Transcriptomic Responses of Four Pelagophytes to Nutrient (N, P) and Light Stress

Yoonja Kang,Matthew J Harke,Jackie L Collier,Dianna L Berry,Steven W Wilhelm,Christopher J Gobler,Sonya T Dyhrman

doi:10.3389/fmars.2021.636699

Abstract

Pelagophytes are abundant picophytoplankton within open ocean ecosystems and the causative algae of harmful brown tide blooms in estuaries. The physiological capabilities facilitating the ecological success of pelagophytes in these diverse ecosystems remains poorly understood. Here, we investigated the transcriptional response of two coastal pelagophytes (Aureococcus anophagefferens and Aureoumbra lagunensis) and two open ocean pelagophytes (Pelagococcus subviridis and Pelagomonas calceolata) to conditions commonly found within the marine ecosystems where they thrive: low concentrations of nitrogen (N), phosphorus (P), or light. OrthoMCL was used to generate a total of 62,653 orthologous groups (OGs) with only a small fraction of these OGs (2,776 or 4.4%) being shared among all four pelagophytes. Of the commonly shared OGs, 8% were significantly differentially abundant under low N, P, or light with the majority associated with energy and lipid metabolism. Distinct responses among pelagophytes included increased abundance of transcripts encoding phosphate transporters (Aureococcus) and transcripts encoding a pyrophosphatase (Aureococcus and Pelagomonas) under low P, the expression of a suite of organic nitrogen-degrading enzymes under low N (Aureoumbra and Pelagomonas), increased abundance of transcripts encoding flavodoxins relative to ferredoxins (Pelagomonas) and transcripts encoding lysophospholipase (Pelagococcus) under low light, and both increases and decreases in abundance of transcripts encoding selenoproteins in all pelagophytes except Pelagococcus. Collectively, this study provides new information on the expressed gene compliment of these poorly characterized taxa and demonstrates that these pelagophytes possess a combination of shared and unique physiological features that likely facilitate their adaptation to distinct environmental conditions.

Highlights

Pelagophytes are important members of ocean plankton communities as they are numerically abundant and ubiquitously distributed across marine ecosystems (Simon et al, 1994; Andersen et al, 1996; John et al, 2007)
Aureococcus anophagefferens (CCMP1850 isolated from Great South Bay, NY, United States, 40.651◦N, −73.152◦W, in 1998) and Aureoumbra lagunensis (CCMP1510 isolated from Laguna Madre, TX, United States, 27.471◦N, −97.320◦W, in 1992), and two oceanic pelagophytes, Pelagococcus subviridis (CCMP1429 isolated from the subarctic Pacific, 49.917◦ N, −145.117◦, isolation date unknown) and Pelagomonas calceolata (CCMP1214 isolated from the subtropical Pacific, 30.833◦N, −136.833◦, in 1973), were used for experiments
The differentially abundant orthologous groups (OGs) were divided into three groups: OGs that were shared among all four pelagophytes, OGs that were found in two or three species, and OGs that were found in a single species

Summary

Introduction

Pelagophytes are important members of ocean plankton communities as they are numerically abundant and ubiquitously distributed across marine ecosystems (Simon et al, 1994; Andersen et al, 1996; John et al, 2007). Transcriptomic Responses of Four Pelagophytes harmful algal blooms (Aureococcus and Aureoumbra; Gobler and Sunda, 2012) and their prevalence in open ocean ecosystems (Pelagomonas and Pelagococcus; Lewin et al, 1977; Dupont et al, 2014). The bloom-forming pelagophytes Aureococcus anophagefferens and Aureoumbra lagunensis are notorious for their ability to form brown tides that damage shellfisheries and seagrass meadows and disrupt energy flow to upper trophic levels (Gobler and Sunda, 2012)

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Discussion

Conclusion