Tineola bisselliella, the webbing clothes moth, is an economically important, globally distributed, synanthropic pest species. Tineola bisselliella is a member of Tineidae, the fungus moth family, which is a basal moth lineage in Lepidoptera. They are facultatively keratinophagous and can digest both keratin and detritus. The mechanism of keratin digestion has mostly been investigated from a symbiotic lens and is specifically thought to be performed by Bacillus bacterium that have been found in the gut of T. bisselliella larvae. However, expression of candidate digestion genes postulated to be in the genome have also been hypothesized as a probable mechanism. Here, we present the first draft de novo reference genome assembly and annotation for this species to investigate of the presence of keratin digestion genes, chromosomal synteny, and the evolution of the ancestral karyotype. Our final pseudochromosome-level assembly, which was assembled using syntenic comparisons with the closely related species Tinea pellionella, is 243.630 Mb and has an N50 length of 8.708 Mb.
To facilitate quality genome annotation, we sequenced, assembled, and annotated a transcriptome. The annotated transcriptome had 13,615 protein-coding genes, while the final annotated genome contains 11,267 genes; 10,769 genes were functionally identified. We also performed systematic synteny comparisons of our T. bisselliella genome assembly and other basal moths and butterflies to investigate chromosome evolution. Comparison of synteny conservation between Melitea cinxia, which possesses the ancestral lepidopteran karyotype, and Tineola bisselliella suggests small fragmentation and fusion events were the mechanism by which Tineola bisselliella’s karyotype was reduced. This contrasts observations in other Lepidoptera with reduced karyotypes (e.g., Heliconius melpomene), which have undergone whole chromosomal fusion events.
Finally, we performed preliminary differential gene expression and gene ontology enrichment analyses to investigate the adaptation of the ability to digest keratin in this organism. Tineola bisselliella adults do not ingest or digest food; therefore, we hypothesized genes related to keratin digestion would be enriched in larvae when compared to adults. Differential expression analysis of RNA sequencing data revealed 5,066 genes significantly differentially expressed between larval and adult stages out of 39,404 genes in the assembled and annotated transcriptome. GO enrichment analysis of differentially expressed genes revealed significant enrichment of GO terms associated with DNA replication in adults and enrichment of GO terms associated with serine proteases, oxidative-reduction reaction enzymes, and other proteases in larvae. Depletion of GO terms related to DNA replication in larvae suggest they were experiencing a nutrient poor environment when reared in the lab and entered larval diapause to slow their development and conserve energy. Our observations are consistent with previous research that found DNA replication was slowed in other Lepidoptera during diapause. Our data also illustrates in larvae digesting keratin, GO terms associated with serine proteases and oxidative-reduction reaction enzymes as well as other proteases are enriched. This suggests they are involved in the digestion process of keratin. However, this does not rule out that symbiotic bacteria that express keratinases are also part of this process. Future experiments should include differential expression and GO enrichment analyses with a larger sample size to confirm the results we obtained. Additionally functional experiments should be performed to investigate the expression of serine proteases, oxidative-reduction reaction enzymes, and other proteases in larvae in the absence of symbionts to determine if these ancestral digestion genes were able to facilitate the transition to a facultative keratin diet.
| Identifer | oai:union.ndltd.org:bu.edu/oai:open.bu.edu:2144/48244 |
| Date | 26 February 2024 |
| Creators | Alqassar, Jasmine Donna |
| Contributors | Mullen, Sean P. |
| Source Sets | Boston University |
| Language | en_US |
| Detected Language | English |
| Type | Thesis/Dissertation |
| Rights | Attribution 4.0 International, http://creativecommons.org/licenses/by/4.0/ |
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