Abstract
Herbivore-induced volatile organic compounds prime non-attacked plant tissues to respond more strongly to subsequent attacks. However, the key volatiles that trigger this primed state remain largely unidentified. In maize, the release of the aromatic compound indole is herbivore-specific and occurs earlier than other induced responses. We therefore hypothesized that indole may be involved in airborne priming. Using indole-deficient mutants and synthetic indole dispensers, we show that herbivore-induced indole enhances the induction of defensive volatiles in neighbouring maize plants in a species-specific manner. Furthermore, the release of indole is essential for priming of mono- and homoterpenes in systemic leaves of attacked plants. Indole exposure markedly increases the herbivore-induced production of the stress hormones jasmonate-isoleucine conjugate and abscisic acid, which represents a likely mechanism for indole-dependent priming. These results demonstrate that indole functions as a rapid and potent aerial priming agent that prepares systemic tissues and neighbouring plants for incoming attacks.
Highlights
Herbivore-induced volatile organic compounds prime non-attacked plant tissues to respond more strongly to subsequent attacks
As altering the capacity of plants to produce Herbivoreinduced plant volatiles (HIPVs) may lead to unwanted pleiotropic effects, we propose a combination of plant manipulation and synthetic HIPV supplementation as a way forward to compensate for some of the major limitations of each individual approach
By exposing maize plants to herbivore-induced volatiles of igl mutants or wild-type Igl allele (WT) plants and to synthetic indole released from dispensers at physiologically relevant concentrations, we show that volatile indole serves as an essential within-plant and plant– plant priming signal in maize
Summary
Herbivore-induced volatile organic compounds prime non-attacked plant tissues to respond more strongly to subsequent attacks. Indole exposure markedly increases the herbivore-induced production of the stress hormones jasmonate-isoleucine conjugate and abscisic acid, which represents a likely mechanism for indole-dependent priming These results demonstrate that indole functions as a rapid and potent aerial priming agent that prepares systemic tissues and neighbouring plants for incoming attacks. The use of ‘deaf’ and ‘mute’ plants has been advocated as a complementary approach to study volatile plant–plant communication[6] Using this method, it was found that neither GLVs nor terpenoids prime the expression of defence genes in Nicotiana attenuata[34]. By exposing maize plants to herbivore-induced volatiles of igl mutants or WT plants and to synthetic indole released from dispensers at physiologically relevant concentrations, we show that volatile indole serves as an essential within-plant and plant– plant priming signal in maize
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