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Title: Ascaroside-induced neuronal reprogramming of the germline in the nematode Auanema freiburgensis
Author: Zuco, Giuseppina
ISNI:       0000 0004 7967 4840
Awarding Body: University of Warwick
Current Institution: University of Warwick
Date of Award: 2017
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This thesis examines the response of the trioecious nematode Auanema freiburgensis to environmental cues leading to an increase of hermaphrodite sex-phenotype in the offspring. It is shown that A. freiburgensis hermaphrodite mothers produce a higher fraction of hermaphrodite progeny if exposed to crowded conditions, and by sampling secretions (supernatant) of dense A. freiburgensis cultures this shift can be induced in vitro with individual worms. The signal from the supernatant is sensed by an amphid neuron that is exposed to the environment, which is revealed by laser ablation of the neuron, after which the supernatant effect disappears. With the aim to understand how the signal is passed to the progeny, RNAseq (for small RNAs) and histone-methylation immunostaining were conducted. In these experiments, it was found that small RNAs that potentially silence genes involved in epigenetic DNA modification are regulated upon supernatant exposure of the mother nematode, and the immunostaining revealed that this correlates with a change in histone modification of the developing oocytes in the pre-meiotic tip of the mother's gonad, hence affecting the progeny germline. The results from this study suggest that crowding cues sensed by an A. freiburgensis hermaphrodite mother are translated into an epigenetic information passed to the offspring, leading to a larger fraction of hermaphrodite progeny. Every hermaphrodite goes through a starvation-resistant larval stage named dauer. Thus, environmental signals received by the mother indicating imminent overcrowding, and thus lack of food, may be of adaptive value. While the mechanism of epigenetic signal transmission in A. freiburgensis is not finally revealed, the results presented here are in accordance with descriptions of "maternal effects" and "intergenerational inheritance".
Supervisor: Not available Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID:  DOI: Not available
Keywords: QH426 Genetics