The reproductive biology and venom system of the parasitoid wasp Nasonia vitripennis : a thesis presented in partial fulfilment of the requirements for the degree of Doctor of Philosophy in Genetics at Massey University, Manawatu, New Zealand
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Date
2019
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Massey University
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Abstract
Nasonia vitripennis (Nasonia) is a parasitoid wasp that uses a wide range of fly species
as hosts to support the growth and development of its offspring. This project focused on
two important aspects of Nasonia reproductive biology: (1) The role of the endosymbiont
Wolbachia pipientis (Wolbachia) in fertility and (2) the functional characteristics of the
venom system. The first part of the project focused on a bacterial endosymbiont
Wolbachia, which is found in high concentrations within the ovary and sperm cells of
Nasonia. As Wolbachia is maternally inherited, it manipulates host reproduction in ways
that favour the production of female offspring. In Nasonia, Wolbachia infection results in
the generation of reproductive cytoplasmic incompatibilities between infected and
uninfected wasps. As very little is known about the molecular mechanism used by
Wolbachia to interfere with Nasonia reproduction. RNA-seq was used to identify 84 and
58 genes differentially expressed in the ovary and testis, respectively, in response to
Wolbachia infection. RNA interference targeting differentially expressed genes was
unable to directly identify functional roles for these genes in cytoplasmic incompatibility,
suggesting that this mechanism may be regulated by co-expressed gene networks.
Unexpectedly, this study identified a Wolbachia gene (gene1092) that has been
incorporated into the Nasonia genome possibly by lateral gene transfer.
The second part of the project looked at the Nasonia venom system that has previously
been shown to contain a mixture of 79 peptides. The venom is introduced into the host
before egg laying and plays a role in altering the host’s physiology in ways that favour
development of the parasitoid’s progeny. However, the individual roles venom peptides
play in conferring these dramatic changes in the host have yet to be identified. Therefore,
RNA interference was used to target venom genes with the goal of better understanding
their function roles. Using this approach, it was shown that venom X and venom Z were
likely involved in arresting development in the host, while venom Y was likely to be
involved in modulating the host’s immune response. As the molecular pathways affected
by Nasonia venom underlie important cellular pathways, it is predicted that these venom
peptides could be developed into drugs to combat diseases such as cancer, hypertension
and diabetes.
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Figures re-used with permission.
Keywords
Nasonia, Reproduction, Venom, Genetics, Wolbachia