Within-plant signaling by volatiles leads to induction and priming of an indirect plant defense in nature

Terrestrial plants serve as large and diverse habitats for a wide range of pathogenic and nonpathogenic microbes, yet these communities are not well described and little is known about the effects of plant defense on microbial communities in nature. We designed a field experiment to determine how variation in two plant defense signaling pathways affects the size, diversity, and composition of the natural endophytic and epiphytic bacterial communities of Arabidopsis thaliana. To do this, we provide an initial characterization of these bacterial communities in one population in southwestern Michigan, United States, and we compare these two communities among A. thaliana mutants deficient in salicylic acid (SA) and jasmonic acid (JA) signaling defense pathways, controls, and plants with artificially elevated levels of defense. We identified 30 distinct bacterial groups on A. thaliana that differ in colony morphology and 16S rRNA sequence. We show that induction of SA-mediated defenses reduced endophytic bacterial community diversity, whereas plants deficient in JA-mediated defenses experienced greater epiphytic bacterial diversity. Furthermore, there was a positive relationship between total community size and diversity, indicating that relatively susceptible plants should, in general, harbor higher bacterial diversity. This experiment provides novel information about the ecology of bacteria on A. thaliana and demonstrates that variation in two specific plant-signaling defense pathways can influence bacterial diversity on plants.

Download Full-text

Elucidating the Formation of Geranyllinalool, the Precursor of the Volatile C16-Homoterpene TMTT Involved in Indirect Plant Defense

Isoprenoid Synthesis in Plants and Microorganisms ◽

10.1007/978-1-4614-4063-5_13 ◽

2012 ◽

pp. 185-198

Author(s):

Marco Herde ◽

Katrin Gärtner ◽

Tobias Köllner ◽

Benjamin Fode ◽

Wilhelm Boland ◽

...

Keyword(s):

Plant Defense ◽

Indirect Plant Defense

Download Full-text

Variation in natural plant products and the attraction of bodyguards involved in indirect plant defenseThe present review is one in the special series of reviews on animal–plant interactions.

Canadian Journal of Zoology ◽

10.1139/z10-032 ◽

2010 ◽

Vol 88 (7) ◽

pp. 628-667 ◽

Cited By ~ 196

Author(s):

Roland Mumm ◽

Marcel Dicke

Keyword(s):

Plant Defense ◽

Natural Enemies ◽

Abiotic Factors ◽

Green Leaf Volatiles ◽

Research Field ◽

Trophic Levels ◽

Plant Interactions ◽

Leaf Volatiles ◽

Plant Volatile ◽

Indirect Plant Defense

Plants can respond to feeding or egg deposition by herbivorous arthropods by changing the volatile blend that they emit. These herbivore-induced plant volatiles (HIPVs) can attract carnivorous natural enemies of the herbivores, such as parasitoids and predators, a phenomenon that is called indirect plant defense. The volatile blends of infested plants can be very complex, sometimes consisting of hundreds of compounds. Most HIPVs can be classified as terpenoids (e.g., (E)-β-ocimene, (E,E)-α-farnesene, (E)-4,8-dimethyl-1,3,7-nonatriene), green leaf volatiles (e.g., hexanal, (Z)-3-hexen-1-ol, (Z)-3-hexenyl acetate), phenylpropanoids (e.g., methyl salicylate, indole), and sulphur- or nitrogen-containing compounds (e.g., isothiocyanates or nitriles, respectively). One highly intriguing question has been which volatiles out of the complex blend are the most important ones for the carnivorous natural enemies to locate "suitable host plants. Here, we review the methods and techniques that have been used to elucidate the carnivore-attracting compounds. Electrophysiological methods such as electroantennography have been used with parasitoids to elucidate which compounds can be perceived by the antennae. Different types of elicitors and inhibitors have widely been applied to manipulate plant volatile blends. Furthermore, transgenic plants that were genetically modified in specific steps in one of the signal transduction pathways or biosynthetic routes have been used to find steps in HIPV emission crucial for indirect plant defense. Furthermore, we provide an overview on biotic and abiotic factors that influence the emission of HIPVs and how this can affect the interactions between members of different trophic levels. Consequently, we review the progress that has been made in this exciting research field during the past 30 years since the first studies on HIPVs emerged and we highlight important issues to be addressed in the future.

Download Full-text