Biology subjects

Shelby, E. A.

Publications and source records attributed to Shelby, E. A..

3 recordsLinked to original sources

bioRxiv2024

Embryological insights into the evolution of genome regulation using haploid and diploid whiteflies, Bemisia tabaci

The whitefly, Bemisia tabaci, is a hemipteran with a haplodiploid sex determination system, which provides a natural experiment for examining genome function in haploid and diploid embryos. Yet the embryogenesis of B. tabaci remains understudied. Our previous work has established a possible role of DNA methyltransferase 1 (Dnmt1) in genome stability. In this study we used maternal RNA interference (RNAi) and immunohistochemistry to study the complex dynamics between DNMT1 and ploidy during embryogenesis. We found that both haploid and diploid B. tabaci have a similar developmental timeline to other holometabolous insects. We also found that, like other obligatory haploid insects, ploidy does not affect developmental timing, suggesting that maternal factors play a greater role than ploidy in developmental timing. For embryos with reduced expression of Dnmt1, we found that the loss of DNMT1 disrupts blastoderm development and affects nuclei morphology in both haploid and diploid embryos. Our results suggest that DNMT1 is required for blastoderm development.

developmental biology↗

bioRxiv2023

Dmnt1 and Wnt in the production of oocytes

The function of methylation in insects and the DNA methyltransferase (Dnmt) genes that influence methylation remains uncertain. We used RNAi to reduce the gene expression of Dnmt1 within the whitefly Bemisia tabaci, a hemipteran species that relies on Dnmt1 for proper gametogenesis. We then used RNA-seq to test an a priori hypothesis that meiosis related genetic pathways would be perturbed. We generally did not find an overall effect on meiosis related pathways. However, we found that genes in the Wnt pathway, genes associated with the entry into meiosis in vertebrates, were differentially expressed. Our results are consistent with Dnmt1 knockdown influencing specific pathways and not causing general transcriptional response. This is a finding that is also seen with other insect species. We also characterized the methylome of B. tabaci and assessed the influence of Dnmt1 knockdown on cytosine methylation. This species has methylome characteristics comparable to other hemipterans regarding overall level, enrichment within gene bodies, and bimodal distribution of methylated/non-methylated genes. Very little differential methylation was observed, and difference of methylation were not associated with differences of gene expression. The effect on Wnt presents an interesting new candidate pathway for future studies.

genomics↗

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↗