Plasmid engineering of aphid alarm pheromone in tobacco seedlings affects the preference of aphids

The Ecological Significance of Aphid Cornicles and Their Secretions

Aphid cornicles are abdominal appendages that secrete an array of volatile and nonvolatile compounds with diverse ecological functions. The emission of alarm pheromones yields altruistic benefits for clone-mates in the aphid colony, which is essentially a superorganism with a collective fate. Secreted droplets also contain unsaturated triglycerides, fast-drying adhesives that can be lethal when smeared on natural enemies but more often impede their foraging efficiency. The longest cornicles have evolved in aphids that feed in exposed locations and are likely used to scent-mark colony intruders. Reduced cornicles are associated with reliance on alternative defenses, such as the secretion of protective waxes or myrmecophily. Root-feeding and gall-forming lifestyles provide protected feeding sites and are associated with an absence of cornicles. In some eusocial gall-formers, soldier morphs become repositories of cornicle secretion used to defend the gall, either as menopausal apterae that defend dispersing alatae or as sterile first instars that dispatch predators with their stylets and use cornicle secretions as a construction material for gall repair. Collectively, the evidence is consistent with an adaptive radiation of derived cornicle functions molded by the ecological lifestyle of the aphid lineage.

Transcriptomic and metabolomic changes triggered by Macrosiphum rosivorum in rose (Rosa longicuspis)

BACKGROUND

Rose is one of the most popular flowers in the wold. Its field growth and quality are negatively affected by aphids. However, the defence mechanisms used by rose plants against aphids are unclear. Therefore, to understand the defence mechanism of rose under aphid stress, transcriptome and metabolome techniques were used to investigate the regulation mechanism in R. longicuspis infected with M. rosivorum.

RESULT

In our study, after inoculation with M. rosivorum, M. rosivorum quickly colonized R. longicuspis. A total of 34,202 genes and 758 metabolites were detected in all samples. Under M. rosivorum stress, R. longicuspis responded by MAPK cascades, plant hormone signal transduction pathway activation, RlMYBs and RlERFs transcription factors expression and ROS production. Interestingly, the 'brassinosteroid biosynthesis' pathway was significantly enriched in A3 d-vs.-A5 d. Further analysis showed that M. rosivorum induced the biosynthesis of secondary metabolites such as terpenoids, tannins and phenolic acids, among others. Importantly, the 'glutathione metabolic' and 'glucosinolate biosynthesis' pathways were significantly enriched, which involved in the rose against aphids.

CONCLUSION

Our study provides candidate genes and metabolites for Rosa defence against aphids. This study provides a theoretical basis for further exploring the molecular regulation mechanism of rose aphid resistance and aphid resistance breeding in the future.

Identification and Behavioral Assays of Alarm Pheromone in the Vetch Aphid Megoura viciae

Aphids are destructive pests, and alarm pheromones play a key role in their chemical ecology. Here, we conducted a detailed analysis of terpenoids in the vetch aphid, Megoura viciae, and its host plant Pisum sativum using gas chromatography/mass spectrometry. Four major components, (-)-β-pinene (49.74%), (E)-β-farnesene (32.64%), (-)-α-pinene (9.42%) and ( +)-limonene (5.24%), along with trace amounts of ( +)-sabinene, camphene and α-terpineol) (3.14%) were found in the aphid. In contrast, few terpenoids were found in the host plant, consisting mainly of squalene (66.13%) and its analog 2,3-epoxysqualene (31.59%). Quantitative analysis of the four major terpenes in different developmental stages of the aphid showed that amounts of the monoterpenes increased with increasing stage, while the sesquiterpene amount peaked in the 3rd instar. (-)-β-Pinene was the most abundant terpene at all developmental stages. Behavioral assays using a three-compartment olfactometer revealed that the repellency of single compounds varied in a concentration-dependent manner, but two mixtures [(-)-α-pinene: (-)-β-pinene: (E)-β-farnesene: ( +)-limonene = 1:44.4:6.5:2.2 or 1:18.4:1.3:0.8], were repellent at all concentrations tested. Our results suggest that (-)-α-pinene and (-)-β-pinene are the major active components of the alarm pheromone of M. viciae, but that mixtures play a key role in the alarm response. Our study contributes to the understanding of the chemical ecology of aphids and may help design new control strategies against this aphid pest.