Degree Type

Dissertation

Date of Award

2019

Degree Name

Doctor of Philosophy

Department

Entomology

Major

Entomology

First Advisor

Russell A. Jurenka

Abstract

Sex pheromones play important roles in chemical communication, especially in the mating behavior of moths. Usually, sex pheromones are a blend of several compounds, mostly fatty acid derivatives, with C10-C18 carbon chain, with 0-4 double bonds, and an oxygenated functional group that could be alcohol, aldehyde, or acetate ester. The biosynthesis has been described and enzymes involved in the pathway include: the introduction of double bonds by fatty acyl desaturases, limited chain shortening by β-oxidation enzymes, functional group modification by fatty acyl-CoA reductases, fatty alcohol acetyltransferases and alcohol oxidases. Some genes have been functionally characterized in various moth species, but the genes encoding fatty alcohol acetyltransferases and alcohol oxidases have not been identified. I conducted the first study involving the identification of genes encoding fatty acyl-CoA reductase in Helicoverpa zea and fatty alcohol acetyltransferase in Trichoplusia ni. We screened the genes from the transcriptome of pheromone gland and tarsi in H. zea and designed experiments that included RT-PCR, qPCR, gene expression and functional assay in vitro, and RNAi in vivo to investigate the function. One gene encoding fatty acyl-CoA reductase was found involved in sex pheromone biosynthesis in pheromone gland and hexadecanal production in tarsi. In addition, this gene is distributed in tarsi as well, but is different from the pheromone gland specific FARs from other moths. The candidate acetyltransferase was selected due to homology with wax synthase. Unfortunately, it was present in all tissues and we did not find the function of acetylation to produce fatty acetate esters. More candidate genes need to be investigated and future work needs to be conducted to identify the acetyltransferase.

Mating disruption is a successful approach to control the world wide pest insect the pink bollworm moth utilizing the artificial sex pheromone, since it is environmentally friendly and effective. However, in Israel, the mating disruption technique is failing in some fields likely due to females producing a different ratio of sex pheromone components. We compared the transcriptome of pheromone gland from two populations, the lab which is never exposed to mating disruption and field populations which was exposed to mating disruption. We found some genes encoding desaturases, fatty acyl-CoA reductases, and putative acetyltransferases that were highly expressed in both populations, indicating they may be involved in the sex pheromone biosynthesis. However, none of them showed significant difference in abundance except two acetyltransferases. More research on acetyltransferases is needed to identify the ones involved in pheromone biosynthesis.

Also, we utilized the next generation sequencing technology to identify viruses. We used the transcriptome data from the pink bollworm and found some new single-stranded negative sense and positive sense RNA viruses. One iflavirus was present in pink bollworm from Israel and the USA in different life stages.

The research presented in this dissertation provides significant results using bioinformatics and molecular techniques to help understand pheromone biosynthesis in moths. It presents two transcriptome studies on the pheromone glands of two moths that produce acetate esters and aldehydes as the main pheromone components. It also presents an investigation into a fatty acyl-CoA reductase in the pheromone gland and tarsi both of which produce aldehyde pheromones. This research will provide deeper understanding on the molecular mechanism of sex pheromone biosynthesis.

Copyright Owner

Xiaoyi Dou

Language

en

File Format

application/pdf

File Size

203 pages

Included in

Entomology Commons

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