Biology subjects

Cunningham, C. B.

Publications and source records attributed to Cunningham, C. B..

7 recordsLinked to original sources

bioRxiv2026

Conserved genes with variable expression and function: Vasa, Piwi, and Dnmt1 in Oncopeltus fasciatus gametogenesis

The production of gametes is one of the universal processes of life and given millennia of evolution many of the core genes involved are expected to be highly refined and resistant to change. Here we examine the pattern of expression and functionally characterize three genes widely involved in gametogenesis: Vasa, Piwi, and Dnmt1. We examine their cellular location during both oogenesis and spermatogenesis in Oncopeltus fasciatus, a hemipteran insect, using fluorescent in situ hybridization chain reaction. In females, expression of Piwi was restricted to the trophocytes, but Vasa and Dnmt1 were expressed in developing ooctyes as well as the trophoctyes. In males, Piwi was expressed in the testis germline stem cells (GSCs), but Vasa and Dnmt1 expression was absent from these cells. Additionally, Piwi and Vasa were expressed in secondary spermatogonia and spermatocytes while Dnmt1 was predominantly expressed in the primary spermatogonia. We also functionally characterized their necessity for gametogenesis after RNAi-mediated gene expression knockdown. Vasa was not required for oogenesis but was required during spermatogenesis. Piwi and Dnmt1 were required for both oogenesis and spermatogenesis. These results were in contrast to their requirement for these processes from other organisms, which highlight the unexpected variation found in the processes and suggest that conservation depends on the level at which genes are examined: sequence, expression, or phenotypic and biochemical function. This suggests there is a more nuanced evolutionary story of conserved, yet plastic, gametogenic gene set in Metazoa that deserves further study across more organisms.

evolutionary biology↗

bioRxiv2023

The critical role of Dmnt1 during spermatogenesis is not predictable, but knockdown does cause pervasive differential transcription.

Cytosine methylation and its machinery influence the gene expression of many eukaryotes; however, insects are an exception to this general tenet despite many lineages retaining methyltransferases and methylated genomes. Here, we tested the a priori hypothesis that perturbed genetic pathways will be associated with meiosis using transcriptomics because previous our work using Oncopeltus fasciatus shows that gametogenesis is interrupted at meiosis following knockdown of DNA methyltransferase 1 (Dnmt1). Testes, which are almost exclusively contain gametes at varying stages of development, were sampled at 7-days and 14-days following knockdown of Dmnt1 using RNAi. Using microscopy, we found actively dividing spermatocysts were reduced at both sampling points. However, we found limited support of perturbation for our predicted cell cycle and meiotic pathways and only at 14-days. We found that Gene Ontology terms had no preferential enrichment for meiosis-associated genes. Following our a priori tests, we used the full dataset to uncover further candidate pathways influenced by Dnmt1 knockdown. Very few genes were differentially expressed at 7-days, but nearly half were at 14-days. We did not find strong candidate pathways for how Dnmt1 knockdown was achieving its effect through Gene Ontology term overrepresentation analysis. Given the evidence from microscopy, we propose Dnmt1 knockdown results in condensed nuclei after mitosis-meiosis transition and then cellular arrest. This explanation posits that differential gene expression is a product of comparing healthy to arrested cells and is not a targeted response.

genomics↗

bioRxiv2022

Flexible parental care ensures robustness of post-embryonic development

The evolutionary repercussions of parental effects are often discussed as static effects that can have negative influences on offspring fitness that may even persist across generations. However, individuals are not passive recipients and may mitigate the persistence of parental effects through their behaviour. Here, we tested how the burying beetle Nicrophorus orbicollis, a species with complex parental care, responded to poor parenting. We manipulated the duration of parental care received and measured the impact on traits of both F1 and F2 offspring. As expected, reducing parental care negatively affected traits that are ecologically important for burying beetles, including F1 offspring development time and body size. However, F1 parents that received reduced care as larvae spent more time feeding F2 offspring than parents that received full care as larvae. As a result, both the number and mass of F2 offspring were unaffected by the developmental experience of their parents. Our results show that flexible parental care may be able to overcome poor developmental environments and limit negative parental effects to a single generation.

evolutionary biology↗

bioRxiv2021

Patterns of parent and offspring gene expression reflect canalization, not plasticity, in response to environmental stress

Parenting is thought to evolve to buffer offspring from variable, unpredictable, and challenging environmental conditions. In the subsocial carrion beetle, Nicrophorus orbicollis, stressful temperatures during parenting do not affect parental behavior despite imposing steep fitness costs to parents. Here, we ask if plasticity of gene expression underpins this behavioral stability or facilitates independent compensation by larvae. To test this we characterized gene expression of parents and offspring before and during active parenting under benign (20{degrees}C) and stressful (24{degrees}C) temperatures to identify genes of parents and offspring associated with thermal response, parenting/being parented, and gene expression plasticity associated with behavioral stability of parental care. The main effects of thermal and social condition each shaped patterns of gene expression in females, males, and larvae. In addition, we implicated 79 genes in females as buffering parental behavior across environments. The majority of these underwent significant changes in expression in actively parenting mothers at the benign temperature, but not at the stressful temperature. Our results suggest that neither genetic programs for parenting nor their effects on offspring gene expression are fundamentally different under stressful conditions, and that behavioral stability is associated primarily with the maintenance of existing genetic programs rather than replacement or supplementation. Thus, while selection for compensatory gene expression could expand the range of thermal conditions parents will tolerate, without expanding the toolkit of genes involved selection is unlikely to lead to adaptive changes of function.

evolutionary biology↗

bioRxiv2017

Changes Of Gene Expression But Not Cytosine Methylation Are Associated With Behavioural Plasticity Of Parental Care

Behaviour is often on the front line of plasticity in response to different environments. At the genetic level, behavioural changes are likely to be associated with changes of gene expression. Most studies to date have focused on gene expression differences associated with discrete behavioural states reflecting development or age-related changes, such as honey bee castes. However, more rapidly flexible behaviour is often observed in response to social context or simple individual variation. The differences in genetic influences for the different forms of plasticity are poorly understood. In this study we contrasted gene expression during male parental care of the burying beetle, Nicrophorus vespilloides, in a factorial design. Male N. vespilloides males typically do not provide care when females are present. However, male care is inducible by the removing female and has parental effects equivalent to female care. We used this experimental manipulation to isolate gene expression and cytosine methylation associated with differences of behavioural state, differences of social context, or differences of individual flexibility for expressing care. The greatest number of differentially expressed genes was associated with behavioural state, followed by differences of social contexts, and lastly differences of individual variation. DNA methylation has been hypothesized to regulate the transcriptional architecture that regulates behavioural transitions. We tested this hypothesis by quantifying differences of cytosine methylation that were associated with differences of behavioural state and individual flexibility. Changes of cytosine methylation were not associated with changes of gene expression. Our results suggest a hierarchical association between gene expression and the different sources of variation that influence behaviour, but that this process is not controlled by DNA methylation despite reflecting levels of plasticity in behaviour. Our results further suggest that the extent that a behaviour is transient plays an underappreciated role in determining the molecular mechanisms that underpin the behaviour.

genetics↗

bioRxiv2017

Duplication And Sub/Neofunctionalization Of malvolio, An Insect Homolog Of Nramp, In The Subsocial Beetle Nicrophorus vespilloides

Gene duplication has long been thought to play a facilitating role in evolution. With growing numbers of sequenced genomes, increasing numbers of duplicate genes are uncovered with unknown functions. Here we examine malvolio, a gene involved in heavy metal transport but that also affects behavior in honey bees and Drosophila. There is only one copy of malvolio in honey bees and Drosophila despite its different roles. A phylogenetic analysis in insects suggests that malvolio has duplicated multiple times in different orders. To test if the two copies might have different functions, we examined expression levels of malvolio in brain, fat bodies, Malpighian tubules, midgut, ovaries, testes and thoracic musculature in the beetle Nicrophorus vespilloides. We found that mvl1 was expressed in all tissues, with highest expression in fat bodies and relatively lower expression in testes, Malpighian tubules, and brain, and ovaries. Expression of mvl2 differed, with significant expression only seen in brain and midgut. Because malvolio has been implicated in behavior, and these beetles have highly developed parenting behavior, we next examined expression during different behavioral states including virgin, mating, preparing resources for offspring, feeding offspring and post care. We found differing expression patterns for the two copies, with mvl1 increasing in expression during resource preparation and feeding offspring, and mvl2 decreasing in these same states. Given these patterns of expression, we suggest that malvolio in N. vespilloides has experienced sub/neofunctionalization following its duplication, and is evolving differing and tissue-specific roles in behavior and physiology.

evolutionary biology↗

bioRxiv2017

The transcriptional basis of quantitative behavioral variation

What causes individuals to produce quantitatively different phenotypes? While substantial research has focused on the allelic changes that affect phenotype, we know less about how gene expression accompanies variable phenotypes. Here, we investigate the transcriptional basis of variation in parental provisioning using two species of burying beetle, Nicrophorus orbicollis and Nicrophorus vespilloides. Specifically, we used RNA-seq to compare the transcriptomes of parents that provided high amounts of provisioning behavior versus low amounts in males and females of each species. We found that there were no overarching transcriptional patterns that distinguish high from low caring parents, and no informative transcripts that displayed particularly large expression differences in females or males. However, we did find more subtle gene expression changes between high and low provisioning parents that are consistent across sexes as well as between the two species. Furthermore, we show that transcripts previously implicated in transitioning into parental care in N. vespilloides had high variance in the levels of transcription and were unusually likely to display differential expression between high and low provisioning parents. Thus, quantitative behavioral variation appears to reflect many transcriptional differences of small effect. We show that nuanced regulation of the same gene products that are required for the transition of one behavioral state to another are also those influencing variation within a behavioral state.\n\nAuthor SummaryBurying beetles in the genus Nicrophorus breed on vertebrate carcasses and provide advanced parental care to their offspring by regurgitating partially digested flesh. However, all adult beetles do not uniformly express this trait. Some provide a large amount of parenting to their offspring, and some only a little. Here, we investigate the genetic causes of why some Nicrophorus beetles feed their offspring more than others. We demonstrate that this difference is likely caused by many small changes in gene expression, rather than a few genes that have major effects. We also find that some of the same genes that help to turn on parental care behavior in burying beetles also seem to play a role in determining how much care a beetle gives. These results provide new angles on longstanding questions about the complexity of the mechanisms that underlie quantitative variation in populations.

genetics↗