Investigating evolution of innate immunity in insects: focus on two signaling pathways Público
Kumi-Ansu, Yaw (Spring 2018)
Abstract
Innate immunity is the primary intrinsic immune response in invertebrates, whereas vertebrates are equipped with both innate and acquired immunity. For this project, I sought to investigate the evolution of innate immunity in two signaling pathways: Toll and Immune deficiency (IMD). In the IMD pathway, we investigated the pattern of loss of peptidoglycan recognition proteins (PGRP) in Insecta, and whether this may be linked to homology (loss restricted to a monophyletic cluster) or convergent evolution (independently arising trait). This was achieved by building a presence-absence profile of 173 species, of which 12 showed putative loss of PGRPs. We observed a combination of both types of loss, with Hemipterans (true bugs) displaying a distinct paraphyletic loss of PGRPs in sub-order Sternorrhyncha. Independently arising loss was found in some species flies and beetles. Endosymbiosis was a common trait among most of the species that showed putative loss, but a few species also hint at the possibility of adaptations to an extreme environment contributing to the loss of PGRPs. In the Toll pathway, we focused on signatures of selection of Toll-like receptor (TLR) genes in different populations of monarch butterflies. We hypothesized that trends in signatures of selection would be influenced by variations across populations based on prevalence of their natural protozoan parasite (Ophryocyctis elektroschirrha) and coexistence with different host plant communities of milkweed. Specifically, some milkweed species contain varying concentrations of toxic cardenolides which reduce disease burden from O. elektroschirrha in adults who fed on these as larvae. We hypothesized that there would be a difference in signatures of selection in immunity-related TLRs between the North American population which encounters lower parasite prevalence and toxic cardenolide concentration relative to other global populations. Alignment and construction of a phylogeny from TLRs sequences identified in monarchs and a few other species revealed two main types of clustering: intra- and interspecific clustering of TLRs for the species studied. Our investigation of signatures of selection via Tajima’s D, revealed that our hypothesis was refuted since there wasn’t a distinct trend between the North American population and the others regarding the signatures of selection of the TLRs.
Table of Contents
Introduction…………………………………………………………………………….…..1
Chapter 1 | The presence and absence of peptidoglycan recognition proteins in Insecta….2
Background…………...…………………………………………………………………....2
Methodology…………………………………………………………………………….....4
Results…………………………………………………………………………..……….....7
Discussion………………………………………………………………………..………..13
Chapter 2 | Toll-like receptor genes in Monarchs…………………………………………17
Background…………………...……………………………..………………………….....17
Methodology………………………………………………………………..……………..21
Results…………………………………………………………………..………………....23
Discussion……………………………………………………………..…………………..29
Conclusion………………………………………………………………………………....32
References Cited…………………………………..……………………………………….33
About this Honors Thesis
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Primary PDF
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Investigating evolution of innate immunity in insects: focus on two signaling pathways () | 2018-04-10 03:34:32 -0400 |
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Supplemental Files
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Sequences used in study (Accession IDs and sequences for proteins and nucleotides) | 2018-04-10 03:34:29 -0400 |
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