The role of lipid-modified proteins in cell wall synthesis and signaling.

The plant cell wall is a complex and dynamic extracellular matrix. Plant primary cell walls are the first line of defense against pathogens and regulate cell expansion. Specialized cells deposit a secondary cell wall that provides support and permits water transport. The composition and organization of the cell wall varies between cell types and species, contributing to the extensibility, stiffness, and hydrophobicity required for its proper function. Recently, many of the proteins involved in the biosynthesis, maintenance, and remodeling of the cell wall have been identified as being post-translationally modified with lipids. These modifications exhibit diverse structures and attach to proteins at different sites, which defines the specific role played by each lipid modification. The introduction of relatively hydrophobic lipid moieties promotes the interaction of proteins with membranes and can act as sorting signals, allowing targeted delivery to the plasma membrane regions and secretion into the apoplast. Disruption of lipid modification results in aberrant deposition of cell wall components and defective cell wall remodeling in response to stresses, demonstrating the essential nature of these modifications. Although much is known about which proteins bear lipid modifications, many questions remain regarding the contribution of lipid-driven membrane domain localization and lipid heterogeneity to protein function in cell wall metabolism. In this update, we highlight the contribution of lipid modifications to proteins involved in the formation and maintenance of plant cell walls, with a focus on the addition of glycosylphosphatidylinositol anchors, N-myristoylation, prenylation, and S-acylation.

The association between mitochondrial genetic variation and reduced colony fitness in an invasive wasp.

Despite the mitochondrion's long-recognized role in energy production, mitochondrial DNA (mtDNA) variation commonly found in natural populations was assumed to be effectively neutral. However, variation in mtDNA has now been increasingly linked to phenotypic variation in life history traits and fitness. We examined whether the relative fitness in native and invasive common wasp (Vespula vulgaris) populations in Belgium and New Zealand (NZ), respectively, can be linked to mtDNA variation. Social wasp colonies in NZ were smaller with comparatively fewer queen cells, indicating a reduced relative fitness in the invaded range. Interestingly, queen cells in this population were significantly larger leading to larger queen offspring. By sequencing 1,872 bp of the mitochondrial genome, we determined mitochondrial haplotypes and detected reduced genetic diversity in NZ. Three common haplotypes in NZ frequently produced many queens, whereas the four rare haplotypes produced significantly fewer or no queens. The entire mitochondrial genome for each of these haplotypes was sequenced to identify polymorphisms associated with fitness reduction. We found 16 variable sites; however, no nonsynonymous mutation that was clearly causing impaired mitochondrial function was detected. We discuss how detected variants may alter secondary structures, gene expression or mito-nuclear interactions, or could be associated with nuclear-encoded variation. Whatever the ultimate mechanism, we show reduced fitness and mtDNA variation in an invasive wasp population as well as specific mtDNA variants associated with fitness variation within this population. Ours is one of only a few studies that confirm fitness impacts of mtDNA variation in wild nonmodel populations.

Draft genomes of Paenibacillus larvae isolated from honeybee colonies (Apis mellifera) in Fiji.

Here, we report draft genomic sequences from three Paenibacillus larvae isolates, the causative agent of American Foulbrood (AFB), obtained from honeybee colonies of Apis mellifera in Fiji, which allow both enterobacterial repetitive intergenic consensus and multilocus sequence typing genotypes to be elucidated for Fijian AFB.

Genomic analysis of the population structure of Paenibacillus larvae in New Zealand.

New Zealand is a remote country in the South Pacific Ocean. The isolation and relatively late arrival of humans into New Zealand has meant there is a recorded history of the introduction of domestic species. Honey bees (Apis mellifera) were introduced to New Zealand in 1839, and the disease American foulbrood was subsequently found in the 1870s. Paenibacillus larvae, the causative agent of American foulbrood, has been genome sequenced in other countries. We sequenced the genomes of P. larvae obtained from 164 New Zealand apiaries where American foulbrood was identified in symptomatic hives during visual inspection. Multi-locus sequencing typing (MLST) revealed the dominant sequence type to be ST18, with this clonal cluster accounting for 90.2% of isolates. Only two other sequence types (with variants) were identified, ST5 and ST23. ST23 was only observed in the Otago area, whereas ST5 was limited to two geographically non-contiguous areas. The sequence types are all from the enterobacterial repetitive intergenic consensus I (ERIC I) genogroup. The ST18 and ST5 from New Zealand and international P. larvae all clustered by sequence type. Based on core genome MLST and SNP analysis, localized regional clusters were observed within New Zealand, but some closely related genomes were also geographically dispersed, presumably due to hive movements by beekeepers.

Pathogenicity and virulence of bacterial strains associated with summer mortality in marine mussels (Perna canaliculus).

The occurrence of pathogenic bacteria has emerged as a plausible key component of summer mortalities in mussels. In the current research, four bacterial isolates retrieved from moribund Greenshell࣪ mussels, Perna canaliculus, from a previous summer mortality event, were tentatively identified as Vibrio and Photobacterium species using morpho-biochemical characterization and MALDI-TOF MS and confirmed as V. celticus, P. swingsii, P. rosenbergii, and P. proteolyticum using whole genome sequencing. These isolates were utilized in a laboratory challenge where mussels were injected with cell concentrations ranging from 105 to 109 CFU/mussel. Of the investigated isolates, P. swingsii induced the highest mortality. Additionally, results from quantitative polymerase chain reaction analysis, focusing on known virulence genes were detected in all isolates grown under laboratory conditions. Photobacterium rosenbergii and P. swingsii showed the highest expression levels of these virulence determinants. These results indicate that Photobacterium spp. could be a significant pathogen of P. canaliculus, with possible importance during summer mortality events. By implementing screening methods to detect and monitor Photobacterium concentrations in farmed mussel populations, a better understanding of the host-pathogen relationship can be obtained, aiding the development of a resilient industry in a changing environment.

A Diverse Viral Community from Predatory Wasps in Their Native and Invaded Range, with a New Virus Infectious to Honey Bees.

Wasps of the genus Vespula are social insects that have become major pests and predators in their introduced range. Viruses present in these wasps have been studied in the context of spillover from honey bees, yet we lack an understanding of the endogenous virome of wasps as potential reservoirs of novel emerging infectious diseases. We describe the characterization of 68 novel and nine previously identified virus sequences found in transcriptomes of Vespula vulgaris in colonies sampled from their native range (Belgium) and an invasive range (New Zealand). Many viruses present in the samples were from the Picorna-like virus family (38%). We identified one Luteo-like virus, Vespula vulgaris Luteo-like virus 1, present in the three life stages examined in all colonies from both locations, suggesting this virus is a highly prevalent and persistent infection in wasp colonies. Additionally, we identified a novel Iflavirus with similarity to a recently identified Moku virus, a known wasp and honey bee pathogen. Experimental infection of honey bees with this novel Vespula vulgaris Moku-like virus resulted in an active infection. The high viral diversity present in these invasive wasps is a likely indication that their polyphagous diet is a rich source of viral infections.

High-Quality Assemblies for Three Invasive Social Wasps from the Vespula Genus.

Social wasps of the genus Vespula have spread to nearly all landmasses worldwide and have become significant pests in their introduced ranges, affecting economies and biodiversity. Comprehensive genome assemblies and annotations for these species are required to develop the next generation of control strategies and monitor existing chemical control. We sequenced and annotated the genomes of the common wasp (Vespula vulgaris), German wasp (Vespula germanica), and the western yellowjacket (Vespula pensylvanica). Our chromosome-level Vespula assemblies each contain 176-179 Mb of total sequence assembled into 25 scaffolds, with 10-200 unanchored scaffolds, and 16,566-18,948 genes. We annotated gene sets relevant to the applied management of invasive wasp populations, including genes associated with spermatogenesis and development, pesticide resistance, olfactory receptors, immunity and venom. These genomes provide evidence for active DNA methylation in Vespidae and tandem duplications of venom genes. Our genomic resources will contribute to the development of next-generation control strategies, and monitoring potential resistance to chemical control.

A metatranscriptomic analysis of diseased social wasps (Vespula vulgaris) for pathogens, with an experimental infection of larvae and nests.

Social wasps are a major pest in many countries around the world. Pathogens may influence wasp populations and could provide an option for population management via biological control. We investigated the pathology of nests of apparently healthy common wasps, Vespula vulgaris, with nests apparently suffering disease. First, next-generation sequencing and metatranscriptomic analysis were used to examine pathogen presence. The transcriptome of healthy and diseased V. vulgaris showed 27 known microbial phylotypes. Four of these were observed in diseased larvae alone (Aspergillus fumigatus, Moellerella wisconsensis, Moku virus, and the microsporidian Vavraia culicis). Kashmir Bee Virus (KBV) was found to be present in both healthy and diseased larvae. Moellerella wisconsensis is a human pathogen that was potentially misidentified in our wasps by the MEGAN analysis: it is more likely to be the related bacteria Hafnia alvei that is known to infect social insects. The closest identification to the putative pathogen identified as Vavraia culicis was likely to be another microsporidian Nosema vulgaris. PCR and subsequent Sanger sequencing using published or our own designed primers, confirmed the identity of Moellerella sp. (which may be Hafnia alvei), Aspergillus sp., KBV, Moku virus and Nosema. Secondly, we used an infection study by homogenising diseased wasp larvae and feeding them to entire nests of larvae in the laboratory. Three nests transinfected with diseased larvae all died within 19 days. No pathogen that we monitored, however, had a significantly higher prevalence in diseased than in healthy larvae. RT-qPCR analysis indicated that pathogen infections were significantly correlated, such as between KBV and Aspergillus sp. Social wasps clearly suffer from an array of pathogens, which may lead to the collapse of nests and larval death.

Single-stranded RNA viruses infecting the invasive Argentine ant, Linepithema humile.

Social insects host a diversity of viruses. We examined New Zealand populations of the globally widely distributed invasive Argentine ant (Linepithema humile) for RNA viruses. We used metatranscriptomic analysis, which identified six potential novel viruses in the Dicistroviridae family. Of these, three contigs were confirmed by Sanger sequencing as Linepithema humile virus-1 (LHUV-1), a novel strain of Kashmir bee virus (KBV) and Black queen cell virus (BQCV), while the others were chimeric or misassembled sequences. We extended the known sequence of LHUV-1 to confirm its placement in the Dicistroviridae and categorised its relationship to closest relatives, which were all viruses infecting Hymenoptera. We examined further for known viruses by mapping our metatranscriptomic sequences to all viral genomes, and confirmed KBV, BQCV, LHUV-1 and Deformed wing virus (DWV) presence using qRT-PCR. Viral replication was confirmed for DWV, KBV and LHUV-1. Viral titers in ants were higher in the presence of honey bee hives. Argentine ants appear to host a range of' honey bee' pathogens in addition to a virus currently described only from this invasive ant. The role of these viruses in the population dynamics of the ant remain to be determined, but offer potential targets for biocontrol approaches.