Hydrocarbons mediate seed dispersal: a new mechanism of vespicochory

Aristolochia mimics stink bugs to repel vertebrate herbivores via TRPA1 activation

Mimicry is the phenomenon in which one species (the mimic) closely resembles another (the model), enhancing its own fitness by deceiving a third party into interacting with it as if it were the model. In plants, mimicry is used primarily to gain fitness by withholding rewards from mutualists or deterring herbivores cost-effectively. While extensive work has been documented on putative defence mimicry, limited investigation has been conducted in the field of chemical mimicry. In this study, we used field experiments, chemical analyses, behavioural assays, and electrophysiology, to test the hypothesis that the birthwort Aristolochia delavayi employs chemical mimicry by releasing leaf scent that closely resembles stink bug defensive compounds and repels vertebrate herbivores. We show that A. delavayi leaf scent is chemically and functionally similar to the generalized defensive volatiles of stink bugs and that the scent effectively deters vertebrate herbivores, likely through the activation of TRPA1 channels via (E)-2-alkenal compounds. This study provides an unequivocal example of chemical mimicry in plants, revealing intricate dynamics between plants and vertebrate herbivores. Our study underscores the potency of chemical volatiles in countering vertebrate herbivory, urging further research to uncover their potentially underestimated importance.

Search for Snail Repellents: Antimollusc Activities from Stemona parviflora and Six Other Chinese Stemona Species

Snails are important agricultural pests difficult to control, but data regarding molluscicidal assays are scant. Stemona alkaloids are typical secondary metabolites for the taxa and have been broadly investigated for their pharmacological and toxicological effects. This makes it possible for us to further develop the toxicities of these compounds to snails. In this work, we tested the antifeedant properties of leaves from seven Chinese Stemona species against the land snail species Bradybaena ravida in choice and non-choice feeding assays. The tested leaves Stemona parviflora exhibited the most deterrent effects, and a further phytochemical investigation of aerial parts led to the identification of 16 alkaloids. Among them, three novel alkaloids could be identified. The alkaloidal fraction and single alkaloids were further assayed against this snail species, and the results suggest a cocktail effect because the impact of the alkaloidal fraction was higher than the effects caused by single alkaloids. The study can promote the search process of natural antimollusc products from plants to control snails.

Predator-prey encounters: deciphering the robbery relationship between highwayman flies and their ant victims

Examples of predator-prey interactions in which flies rob ants are uncommon. To date, this behavior has only been recorded in the genus Bengalia Robineau-Desvoidy (Bengaliinae, Diptera, Calliphoridae). These predatory flies ambush ants, and rob them of the food or offspring that they are carrying. However, because of the rarity of this behavior, the reasons and consequences (evolutionary advantages) are unknown, and indeed, the behavior has been sometimes considered anecdotal. In this study, we employed field investigations and behavioral analyses to investigate whether the sex of the fly Bengalia varicolor, or the weight and quality of the food carried by Pheidole nodus ants influenced fly-ant interactions in their natural habitats. We show that food weight and quality influenced the behavior of B. varicolor independent of the fly's sex. Robbing behavior by the flies was more successful when the food robbed was of high-quality and light in weight. Furthermore, the weight of the food robbed modulated the escape distance the flies could carry it. This then may affect the food quality and weight transported by the ants. This is a novel example of deciphering the relationship between highwayman flies and their ant victims. Given the widespread distribution of Bengalia flies, we suggest that such interspecific predator-prey encounters may shape the robbery interactions and the carrying behavior of further ant species in nature.

Dispersal modes affect Rhamnaceae diversification rates in a differentiated manner

The evolution of dispersal modes has been proposed to promote the diversification of angiosperms. However, little is known about the relative impact of different dispersal modes on plant diversification. We test the association between dispersal modes and diversification rates using Rhamnaceae, the cosmopolitan buckthorn family, as a model. We found that species with diplochory have the highest diversification rates followed by those with myrmecochory and ballistic dispersal, while lineages dispersed by vertebrates and wind have relatively low diversification rates. The difference in diversification rates may be closely linked to the difference in dispersal distance and ecological interactions implied by each dispersal mode. Species which disperse over larger geographical distances may have much higher speciation rates due to the increased chance of establishing isolated populations due to geological barriers or habitat fragmentation. However, long-distance dispersal may also increase the chance of extinction. By contrast, species with short-distance dispersal modes may have low speciation rates. Complex interactions with the surrounding environment may, however, impact diversification rates positively by increasing plant survival and reproductive success.

Camptothecin Effectively Regulates Germline Differentiation through Bam-Cyclin A Axis in Drosophila melanogaster

Camptothecin (CPT), first isolated from Chinese tree Camptotheca acuminate, produces rapid and prolonged inhibition of DNA synthesis and induction of DNA damage by targeting topoisomerase I (top1), which is highly activated in cancer cells. CPT thus exhibits remarkable anticancer activities in various cancer types, and is a promising therapeutic agent for the treatment of cancers. However, it remains to be uncovered underlying its cytotoxicity toward germ cells. In this study we found that CPT, a cell cycle-specific anticancer agent, reduced fecundity and exhibited significant cytotoxicity toward GSCs and two-cell cysts. We showed that CPT induced GSC loss and retarded two-cell cysts differentiation in a niche- or apoptosis-independent manner. Instead, CPT induced ectopic expression of a differentiation factor, bag of marbles (Bam), and regulated the expression of cyclin A, which contributed to GSC loss. In addition, CPT compromised two-cell cysts differentiation by decreasing the expression of Bam and inducing cell arrest at G1/S phase via cyclin A, eventually resulting in two-cell accumulation. Collectively, this study demonstrates, for the first time in vivo, that the Bam-cyclin A axis is involved in CPT-mediated germline stem cell loss and two-cell cysts differentiation defects via inducing cell cycle arrest, which could provide information underlying toxicological effects of CPT in the productive system, and feature its potential to develop as a pharmacology-based germline stem cell regulation agent.

Seed dispersal: Hungry hornets are unexpected and effective vectors

A new study finds that, in the forests of tropical China, hungry hornets are lured to the fruits of Aquilaria sinensis by highly volatile compounds structurally similar to volatiles from herbivore-damaged leaves. The hornets disperse the short-lived seeds rapidly to optimal new habitats.

Plant-defense mimicry facilitates rapid dispersal of short-lived seeds by hornets

Rates of seed dispersal have rarely been considered important. Here, we demonstrate through field observations and experiments that rapid dispersal is essential for the unusually short-lived seeds of Aquilaria sinensis (agarwood; Thymelaeaceae), which desiccate and die within hours of exposure by fruit dehiscence in the hot, dry forest canopy in tropical southwest China. We show that three species of Vespa hornets remove most seeds within minutes of exposure. The hornets consume only the fleshy elaiosomes and deposit most seeds in damp shade, where they can germinate, a mean of 166 m from the parent tree. Electrophysiological assays and field experiments demonstrate that the hornets are attracted by highly volatile short-carbon-chain (C5-C9) compounds, including aldehydes, ketones, alcohols, and acids, emitted from the dehiscent fruit capsule. These attractive fruit volatiles share 14 of 17 major electrophysiologically active compounds with those emitted from herbivore-damaged leaves, which attract predators, including hornets. Rapid seed dispersal thus appears to have been achieved in this species by the re-purposing of a rapid indirect defense mechanism. We predict that rapid seed dispersal by various mechanisms will be more widespread than currently documented and suggest that volatile attractants are more effective in facilitating this than visual signals, which are blocked by vegetation.

Assessment of the In Vivo and In Vitro Release of Chemical Compounds from Vespa velutina

Vespa velutina has been rapidly expanding throughout Galicia since 2012. It is causing human health risks and well-known losses in the beekeeping sector. Control methods are scarce, unspecific, and ineffective. Semiochemicals are insect-derived chemicals that play a role in communication and they could be used an integrated pest management tool alternative to conventional pesticides. A previous determination of the organic chemical profile should be the first step in the study of these semiochemicals. HS-SPME in living individuals and the sting apparatus extraction followed by GC-MS spectrometry were combined to extract a possible profile of these compounds in 43 hornets from Galicia. The identified compounds were hydrocarbons, ketones, terpenes, and fatty acid, and fatty acid esters. Nonanal aldehyde appeared in important concentrations in living individuals. While pentadecane, 8-hexyl- and ethyl oleate were mainly extracted from the venom apparatus. Ketones 2-nonanone, 2-undecanone and 7-nonen-2-one, 4,8-dimethyl- were identified by both procedures, as was 1,7-Nonadiene, 4,8-dimethyl-. Some compounds were detected for the first time in V. velutina such as naphthalene, 1,6-dimethyl-4-(1-methylethyl). The chemical profile by caste was also characterized.

Frugivorous birds disperse seeds of Ligustrum lucidum, seed-feeding weevils, and parasitic wasps of weevils via endozoochory

Seed dispersal by frugivorous birds is a famous plant-animal interaction. However, we demonstrated that frugivorous birds can disperse seeds of Ligustrum lucidum, and its seed parasite weevils and the parasitic wasps from the weevils in this study. The cryptic tetrad of Ligustrum-disperser-weevil-wasp may be an overlooked phenomenon in seed dispersal syndrome.

Evidence for the Involvement of the Chemosensory Protein AgosCSP5 in Resistance to Insecticides in the Cotton Aphid, Aphis gossypii

Simple Summary

Insect chemosensory proteins (CSPs) are potential targets for insect pest control strategies and are proposed to function in insect chemoreception, because they play a role in crop host location by binding and transporting odorant molecules. They are also thought to have other functions, for example, in tissue regeneration and in insecticide resistance, because they also express in nonolfactory tissues and are capable of binding insecticides. However, there are few reports that provide direct evidence for this proposal. In this study, we discovered gene gain-and-loss among aphid populations, possibly associated with different insecticide resistance, and then identified and cloned a CSP gene responsive to insecticide treatments. The introduction of such gene in Drosophila fruit flies made the transgenic flies less sensitive to the treatment of different insecticides. Our study advances the research of insect CSP functions and offers valuable new information to target CSPs for pest management.

Abstract

It has been speculated that insect chemosensory proteins (CSPs) may have additional roles beyond olfaction. In this study, the phylogenetic and genomic analyses of the CSPs of the cotton aphid, Aphis gossypii, revealed the presence of gene gain-and-loss among different aphid field populations. Differential expressions of eight CSP genes were demonstrated after treatments with insecticides of different modes of action. The expression of AgosCSP5 was significantly upregulated by the insecticide treatments in a dose-dependent manner. The Drosophila flies overexpressing AgosCSP5 were significantly less susceptible to the insecticides, omethoate, imidacloprid and cypermethrin but not to deltamethrin and tau-fluvalinate, compared with control flies. The transgenic Drosophila flies exhibited an LC₅₀ resistance ratio of 2.6 to omethoate, compared with control flies. Likewise, the mortality of the transgenic flies to imidacloprid and cypermethrin was significantly lower than that of the control flies (p < 0.01). Homology modelling, molecular docking and dynamic simulation supported the interactions and revealed a higher stability of AgosCSP5/insecticide complexes than AgosCSP5/semiochemical complexes. Our study demonstrates for first time the in vivo evidence for the involvement of CSP genes in insecticide resistance of crop insect pests and provides new insights of the newly discovered CSP-mediated insect resistance mechanism to insecticides.

A novel seed dispersal mode of Apostasia nipponica could provide some clues to the early evolution of the seed dispersal system in Orchidaceae

Despite being one of the most diverse families, scant attention has been paid to the seed dispersal system in Orchidaceae, owing to the widely accepted notion that wind dispersal is the dominant strategy. However, the indehiscent fruits, with seeds immersed in fleshy tissue, evoke the possibility of endozoochory in Apostasioideae, the earliest diverging lineage of orchids. In the present study, I investigated the seed dispersal system of Apostasia nipponica by direct observation, time-lapse photography, and investigation of the viability of seeds passing through the digestive tract of orthopterans. This study revealed a previously undocumented seed dispersal system in A. nipponica, in which the cricket, Eulandrevus ivani, and the camel cricket, Diestrammena yakumontana, consume the fruit and defecate viable seeds. Orthopterans are rarely considered seed dispersers, but the gross fruit morphology and pigmentation patterns of some Apostasia species parallel those seen in A. nipponica, suggesting that similar seed dispersal systems could be widespread among Apostasia species. Whether seed dispersal by orthopteran frugivores is common in Apostasioideae warrants further investigation.

Oviposition Deterrents in Larval Frass of Potato Tuberworm Moth, Phthorimaea operculella (Lepidoptera: Gelechiidae)

The potato tuberworm moth (PTM) Phthorimaea operculella (Zeller) (Lepidoptera: Gelechiidae) is one of the most damaging pests of potato Solanum tuberosum L. in warm temperate and subtropical areas. Our previous experiment showed that extracts of larval frass of PTM deterred oviposition of conspecific females. In this study, we investigated the identification of chemicals in larval frass that were influencing the oviposition of PTM by behavioral bioassays and electroantennography analysis in the laboratory. Frass was collected from third and fourth instar larvae and combined analysis of gas chromatography coupled with electroantennography (GC-EAD) of dichloromethane extracts showed that eight compounds from larval frass extracts elicited repeatable antennal responses from mated females. Seven EAD-active compounds in frass volatile extract were identified by gas chromatography-mass spectrometry (GC-MS) as linoleic acid, octadecanoic acid, tricosane, pentacosane, heptacosane, nonacosane, and cholesterol. Oviposition bioassays indicated that frass extracts had a deterrent effect on egg laying, the deterrent activity increased with the concentration of frass extracts, and the threshold value for statistical significance in oviposition deterrence was in the range of 20-200 mg frass per cage. Linoleic acid, pentacosane, heptacosane, nonacosane, and cholesterol in larval frass volatiles were found to play a key role in repelling oviposition in a dose-dependent manner. We suggest that the bioactive compounds in larval frass are responsible for repelling oviposition of PTM, and n-alkanes, especially pentacosane, strongly deter oviposition and may be considered as a potential oviposition deterrent for potential applications.

The role of botanical gardens in scientific research, conservation, and citizen science

Plant diversity is currently being lost at an unprecedented rate, resulting in an associated decrease in ecosystem services. About a third of the world's vascular plant species face the threat of extinction due to a variety of devastating activities, including, over-harvesting and over exploitation, destructive agricultural and forestry practices, urbanization, environmental pollution, land-use changes, exotic invasive species, global climate change, and more. We therefore need to increase our efforts to develop integrative conservation approaches for plant species conservation. Botanical gardens devote their resources to the study and conservation of plants, as well as making the world's plant species diversity known to the public. These gardens also play a central role in meeting human needs and providing well-being. In this minireview, a framework for the integrated missions of botanical gardens, including scientific research, in/ex situ conservation, plant resource utilization, and citizen science are cataloged. By reviewing the history of the development of Kunming Botanical Garden, we illustrate successful species conservation approaches (among others, projects involving Camellia, Rhododendron, Magnolia, Begonia, Allium, Nepenthes, medicinal plants, ornamental plants, and Plant Species with Extreme Small Populations), as well as citizen science, and scientific research at Kunming Botanical Garden over the past 80 years. We emphasize that Kunming Botanical Garden focuses largely on the ex situ conservation of plants from Southwest China, especially those endangered, endemic, and economically important plant species native to the Yunnan Plateau and the southern Hengduan Mountains. We also discuss the future challenges and responsibilities of botanical gardens in a changing world, including: the negative effects of outbreeding and/or inbreeding depression; promoting awareness, study, and conservation of plant species diversity; accelerating global access to information about plant diversity; increasing capacity building and training activities. We hope this minireview can promote understanding of the role of botanical gardens.