Characterising the early stages of diapause in Daphnia magna: a multi-omits approach

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Barnett, Rosemary Elizabeth (2019). Characterising the early stages of diapause in Daphnia magna: a multi-omits approach. University of Birmingham. Ph.D.

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Abstract

Diapause is a reversible developmental arrest in response to environmental challenges. The environmental genomics model organism Daphnia produces diapausing offspring. These dormant embryos produce healthy reproductive adults, even after 700 years of sustained developmental arrest. Despite this extraordinary adaptive feature of animal biology, prolonged diapause remained poorly understood. This thesis aims to develop Daphnia magna as a model system for embryonic diapause. I describe the reproducible induction of diapause in the laboratory and the development of embryos destined to diapause. My investigation reveals a delayed developmental trajectory compared to subitaneous embryos, until arrested at ca. 3500 cells. The collection and analysis of four omics datasets, including RNA sequencing paired with mass spectrometric data of the lipidome and metabolome, reveals distinct molecular differences during direct and diapause development. Furthermore, a significant developmental event is discovered by this molecular phenotyping of diapausing embryos at around 48 hours post-ovulation, when the molecular profiles are entirely different to pre-diapause, with changes manifesting later in the metabolome than the transcriptome. I identify additional molecular changes throughout the trajectory of diapause that are suggestive of molecular phenotypes describing the likely processes that produce an embryo that is capable of suspended animation for decades and even centuries.

Type of Work:

Thesis (Doctorates > Ph.D.)

Award Type:

Doctorates > Ph.D.

Supervisor(s):