Embryo development and sex determination in the Cassava whitefly (Bemisia tabaci)

Corkill, Rebecca (2019) Embryo development and sex determination in the Cassava whitefly (Bemisia tabaci). Doctoral thesis, University of East Anglia.

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Abstract

The cassava whitefly, Bemisia tabaci (Hemiptera: Aleyrodidae), is a highly invasive and destructive
agricultural pest, with a global distribution. B. tabaci insect has evolved resistance to multiple
insecticides, and therefore, new control methods will have to be developed to control this insect.
The self-limiting system, which produces a female-specific lethal heritable element and causes
population suppression, works well for control of mosquitoes. The goal of this thesis is to assess
the feasibility of creating a self-limiting system in B. tabaci.
The self-limiting system requires generating transgenic insects, and this is done via injection of
constructs into eggs at the pre-germ-line cell stage (around blastoderm formation), this enables
stable germline transformation. However, there has been limited research into B. tabaci early
embryogenesis stages, and therefore it is unclear when transformation constructs will have to be
introduced. In this thesis, I conducted confocal microscopy studies to determine the timing of
early embryogenesis stages in B. tabaci MED. Unexpectedly, I revealed that early embryogenesis
in B. tabaci starts before the eggs are oviposited, unlike in mosquitoes and fruitflies. Therefore,
injecting laid B. tabaci eggs is too late for obtaining stable transgenic whitefly lines, though
somatic transgenics may be obtained.
Past self-limiting transgenic insects used genes found in the sex determination pathway, for
female-specific lethality, as these were expressed early and had sex-specific splicing. Genes of the
sex determination pathways in B. tabaci and other hemipteran are largely unknown. Hence, I
conducted a genome-wide search of 11 publicly available hemipteran genomes to identify their
sex determination genes. Also, I conducted single-embryonic RNA-seq experiments in B. tabaci to
assess if these genes undergo sex-specific splicing at the early embryogenesis stages in males and
females. These results identified sex determination genes in B. tabaci and other hemipterans and
revealed potential targets for future genetic control methods.

Item Type:	Thesis (Doctoral)
Faculty \ School:	Faculty of Science > School of Biological Sciences
Depositing User:	Katherine Whittaker
Date Deposited:	14 Feb 2020 16:30
Last Modified:	14 Feb 2020 16:30
URI:	https://ueaeprints.uea.ac.uk/id/eprint/74205
DOI:

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