A Metabolomics Exploration of the Sexual Phase in the Marine Diatom Pseudo-nitzschia multistriata.

Federica Fiorini,Mark Brönstrup,Maria Immacolata Ferrante,Camilla Borgonuovo

doi:10.3390/md18060313

Abstract

Pseudo-nitzschia multistriata is a planktonic marine diatom with a diplontic life cycle comprising a short sexual phase, during which gametes are produced following the encounter of two diploid cells of opposite mating type (MT). Gene expression studies have highlighted the presence of substantial changes occurring at the onset of sexual reproduction. Herein, we have hypothesized that the amount and nature of cellular metabolites varies along the mating process. To capture the metabolome of Pseudo-nitzschia multistriata at different harvesting times in an unbiased manner, we undertook an untargeted metabolomics approach based on liquid chromatography–tandem mass spectrometry. Using three different extraction steps, the method revealed pronounced differences in the metabolic profiles between control cells in the vegetative phase (MT+ and MT−) and mixed strains of opposite MTs (cross) undergoing sexual reproduction. Of the 2408 high-quality features obtained, 70 known metabolites could be identified based on in-house libraries and online databases; additional 46 features could be classified by molecular networking of tandem mass spectra. The reduction of phytol detected in the cross can be linked to the general downregulation of photosynthesis during sexual reproduction observed elsewhere. Moreover, the role of highly regulated compounds such as 7-dehydrodesmosterol, whose changes in abundance were the highest in the experiment, oleamide, ectoine, or trigonelline is discussed.

Highlights

Marine organisms produce a large variety of chemical compounds involved in several important processes like defense, intra- and inter- specific communication, sexual reproduction and feeding.These so-called secondary metabolites contribute to shaping aquatic communities and have a prominent ecological role [1]
Two strains of opposite mating type (MT) were grown as monocultures or mixed together to induce
Samples were grown in triplicate and collected h, h, and h after mixing their presence, are actively looking for a cell of opposite MT to pair with, or are forming gametes, therespectively two monocultures, in order to capturemetabolomics changes occurring theused cells to of detect each MT

Summary

Introduction

Marine organisms produce a large variety of chemical compounds involved in several important processes like defense, intra- and inter- specific communication, sexual reproduction and feeding. These so-called secondary metabolites contribute to shaping aquatic communities and have a prominent ecological role [1]. The growing interest in compounds deriving from marine organisms, which are relatively little explored and exploited, is motivated by the potential to discover new bioactive molecules [2]. Microalgae seem promising, since they can be grown on a large scale under indoor or outdoor conditions, and in principle allow sustained production of a given compound of interest using solar light without deplenishing natural resources.

Methods

Results

Conclusion