Use of silenced plants in allelopathy bioassays: a novel approach

Abstract

Volatile phytohormones or other chemicals can aVect processes in distal plant parts but may also inXuence neighboring plants, and thereby function allelopathically. While this hypothesis has been widely discussed, rigorous tests are lacking. Transgenic plants, silenced in the production of an emitted chemical, are ideal tools to test the hypothesis that the release of a chemical can negatively inXuence the growth of neighbors (allelopathy). We used isogenic wild type (WT) and genetically transformed plants that lacked the ability to produce ethylene (ir-aco), as both "emitters" and "receivers" of this volatile phytohormone in experiments where receiver plants were only exposed to the headspace of WT or ir-aco emitters, in order to evaluate if natural ethylene releases can function allelopathically. Root growth (a proxy of plant Wtness) of WT receivers correlated negatively with the number of WT emitters and headspace ethylene concentrations. Reducing ethylene concentrations in the headspace with the ethylene scrubber, KMnO 4 , and using ir-aco seedlings as emitters restored root growth of WT receiver seedlings. 1-Aminocyclopropane-1-carboxylic acid (ethylene biosynthesis substrate) supplementation to WT but not ir-aco emitters inhibited root growth of ir-aco, but not WT receivers, suggesting increased sensitivity to exogenous ethylene of ir-aco seedlings. We conclude that plants genetically silenced in the production of a putative allelochemical are useful in determining if the emitted chemical functions allelopathically.

Volatile chemicals from leaf litter are associated with invasiveness of a Neotropical weed in Asia

“…However, our results could be strengthened by comparisons of A. adenophora litter to litter from native plants in the invader's nonnative range in both pots and Petri dish experiments. Also, Inderjit et al (2009) suggested the use of ''silenced'' plants to acquire conclusive evidence that the release of chemicals does matter in plant-plant interactions, but silencing a perennial plant for the production of more than one chemical may be a significant challenge and performing field experiments with silenced plants is yet another challenge. Perhaps the best way to demonstrate the role of VOCs produced by A. adenophora VOCs in the field will be through manipulative field studies that discriminate the effects of VOCs from those of competitors, pathogens, and herbivores.…”

Volatile communication between plants that affects herbivory: a meta‐analysis

“…) and allelopathic to plant competitors (Karban ; Inderjit et al . ). These same volatiles attract the predators and parasites of herbivores that can decrease levels of damage inflicted by herbivory (Dicke & Sabelis ; Turlings et al .…”

“…For example, volatile emissions protect plants from heat and oxidative stresses (Loreto & Velikova 2001;Behnke et al 2007). The volatiles released by herbivory are often directly repellent to herbivores (Bernasconi et al 1998;De Moraes et al 2001) and allelopathic to plant competitors Inderjit et al 2009). These same volatiles attract the predators and parasites of herbivores that can decrease levels of damage inflicted by herbivory (Dicke & Sabelis 1988;Turlings et al 1990;Thaler 1999;Kessler & Baldwin 2001).…”

Root-emitted volatile organic compounds: can they mediate belowground plant-plant interactions?

“…In addition to these assays performed under laboratory conditions, field experiments (Karban et al 2000;Dolch and Tscharntke 2000;Heil and Silva Bueno 2007) and bioassays using transgenic plants unable to release ('mute emitters') or perceive ('deaf receivers') the key volatile signals Paschold et al 2006;Inderjit et al 2009) have demonstrated that VOCs can act as interplant signals in nature. Belowground, original experimental devices have been designed to study the roles played by root-emitted VOCs in biotic interactions.…”