Chemical Communication Channels Research Articles

Unraveling the secrets of plant roots: Simplified method for large scale root exudate sampling and analysis in Arabidopsis thaliana

Background Plants exude a plethora of compounds to communicate with their environment. Although much is known about above-ground plant communication, we are only beginning to fathom the complexities of below-ground chemical communication channels. Studying root-exuded compounds and their role in plant communication has been difficult due to the lack of standardized methodologies. Here, we develop an interdisciplinary workflow to explore the natural variation in root exudate chemical composition of the model plant Arabidopsis thaliana. We highlight key challenges associated with sampling strategies and develop a framework for analyzing both narrow- and broad-scale patterns of root exudate composition in a large set of natural A. thaliana accessions. Methods Our method involves cultivating individual seedlings in vitro inside a plastic mesh, followed by a short hydroponic sampling period in small quantities of ultrapure water. The mesh makes it easy to handle plants of different sizes and allows for large-scale characterization of individual plant root exudates under axenic conditions. This setup can also be easily extended for prolonged temporal exudate collection experiments. Furthermore, the short sampling time minimizes the duration of the experiment while still providing sufficient signal even with small volume of the sampling solution. We used ultra-high performance liquid chromatography coupled with quadrupole time-of-flight mass spectrometry (UHPLC-QTOF-MS) for untargeted metabolic profiling, followed by tentative compound identification using MZmine3 and SIRIUS 5 software, to capture a broad overview of root exudate composition in A. thaliana accessions. Results Based on 28 replicates of the Columbia genotype (Col-0) compared with 10 random controls, MZmine3 annotated 354 metabolites to be present only in Col-0 by negative ionization. Of these, 254 compounds could be annotated by SIRIUS 5 software. Conclusions The methodology developed in this study can be used to broadly investigate the role of root exudates as chemical signals in plant belowground interactions.

Unraveling the secrets of plant roots: Simplified method for large scale root exudate sampling and analysis in Arabidopsis thaliana.

Background: Plants exude a plethora of compounds to communicate with their environment. Although much is known about above-ground plant communication, we are only beginning to fathom the complexities of below-ground chemical communication channels. Studying root-exuded compounds and their role in plant communication has been difficult due to the lack of standardized methodologies. Here, we develop an interdisciplinary workflow to explore the natural variation in root exudate chemical composition of the model plant Arabidopsis thaliana. We highlight key challenges associated with sampling strategies and develop a framework for analyzing both narrow- and broad-scale patterns of root exudate composition in a large set of natural A. thaliana accessions. Methods: Our method involves cultivating individual seedlings in vitro inside a plastic mesh, followed by a short hydroponic sampling period in small quantities of ultrapure water. The mesh makes it easy to handle plants of different sizes and allows for large-scale characterization of individual plant root exudates under axenic conditions. This setup can also be easily extended for prolonged temporal exudate collection experiments. Furthermore, the short sampling time minimizes the duration of the experiment while still providing sufficient signal even with small volume of the sampling solution. We used ultra-high performance liquid chromatography coupled with quadrupole time-of-flight mass spectrometry (UHPLC-QTOF-MS) for untargeted metabolic profiling, followed by tentative compound identification using MZmine3 and SIRIUS 5 software, to capture a broad overview of root exudate composition in A. thaliana accessions. Results: Based on 28 replicates of the Columbia genotype (Col-0) compared with 10 random controls, MZmine3 identified 354 metabolites to be present only in Col-0 by negative ionization. Of these, 254 compounds could be annotated by SIRIUS 5 software. Conclusions: The methodology developed in this study can be used to broadly investigate the role of root exudates as chemical signals in plant belowground interactions.

Unraveling the secrets of plant roots: Simplified method for large scale root exudate sampling and analysis in Arabidopsis thaliana

Background: Plants exude a plethora of compounds to communicate with their environment. Although much is known about above-ground plant communication, we are only beginning to fathom the complexities of below ground chemical communication channels. Studying root-exuded compounds and their role in plant communication has been difficult due to a lack of standardized methodologies. Here, we develop an interdisciplinary workflow to explore the natural variation in root exudate chemical composition of the model plant Arabidopsis thaliana. We highlight key challenges associated with sampling strategies and develop a framework for analyzing both narrow and broad scale patterns of root exudate composition in a large set of natural A. thaliana accessions. Methods: Our method involves cultivating individual seedlings in vitro inside a plastic mesh, followed by a short hydroponic sampling period in small quantities of ultrapure water. The mesh makes it easy to handle plants of different sizes and allows for large-scale characterization of individual plant root exudates in axenic conditions. This setup can also be easily extended for prolonged temporal exudate collection experiments. Furthermore, the short sampling time minimizes the duration of the experiment while still providing sufficient signal even with a small volume of sampling solution. We used ultra-high performance liquid chromatography coupled with quadrupole time-of-flight mass spectrometry (UHPLC-QTOF-MS) for untargeted metabolic profiling, followed by tentative compound identification using MZMine3 and SIRIUS 5 software, to capture a broad overview of root exudate composition in A. thaliana accessions. Results: Based on 28 replicates of Columbia genotype (Col-0) compared with 10 random biological controls, MZMine3 identified 354 metabolites to be present only in Col-0 by negative ionization. Of these, 313 compounds could be annotated by SIRIUS 5 software. Conclusions: The methodology developed in this study can be used to broadly investigate the role of root exudates as chemical signals in plant belowground interactions.

Light alters activity but does not disturb tandem coordination of termite mating pairs

AbstractGroup‐living animals coordinate their movements via local interactions, which can be mediated by visual, tactile, and chemical communication channels. Termite mating pairs form tandems with one male imago following one female imago in a synchronised way to explore the environment and search for a nesting site. Imagoes are the only developmental stage with compound eyes in termites, but the role of vision during tandem runs remains unknown. Here, we investigate the movements during tandem runs of two termite species, Coptotermes formosanus, which swarms during the night, and Reticulitermes speratus, which swarms during the day. We performed the experiments with light and in complete darkness. We found that females and males of both species adjust their speed to each other to form a stable tandem and reunite efficiently upon separation, with or without light. However, the activity was dependent on light conditions in the diurnal R. speratus, in which termites were more active with light. On the other hand, the nocturnal C. formosanus was mostly insensitive to light environments, with termites being slightly more active in darkness. Our results suggest that termites can use light as an environmental cue to start forming mating pairs but not as means to locate mates or coordinate their movements.

Enzyme-mediated nitric oxide production in vasoactive erythrocyte membrane-enclosed coacervate protocells.

The design and construction of synthetic therapeutic protocells capable of establishing cognate chemical communication channels with living cells is an important challenge for synthetic biology and bio-engineering. Here we develop a step towards protocell-mediated nitric-oxide-induced vasodilation by constructing a new synthetic cell model based on bio-derived coacervate vesicles with high haemocompatibility and increased blood circulation times. The hybrid protocells are prepared by the spontaneous self-assembly of haemoglobin-containing erythrocyte membrane fragments on the surface of preformed polysaccharide-polynucleotide coacervate micro-droplets containing glucose oxidase. We use the sequestered enzymes to program a spatially coupled glucose oxidase/haemoglobin reaction cascade, which in the presence of glucose and hydroxyurea generates a protocell-mediated flux of nitric oxide that we exploit for in vitro and in vivo blood vessel vasodilation. Taken together, our results provide new opportunities for the development of endogenously organized cell-like entities (biocompatible micro-bots) geared specifically towards active interfacing with individual living cells and cell communities.

Cuticular hydrocarbon divergence in the jewel wasp Nasonia: evolutionary shifts in chemical communication channels?

The evolution and maintenance of intraspecific communication channels constitute a key feature of chemical signalling and sexual communication. However, how divergent chemical communication channels evolve while maintaining their integrity for both sender and receiver is poorly understood. In this study, we compare male and female cuticular hydrocarbon (CHC) profiles in the jewel wasp genus Nasonia, analyse their chemical divergence and investigate their role as species-specific sexual signalling cues. Males and females of all four Nasonia species showed unique, nonoverlapping CHC profiles unambiguously separating them. Surprisingly, male and female phylogenies based on the chemical distances between their CHC profiles differed dramatically, where only male CHC divergence parallels the molecular phylogeny of Nasonia. In particular, N.giraulti female CHC profiles were the most divergent from all other species and very different from its most closely related sibling species N.oneida. Furthermore, although our behavioural assays indicate that female CHC profiles can generally be perceived as sexual cues attracting males in Nasonia, this function has apparently been lost in the highly divergent female N.giraulti CHC profiles. Curiously, N.giraulti males are still attracted to heterospecific, but not to conspecific female CHC profiles. We suggest that this striking discrepancy has been caused by an extensive evolutionary shift in female N.giraulti CHC profiles, which are no longer used as conspecific recognition cues. Our study constitutes the first report of an apparent abandonment of a sexual recognition cue that the receiver did not adapt to.

Heavy metal stress can prime for herbivore‐induced plant volatile emission

Heavy metals are important pollutants that can severely impact ecological foodwebs. In addition to direct toxic effects, these contaminants have been suggested to disrupt chemical communication channels between plants and insects that rely on volatile organic compounds (VOCs). We investigated how different concentrations of copper (Cu) and cadmium (Cd) stress affect the capacity of Zea mays to synthesize VOCs in the presence and absence of herbivorous insects. Hydroponically grown maize exposed to a high and low concentration of either Cu or Cd showed stunted growth and lower photosynthetic capacities. Herbivores feeding on stressed plants also had attenuated growth rates. Heavy metal treatment alone did not induce VOC emission in maize plants; however, the higher Cu dose was found to prime for enhanced volatile production that can be triggered by caterpillar feeding. Cu stress correlated with increased levels of reactive oxygen species in roots and priming of herbivore-induced jasmonic acid in leaves. Plants challenged with Cd and herbivory did not differ in responses compared with herbivore-damaged controls with no heavy metals added to the substrate. For Cu stress, our results support the 'single biochemical mechanism for multiple stressors' model which predicts overlapping signalling and responses to abiotic and biotic stress factors.

A synomone imparting distinct sex pheromone communication channels for Choristoneura rosaceana (Harris) and Pandemis limitata (Robinson) (Lepidoptera: Tortricidae)

Male obliquebanded leafrollers, Choristoneura rosaceana (Harris), were induced to respond to a pheromone source tainted with a behavioural antagonist, Z9-tetradecenyl acetate, when a source releasing the antagonist was placed 10 cm upwind of the tainted source in a wind tunnel. However, placement of the antagonist upwind of an attractive pheromone source did not interrupt pheromone-mediated responses. Placement of a source releasing Z9-tetradecenyl acetate, a minor pheromone component of the sympatric species, the threelined leafroller, Pandemis limitata (Robinson), upwind of a calling P. limitata female, reduced conspecific male pheromone-mediated response but resulted in upwind flight by male C. rosaceana and contact with heterospecific females. Male P. limitata locked on and flew upwind to but did not contact heterospecific females when a source releasing Z9-tetradecenyl acetate was positioned upwind of a calling C. rosaceana female. In the field, adaptation or habituation to Z9-tetradecenyl acetate caused by atmospheric treatment with this compound apparently resulted in reciprocal heterospecific pheromone responses. More C. rosaceana males were captured in traps baited with their pheromone and the behavioural antagonist in small field plots treated atmospherically with Z9-tetradecenyl acetate than in nontreated control plots. Fewer male P. limitata were captured in traps baited with their own pheromone, or with C. rosaceana pheromone tainted with Z9-tetradecenyl acetate in plots treated atmospherically with Z9-tetradecenyl acetate than in nontreated control plots. We argue that Z9-tetradecenyl acetate is an important synomone which assists in partitioning the sexual chemical communication channels of C. rosaceana and P. limitata.

Perireceptor Events in Pheromone Perception in Scarab Beetles

Despite the remarkable diversity of the sex pheromone chemistry in scarab beetles, various species utilize a common type of γ-lactones in their chemical communication channels. These compounds differ primarily in length of the alkenyl side chain and the stereochemistry at the chiral center. Two species, Anomala osakana and Popillia japonica, utilize the opposite enantiomers of japonilure as sex pheromones. Each species produces only one of the enantiomers that functions as its own sex pheromone and as a behavioral antagonist to the alloreceiver. Pheromone binding proteins (PBPs) have been characterized, which are present in these and several other scarab species. In most cases there was only one class of PBP, which was expressed in both sexes. A. osakana and P. japonica possess each one single PBP with high homology to each other. In each species the same PBP seems to recognize both enantiomers of japonilure, i. e., the pheromonal and the “stop” signals. Based on the N-terminal sequences, the antennae-specific proteins from various other species were highly conserved within the family and showed moderate homology to putative odorant binding protein from Drosophila melanogaster (47%), Lygus lineolaris (45∼50%) and the ABPX protein from Bombyx mori (30∼35%). From analysis of extracts of soluble antennal proteins from several species, significant degradation of the γ-lactones (buibuilactone, japonilure) was detected, essentially in all of them, even in species that do not use these compounds as pheromones. Recently a peculiar pheromone with a diamide moiety [1, 3-dimethyl-2, 4-(1 H, 3 H)-quinazolinedione] was isolated from Phyllopertha diversa, which was rapidly degraded by antennal enzymes from this species. Beetles that utilize lactones as their pheromones possess little or no ability to metabolize this compound.

Synthesis and field screening of chiral monounsaturated epoxides as lepidopteran sex attractants and sex pheromone components

Enantiomerically enriched forms of (Z)-6-cis-9,10-epoxymonoenes and (Z)-9-cis-6,7-epoxymonoenes of chain lengths C17-20 were synthesized by Sharpless asymmetric epoxidation of allylic alcohol intermediates, followed by tosylation or halogenation and chain extension. The resulting monounsaturated epoxides were field tested as sex attractants for lepidopteran species.Euchlaena madusaria Walker males were attracted to blends of the enantiomers of (Z)-6- cis- 9,10-epoxynonadecene 6Z-cis-9,10-epoxy-19:H; IUPAC name [2α,3α(Z)]-2-pentyl-3-(2-dodecenyI)oxirane in combination with 6Z,9Z-19: H. The response was antagonized by 9Z-cis-6,7-epoxy-19: H. 6Z,9Z-19: H was tentatively identified in pheromone gland extracts.Xanthotype sospeta Drury male moths were attracted to lures containing 6Z-9S,10R-epoxy-19: H; the response was antagonized by the opposite enantiomer.Pal-this angulalis Hübner males were attracted to 9Z-6S,7R-epoxy-19:H; the opposite enantiomer was antagonistic. 6Z,9Z-19:H and 9Z-cis-6,7-epoxy-19:H and 9Z-cis-6,7-epoxy-19:H were tentatively identified in pheromone gland extracts fromAnacamptodes humaria Guenée females. In field trails, 9Z-6R,7S-epoxy-19:H proved to be the attractive enantiomer, and the response was potentiated by 6Z,9Z-19:H. Mechanisms by which unique chemical communication channels are maintained by each species are discussed.

Chiral Lepidopteran Sex Attractants: Blends of Optically Active C 20 and C 21 Diene Epoxides as Sex Attractants for Geometrid and Noctuid Moths (Lepidoptera)

Sex attractants and behavioral antagonists comprising C20 and C21 triene hydrocarbons and chiral epoxydienes are reported for male moths of two noctuid and six geometrid species. Moths of the noctuid Idia americalis (Guenee) were attracted to lures containing a 1:1 mixture of 3 Z ,9 Z -6 S ,7 R -epoxy-eicosadiene (3 Z ,9 Z -6 S ,7 R -epoxy-20:H) and 3 Z ,9 Z -6 S ,7 R -epoxy-21:H. Moths of the noctuid species Bleptina caradrinalis (Guenee) were specifically attracted to a blend consisting of a 1:1 mixture of the enantiomers of 3 Z ,9 Z - cis -6,7-epoxy-20:H and to a 4:1 mixture of the enantiomers of 3 Z ,9 Z - cis -6,7-epoxy-21:H. The following geometrid moth species were also caught (optimum lure components in parentheses): Plagodis alcoolaria (Guenee) (3 Z ,9 Z -6 R ,7 S -epoxy-20:H + 3 Z ,6 Z ,9 Z -20:H), Xanthorhoe munitata Hubner (3 Z ,9 Z -6 S ,7 R -epoxy-21:H + 3 Z ,6 Z ,9 Z -21:H), X. abrasaria aquilonaria (Herrich-Schaffer) (3 Z ,9 Z -6 S ,7 R -epoxy-21:H + 3 Z ,6 Z -9 S ,10 R -epoxy-21:H), X. ferrugata (Clerck) (3 Z ,9 Z -6 S ,7 R -epoxy-21:H), Mesoleuca ruficillata (Guenee) (3 Z ,6 Z ,9 Z -20:H or 3 Z ,6 Z ,9 Z -21:H or both), and Anticlea vasiliata (Guenee) (3 Z ,6 Z ,9 Z -21:H). Chiral and achiral attractants for one species often acted as antagonists for closely related or sympatrie species, indicating how discrete chemical communication channels may be maintained.