVs. Thus, internal signals were not capable of triggering systemic defenses among branches. However, exposure of branches to HIPVs from an adjacent branch decreased larval consumption by 70% compared to those exposed to volatiles from undamaged branches. This reduction in leaf consumption did not result in decreased volatile emissions, indicating that leaves became more responsive to herbivory (or "primed") after being exposed to HIPVs. Chemical profiles of leaves damaged by gypsy moth caterpillars, exposed to HIPVs, or non-damaged controls revealed that HIPV-exposed leaves had greater chemical similarities to damaged leaves than to control leaves. Insect-damaged leaves and young HIPV-exposed leaves had higher amounts of endogenous cis-jasmonic acid compared to undamaged and non-exposed leaves, respectively. Our results show that exposure to HIPVs triggered systemic induction of direct defenses against gypsy moth and primed volatile emissions, which can be an indirect defense. Blueberry plants appear to rely on HIPVs as external signals for inter-branch communication.
KW - External signaling
KW - Herbivore-induced plant volatiles
KW - Lymantria dispar
KW - Priming
KW - Vaccinium corymbosum
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UR - http://www.scopus.com/inward/citedby.url?scp=67349098747&partnerID=8YFLogxK
U2 - 10.1007/s10886-008-9579-z
DO - 10.1007/s10886-008-9579-z
M3 - Article
C2 - 19159981
AN - SCOPUS:67349098747
SN - 0098-0331
VL - 35
SP - 163
EP - 175
JO - Journal of Chemical Ecology
JF - Journal of Chemical Ecology
IS - 2
ER -