Lipidomics reveals how the endoparasitoid wasp Pteromalus puparum manipulates host energy stores for its young

Lipidomic features of honey bee and colony health during limited supplementary feeding

Honey bee nutritional health depends on nectar and pollen, which provide the main source of carbohydrates, proteins and lipids to individual bees. During malnutrition, insect metabolism accesses fat body reserves. However, this process in bees and its repercussions at the colony level are poorly understood. Using untargeted lipidomics and gene expression analysis, we examined the effects of different feeding treatments (starvation, sugar feeding and sugar + pollen feeding) on bees and correlated them with colony health indicators. We found that nutritional stress led to an increase in unsaturated triacylglycerols and diacylglycerols, as well as a decrease in free fatty acids in the bee fat body. Here, we hypothesise that stored lipids are made available through a process where unsaturations change lipid's structure. Increased gene expression of three lipid desaturases in response to malnutrition supports this hypothesis, as these desaturases may be involved in releasing fatty acyl chains for lipolysis. Although nutritional stress was evident in starving and sugar-fed bees at the colony and physiological level, only starved colonies presented long-term effects in honey production.

Genome of the parasitoid wasp Cotesia chilonis sheds light on amino acid resource exploitation

Background

A fundamental feature of parasitism is the nutritional exploitation of host organisms by their parasites. Parasitoid wasps lay eggs on arthropod hosts, exploiting them for nutrition to support larval development by using diverse effectors aimed at regulating host metabolism. However, the genetic components and molecular mechanisms at the basis of such exploitation, especially the utilization of host amino acid resources, remain largely unknown. To address this question, here, we present a chromosome-level genome assembly of the parasitoid wasp Cotesia chilonis and reconstruct its amino acid biosynthetic pathway.

Results

Analyses of the amino acid synthetic pathway indicate that C. chilonis lost the ability to synthesize ten amino acids, which was confirmed by feeding experiments with amino acid-depleted media. Of the ten pathways, nine are known to have been lost in the common ancestor of animals. We find that the ability to synthesize arginine was also lost in C. chilonis because of the absence of two key genes in the arginine synthesis pathway. Further analyses of the genomes of 72 arthropods species show that the loss of arginine synthesis is common in arthropods. Metabolomic analyses by UPLC-MS/MS reveal that the temporal concentrations of arginine, serine, tyrosine, and alanine are significantly higher in host (Chilo suppressalis) hemolymph at 3 days after parasitism, whereas the temporal levels of 5-hydroxylysine, glutamic acid, methionine, and lysine are significantly lower. We sequence the transcriptomes of a parasitized host and non-parasitized control. Differential gene expression analyses using these transcriptomes indicate that parasitoid wasps inhibit amino acid utilization and activate protein degradation in the host, likely resulting in the increase of amino acid content in host hemolymph.

Conclusions

We sequenced the genome of a parasitoid wasp, C. chilonis, and revealed the features of trait loss in amino acid biosynthesis. Our work provides new insights into amino acid exploitation by parasitoid wasps, and this knowledge can specifically be used to design parasitoid artificial diets that potentially benefit mass rearing of parasitoids for pest control.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12915-022-01313-3.

Non-targeted lipidomics and transcriptomics analysis reveal the molecular underpinnings of mandibular gland development in Apis mellifera ligustica

The mandibular gland is an important exocrine gland of worker bees, which mainly secretes fatty acids and pheromones. Lipids have important roles in energy storage, membrane structure stabilization, and signaling. However, molecular underpinnings of mandibular gland development and lipid remodeling at the different physiological stages of worker bees is still lacking. In this study, we used scanning and transmission electron microscopy to reveal the morphological changes in secretory cells, and liquid chromatography-mass spectrometry and RNA-seq to investigate the lipidome and gene transcripts during development. The morphology of secretory cells was flat in newly emerged workers, becoming vacuolated and turgid when they were activated in nurse bees and foragers. Transport vesicles became denser from newly emerged bees to 21-day worker bees. Concentrations of 10-HDA reached a maximum within 15d workers and changes in genes expression were consistent with 10-HDA content. Non-targeted lipidomics analysis of newly emerged, 6d, and 15d worker bees revealed that PC and TAG were the main lipids in mandibular gland, and lipids dramatically altered across developmental stages. TAG 54:4 was increased most strongly at 6d and 15d worker bees, meanwhile, the abundances of TAG 54:1 and TAG 54:2 were decreased sharply. Further, transcriptomics analysis showed that differentially expressed genes were significantly enriched in key nutrient metabolic pathways, particularly lipid metabolism, in 6d and 15d bees. This multi-omic perspective provides a unique resource and deeper insight into bee mandibular gland development and baseline data for further study of the mandibular gland in worker bees.

Symbiotic bracovirus of a parasite manipulates host lipid metabolism via tachykinin signaling

Parasites alter host energy homeostasis for their own development, but the mechanisms underlying this phenomenon remain largely unknown. Here, we show that Cotesia vestalis, an endoparasitic wasp of Plutella xylostella larvae, stimulates a reduction of host lipid levels. This process requires excess secretion of P. xylostella tachykinin (PxTK) peptides from enteroendocrine cells (EEs) in the midgut of the parasitized host larvae. We found that parasitization upregulates PxTK signaling to suppress lipogenesis in midgut enterocytes (ECs) in a non-cell-autonomous manner, and the reduced host lipid level benefits the development of wasp offspring and their subsequent parasitic ability. We further found that a C. vestalis bracovirus (CvBV) gene, CvBV 9–2, is responsible for PxTK induction, which in turn reduces the systemic lipid level of the host. Taken together, these findings illustrate a novel mechanism for parasite manipulation of host energy homeostasis by a symbiotic bracovirus gene to promote the development and increase the parasitic efficiency of an agriculturally important wasp species.

Parasitic wasps are ubiquitous on earth and diverse. They lay eggs in or on the bodies of their hosts, and they have evolved adaptive strategies to regulate the energy metabolism of their hosts to match their own specific nutrition requirements. Here, we found that Cotesia vestalis, a solitary endoparasitoid of Plutella xylostella, uses symbiotic bracovirus as a weapon to manipulate host systemic lipid levels. Specifically, a C. vestalis bracovirus (CvBV) gene, CvBV 9–2, is responsible for the induction of PxTK, which in turn suppresses lipogenesis in the midgut of the parasitized host, leading to a nutritional lipid level suitable for the development and subsequent parasitic efficiency of C. vestalis wasps. Our study provides innovative insights into the mechanisms by which parasitic wasps manipulate host lipid homeostasis and may help to expand our knowledge of other parasitic systems.