Biology subjects

Erb, M.

Publications and source records attributed to Erb, M..

4 recordsLinked to original sources

bioRxiv2018

Root volatiles in plant-plant interactions I: Characterization of root sesquiterpene emissions from Centaurea stoebe and their effects on other plants

Volatile organic compounds (VOCs) emitted by plant leaves can influence the physiology of neighboring plants. In contrast to interactions above ground, little is known about the role of VOCs in belowground plant-plant interactions. Here, we characterize constitutive root volatile emissions of the spotted knapweed (Centaurea stoebe) and explore the impact of these volatiles on the germination and growth of different sympatric plant species. We show that C. stoebe roots emit high amounts of sesquiterpenes, with estimated release rates of (E)-{beta}-caryophyllene above 3 g g-1 dw h-1. Sesquiterpene emissions show little variation between different C. stoebe populations, but vary substantially between different Centaurea species. Through root transcriptome sequencing, we identify six root-expressed sesquiterpene synthases (TPSs). Two root-specific TPSs, CsTPS4 and CsTPS5, are sufficient to produce the full blend of emitted root sesquiterpenes. Volatile exposure experiments demonstrate that C. stoebe root volatiles have neutral to positive effects on the germination and growth of different sympatric neighbors. Thus, constitutive root sesquiterpenes produced by two C. stoebe TPSs are associated with facilitation of sympatric neighboring plants. The release of root VOCs may thus influence C. stoebe abundance and plant community structure in nature.

plant biology↗

bioRxiv2018

Root volatiles in plant-plant interactions II: Root terpenes from Centaurea stoebe modify Taraxacum officinale root chemistry and root herbivore growth

Volatile organic compounds (VOCs) emitted by plant roots can influence the germination and growth of neighboring plants. However, little is known about the effects of root VOCs on plant-herbivore interactions. The spotted knapeed (Centaurea stoebe) constitutively releases high amounts of sesquiterpenes into the rhizosphere. Here, we examine the impact of C. stoebe root VOCs on primary and secondary metabolites of sympatric Taraxacum officinale plants and the resulting plant-mediated effects on a generalist root herbivore, the white grub Melolontha melolontha. We show that exposure of T. officinale to C. stoebe root VOCs does not affect the accumulation of defensive secondary metabolites, but modulates carbohydrate and total protein levels in T. officinale roots. Furthermore, VOC exposure increases M. melolontha growth on T. officinale plants. Exposure of T. officinale to a major C. stoebe root VOC, the sesquiterpene (E)-{beta}-caryophyllene, partially mimics the effect of the full root VOC blend on M. melolontha growth. Thus, releasing root VOCs can modify plant-herbivore interactions of neighboring plants. The release of VOCs to increase the susceptibility of other plants may be a form of plant offense.

plant biology↗

bioRxiv2018

Molecular dissection of early defense signaling underlying volatile-mediated defense priming and herbivore resistance in rice

Herbivore-induced plant volatiles prime plant defenses and resistance. How volatiles are integrated into early defense signaling is not well understood. Furthermore, whether there is a causal relationship between volatile defense priming and herbivore resistance is unclear. Here, we investigated the impact of indole, a common herbivore-induced plant volatile and known defense priming cue, on early defense signaling and herbivore resistance in rice. We show that rice plants infested by Spodoptera frugiperda caterpillars release up to 25 ng*h-1. Exposure to equal doses of synthetic indole enhances rice resistance to S. frugiperda. Screening of early signaling components reveals that indole directly enhances the expression of the receptor like kinase OsLRR-RLK1. Furthermore, indole specifically primes the transcription, accumulation and activation of the mitogen-activated protein kinase OsMPK3 as well as the expression of the downstream WRKY transcription factor OsWRKY70 and several jasmonate biosynthesis genes, resulting in a higher accumulation of jasmonic acid (JA). Using transgenic plants defective in early signaling, we show that OsMPK3 is required, and that OsMPK6 and OsWRKY70 contribute to indole-mediated defense priming of JA-dependent herbivore resistance. We conclude that volatiles can increase herbivore resistance of plants by priming early defense signaling components.

plant biology↗

bioRxiv2018

Can herbivore-induced volatiles protect plants by increasing the herbivores’ susceptibility to natural pathogens?

In response to insect herbivory, plants mobilize various defenses. Defense responses include the release of herbivore-induced plant volatiles (HIPVs) that can serve as signals to alert undamaged tissues and to attract natural enemies of the herbivores. It has also been shown that some HIPVs can have a direct negative impact on herbivore survival, but it is not yet understood by what mechanism. Here we tested the hypothesis that exposure to HIPVs renders insects more susceptible to natural pathogens. Exposing caterpillars of the noctuid Spodoptera exigua to indole and linalool, but not exposure to (Z)-3-hexenyl acetate increased the susceptibility to its nucleopolyhedrovirus (SeMNPV). We also found that exposure to indole, but not exposure to linalool or (Z)-3-hexenyl acetate, increased the pathogenicity of Bacillus thuringiensis. Additional experiments revealed significant changes on gut microbiota composition after forty-eight hours of larval exposure to indole. Overall, these results provide evidences that certain HIPVs can strongly enhance the susceptibility of caterpillars to pathogens, possibly through effects on the insects gut microbiota. These findings suggest a novel mechanism by which HIPVs can protect plants from herbivorous insects.

microbiology↗