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Title: Stress responses of the marine diatom Skeletonema spp. to polyunsaturated aldehydes (PUAS)
Author: Gallina, Alessandra Alexia
ISNI:       0000 0004 2746 2109
Awarding Body: Open University
Current Institution: Open University
Date of Award: 2012
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Diatom-derived polyunsaturated aldehydes (PUAs) are secondary metabolites acting as teratogens against grazers, allelochemicals by inhibiting the growth of closeby phytoplankton species, and also as signal molecules to determine the cell fate of diatom populations. The work presented here focuses on Nitric Oxide (NO) and Reactive Oxygen Species (ROS) production in response to PUAs in Skeletonema marinoi, a cosmopolitan, bloom forming and PUA-producing diatom species. In the first part of the thesis I addressed the problem of whether PUA-producing species might have evolved different stress response mechanisms with respect to non-PUA producing ones and if this may r underlie their different ecological success. S. marinoi was exposed to different PUAs: DECA, which is not produced by S. marinoi, OCTA and HEPTA, which are PUAs commonly produced by this diatom and a mixture of these last two (MIX). A reduction in NO production was observed in response to all PUAs tested, probably due to consumption of physiological levels of NO, possibly indicating that this messanger acts as a growth regulator under optimal growth conditions. In the second part, a comparison with the non-PUA producing diatom Phaeodactylum tricornutum revealed different reactions to the same PUAs (i.e. DECA), with an increase in NO production in DECA-exposed P. tricornutum, whereas in response to OCTA a reduction in NO production was evident. Thus, NO production in response to PUAs appears to be both PUA-specific and species-specific. Additionally, S. marinoi cells exposed to the photoinhibitor DCMU presented an increase in NO production, indicating that NO production in S. marinoi is likely to be also stress specific.
Supervisor: Not available Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral