Biology subjects

Walt, H. K.

Publications and source records attributed to Walt, H. K..

6 recordsLinked to original sources

bioRxiv2024

Horizontally transferred glycoside hydrolase 26 may aid hemipteran insects in plant tissue digestion

Glycoside hydrolases are enzymes that break down complex carbohydrates into simple sugars by catalyzing the hydrolysis of glycosidic bonds. There have been multiple instances of adaptive horizontal gene transfer of genes belonging to various glycoside hydrolase families from microbes to insects, as glycoside hydrolases can metabolize constituents of the carbohydrate-rich plant cell wall. In this study, we characterize the horizontal transfer of a gene from the glycoside hydrolase family 26 (GH26) from bacteria to insects of the order Hemiptera. Our phylogenies trace the horizontal gene transfer to the common ancestor of the superfamilies Pentatomoidea and Lygaeoidea, which include stink bugs and seed bugs. After horizontal transfer, the gene was assimilated into the insect genome as indicated by the gain of an intron, and a eukaryotic signal peptide. Subsequently, the gene has undergone independent losses and expansions in copy number in multiple lineages, suggesting an adaptive role of GH26s in some insects. Finally, we measured tissue-level gene expression of multiple stink bugs and the large milkweed bug using publicly available RNA-seq datasets. We found that the GH26 genes are highly expressed in tissues associated with plant digestion, especially in the principal salivary glands of the stink bugs. Our results are consistent with the hypothesis that this horizontally transferred GH26 was co-opted by the insect to aid in plant tissue digestion and that this HGT event was likely adaptive.

evolutionary biology↗

bioRxiv2024

Detection of known and novel virus sequences in the black solider fly and expression of host antiviral pathways

Mass rearing of animals in close quarters can be highly conducive to microbe transmission, including pathogens. This has been shown multiple times in the case of important industrial insects such as crickets, silkworms, and honeybees. One industrial insect of increasing importance is the black soldier fly (Diptera: Hermetia illucens), as it can convert organic waste into high quality protein and fatty acids. Along with this, they take up far less space than traditional protein sources, as millions of black soldier flies can be reared in a relatively small facility. Because of this, there is a growing interest in the pathogens that could impact black soldier fly rearing efforts. So far, only three black soldier fly-associated viruses have been identified. We used metatranscriptomic sequencing to survey black soldier fly guts, frass, and diet for viruses. We detected sequences from two novel viruses. One, which we name Hermetia illucens sigma-like virus 1, is phylogenetically related to viruses of the genus Sigmavirus, which have been highly studied in Drosophila. The other novel virus, which we name Hermetia illucens toti-like virus 2, is the second toti-like virus to be described in the black soldier fly. We also detected two black soldier fly-associated viruses previously identified by our group: BSF nairo-like virus, and BSF uncharacterized bunya-like virus. Consistent with our previous study, these two viruses are found primarily in frass samples and occur together more often than expected at random. When analyzing host transcription, we found significant differences in gene expression for eight candidate antiviral genes in black soldier fly when comparing samples with and without viral sequences. Our results suggest that black soldier fly-virus interactions are ongoing, and they could be of interest to black soldier fly producers.

bioinformatics↗

bioRxiv2024

Under the radar: differential responses of bed bugs to an entomopathogen, environmental bacteria, and a human pathogen

BackgroundBed bugs (Hemiptera: Cimicidae) are a widely distributed, obligately blood-feeding insect, but they have never been linked to pathogen transmission in humans. Most other hematophagous insects that frequently bite humans transmit pathogens, and it is unclear why bed bugs do not. One hypothesis is that bed bugs have evolved a highly robust immune system because their mating system, traumatic insemination, exposes females to consistent wounding and bacterial infections. Although this has been proposed, very little is known about the bed bug immune system and how bed bugs respond to microbial challenges. Understanding the bed bug immune system could give insight to why bed bugs are not known to transmit disease and under what circumstances they could, while also facilitating biological control efforts involving microbes. MethodsTo investigate the immune response of bed bugs to bacterial challenges, we exposed female bed bugs to three bacterial challenges. 1.) Pseudomonas fluorescens, an entomopathogen known to have harmful effects to bed bugs, 2.) bacteria cultured from a bed bug enclosure likely encountered during traumatic insemination, and 3.) Borrelia duttoni, a human vector-borne pathogen that causes relapsing fever. We compared the transcriptomes of infected bed bugs with uninfected bed bugs, focusing on immune-related genes. We also conducted phylogenetic analyses to understand patterns of gene duplication and function of potentially immune-related genes. ResultsWe found many known immune effector genes upregulated in response to P. fluorescens and traumatic insemination-associated bacteria, but interestingly, not in response to B. duttoni. Furthermore, we found significant overlap in the genes differentially expressed in response to P. fluorescens and the traumatic insemination associated bacteria, and between P. fluorescens and B. duttoni, but no significant overlap between traumatic insemination bacteria and B. duttoni. We also show that bed bug diptericin-like antimicrobial peptides underwent a lineage-specific gene duplication, and that they may have further functional specialization. Finally, we identify previously overlooked candidates for future study of immune function in bed bugs, including some putative cuticle-associated genes, a laccase-like gene, and a mucin-like gene. ConclusionsBy taking comprehensive transcriptomic approach, our study is an important step in understanding how bed bugs respond to diverse immune challenges.

molecular biology↗

bioRxiv2023

Comparative genomics and the salivary transcriptome of the redbanded stink bug shed light on its high damage potential to soybean

The redbanded stink bug, Piezodorus guildinii (Westwood) (Hemiptera: Pentatomidae), is a significant soybean pest in the Americas, inflicting more physical damage on soybean than other native stink bugs. Studies suggest that its heightened impact is attributed to the aggressive digestive properties of its saliva. Despite its agricultural importance, the factors driving its greater ability to degrade plant tissues have remained unexplored in a genomic evolutionary context. In this study, we hypothesized that lineage-specific gene family expansions have increased the dosage of digestive genes expressed in the salivary glands. To investigate this, we annotated a previously published genome assembly of the redbanded stink bug and performed a comparative genomic analysis on 11 hemipteran species and reconstructed patterns of gene duplication, gain, and loss in the redbanded stink bug. We also performed RNA-seq on the redbanded stink bugs salivary tissues, along with the rest of the body without salivary glands. We identified hundreds of differentially expressed salivary genes, including a subset lost in other stink bug lineages but retained and expressed in the redbanded stink bugs salivary glands. These genes were significantly enriched with protein families involved in proteolysis, potentially explaining the redbanded stink bugs heightened damage to soybeans. Contrary to our hypothesis, we found no support for an increased dosage of digestive genes in the salivary glands of the redbanded stink bug. Nonetheless, these results provide insight into the evolution of this important crop pest, establishing a link between its genomic history and its agriculturally important physiology. SIGNIFICANCE STATEMENTThe redbanded stink bug, an important soybean pest in the Americas, inflicts greater damage to soybean due to higher salivary digestion. We employed comparative genomics and analyses of the salivary transcriptome to explore this and found that the differential retention of ancestral salivary genes may explain this phenomenon better than gene gains or duplications in the redbanded stink bug genome. We identify a distinct set of genes in the salivary gland that were differentially retained and expressed in the redbanded stink bug lineage, demonstrating enrichment in proteolytic function. This discovery offers a potential explanation for the redbanded stink bugs elevated damage to soybean crops.

genomics↗

bioRxiv2023

Do bed bugs transmit human viruses, or do humans transmit bed bug viruses? A worldwide survey of the bed bug RNA virosphere

Bed bugs (Hemiptera: Cimicidae) are a globally distributed hematophagous pest that routinely feed on humans. Unlike many blood-sucking arthropods, they have never been linked to disease transmission in a natural setting, and despite interest in their role as disease vectors, little is known about the viruses that bed bugs naturally harbor. Here, we present a global-scale survey of the bed bug RNA virosphere. We sequenced the metatranscriptomes of 22 individual bed bugs (Cimex lectularius and Cimex hemipterus) from 8 locations around the world. We detected sequences from two known bed bug viruses (Shuangao bedbug virus 1 and Shuangao bedbug virus 2) which extends their geographical range and the host range of Shuangao bedbug virus 1 to Cimex lectularius. We identified three novel bed bug virus sequences from a tenui-like virus (Bunyavirales), a toti-like virus (Ghabrivirales), and a luteo-like virus (Tolivirales). Interestingly, some of the bed bug viruses branch near to insect-transmitted plant-infecting viruses, opening questions regarding the evolution of plant virus infection. When we analyzed the putative viral sequences by their hosts collection location, we found unexpected patterns of geographical diversity that may reflect humans role in bed bug dispersal. Additionally, we investigated the effect that Wolbachia, the primary bed bug endosymbiont, may have on viral abundance and found that Wolbachia infection neither promotes nor inhibits viral infection. Finally, our results provide no evidence that bed bugs transmit any known human pathogenic viruses.

bioinformatics↗

bioRxiv2023

Bioinformatic Surveillance Leads to Discovery of Two Novel Putative Bunyaviruses Associated with Black Soldier Fly

The black soldier fly (Hermetia illucens, BSF) has emerged as an industrial insect of high promise because of its ability to convert organic waste into nutritious feedstock, making it an environmentally sustainable alternative protein source. As global interest rises, rearing efforts are also upscaled, which is highly conducive to pathogen transmission. Viral epidemics have stifled mass-rearing efforts of other insects of economic importance, such as crickets, silkworms, and honeybees, but little is known about the viruses that associate with BSF. Although it is thought that BSF are unusually resistant to pathogens because of their expansive antimicrobial gene repertoire, surveillance techniques could be useful to identify emerging pathogens and common BSF microbes. In this study, we used high-throughput sequencing data to survey BSF larvae and frass samples, and we identified two novel bunyavirus-like sequences. Our phylogenetic analyses grouped one in the family Nairoviridae, and the other with two unclassified bunyaviruses. We describe these putative novel viruses as BSF Nairovirus-like 1 and BSF uncharacterized bunyavirus-like 1. We identified candidate segments for the full BSF Nairovirus-like 1 genome using a technique based on transcript co-occurrence, and only a partial genome for BSF uncharacterized bunyavirus-like 1. These results emphasize the value of routine BSF colony surveillance and add to the number of viruses associated with BSF.

bioinformatics↗