Nitric oxide mediates oxylipin production and grazing defense in diatoms.

Nitric oxide mediates oxylipin production and grazing defense in diatoms.

Environ Microbiol. 2019 Nov 28;:

Authors: Johnson MD, Edwards BR, Beaudoin DJ, Van Mooy BAS, Vardi A

Abstract
Diatom blooms are important features of productive marine ecosystems and are known to support higher trophic levels. However, when stressed or wounded, diatoms can produce oxylipin molecules known to inhibit the reproduction and development of copepods and decrease microzooplankton growth rates. Using oxylipin chemical treatments, lipidomic analysis, and functional genomic approaches, we provide evidence that nitric oxide (NO) and oxylipin signaling pathways in diatoms respond to protist grazers, resulting in increased defense fitness and survival. Exposure of the diatom Phaeodactylum tricornutum to the dinoflagellate Oxyrrhis marina resulted in NO production by P. tricornutum, and pronounced change in its dissolved oxylipin profile. Experimentally elevating levels of NO also resulted in increased oxylipin production, and lower overall grazing rates. Further, O. marina preferentially grazed on P. tricornutum prey with lower levels of NO, suggesting that this molecule and its effect on oxylipin pathways play a key role in prey selection. Exposure of O. marina grazing on P. tricornutum to exogenous oxylipins also decreased grazing rates, which is consistent with a grazing deterrence role for these molecules. These results suggest that NO and oxylipin production help to structure diatom communities, in part by modulating interactions with microzooplankton predators. This article is protected by copyright. All rights reserved.

PMID: 31782207 [PubMed – as supplied by publisher]