Finding a partner in the ocean: molecular and evolutionary bases of the response to sexual cues in a planktonic diatom

Swaraj Basu, Shrikant Patil, Daniel Mapleson, Monia Teresa Russo, Laura Vitale, Cristina Fevola, Florian Maumus, Raffaella Casotti, Thomas Mock, Mario Caccamo, Marina Montresor, Remo Sanges, Maria Immacolata Ferrante

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Abstract

Microalgae play a major role as primary producers in aquatic ecosystems. Cell signalling regulates their interactions with the environment and other organisms, yet this process in phytoplankton is poorly defined. Using the marine planktonic diatom Pseudo-nitzschia multistriata, we investigated the cell response to cues released during sexual reproduction, an event that demands strong regulatory mechanisms and impacts on population dynamics.

We sequenced the genome of P. multistriata and performed phylogenomic and transcriptomic analyses, which allowed the definition of gene gains and losses, horizontal gene transfers, conservation and evolutionary rate of sex-related genes. We also identified a small number of conserved noncoding elements.

Sexual reproduction impacted on cell cycle progression and induced an asymmetric response of the opposite mating types. G protein-coupled receptors and cyclic guanosine monophosphate (cGMP) are implicated in the response to sexual cues, which overall entails a modulation of cell cycle, meiosis-related and nutrient transporter genes, suggesting a fine control of nutrient uptake even under nutrient-replete conditions.

The controllable life cycle and the genome sequence of P. multistriata allow the reconstruction of changes occurring in diatoms in a key phase of their life cycle, providing hints on the evolution and putative function of their genes and empowering studies on sexual reproduction.
Original languageEnglish
Pages (from-to)140–156
Number of pages17
JournalNew Phytologist
Volume215
Issue number1
Early online date21 Apr 2017
DOIs
Publication statusPublished - Jul 2017

Keywords

  • algae
  • diatom
  • genomics
  • mating type
  • phytoplankton
  • Pseudo-nitzschia multistriata
  • sexual reproduction
  • signal transduction

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