Light intensity and spectral composition drive reproductive success in the marine benthic diatom Seminavis robusta

Gust Bilcke,Koen Sabbe,Klaas Vandepoele,Cristina Maria Osuna-Cruz,Alexandre Castagna,Wim Vyverman,Lore Van Craenenbroeck,Lieven De Veylder

doi:10.1038/s41598-021-92838-0

Gust Bilcke, Koen Sabbe + Show 6 more

Open Access

https://doi.org/10.1038/s41598-021-92838-0

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Abstract

The properties of incident light play a crucial role in the mating process of diatoms, a group of ecologically important microalgae. While species-specific requirements for light intensity and photoperiod have been observed in several diatom species, little is known about the light spectrum that allows sexual reproduction. Here, we study the effects of spectral properties and light intensity on the initiation and progression of sexual reproduction in the model benthic diatom Seminavis robusta. We found that distinct stages of the mating process have different requirements for light. Vigorous mating pair formation occurred under a broad range of light intensities, ranging from 10 to 81 µE m−2 s−1, while gametogenesis and subsequent stages were strongly affected by moderate light intensities of 27 µE m−2 s−1 and up. In addition, light of blue or blue–green wavelengths was required for the formation of mating pairs. Combining flow cytometric analysis with expression profiling of the diatom-specific cyclin dsCyc2 suggests that progression through a blue light-dependent checkpoint in the G1 cell cycle phase is essential for induction of sexual reproduction. Taken together, we expand the current model of mating in benthic pennate diatoms, which relies on the interplay between light, cell cycle and sex pheromone signaling.

Highlights

The properties of incident light play a crucial role in the mating process of diatoms, a group of ecologically important microalgae
Pheromone signaling is best understood in the benthic diatom S. robusta, where cells below the sexual size threshold (SST) signal their presence to the compatible mating type using sex inducing pheromones (SIP), initially resulting in a cell cycle arrest in the G1 p hase[10]
The formation of large cells in the centric Chaetoceros didymus was up to sevenfold higher under blue light compared to red light[50], while auxospores were only observed after red light treatment in the pennate H. ostrearia[45], suggesting that multiple independent light sensing mechanisms drive sexual reproduction in diatoms

Summary

Introduction

The properties of incident light play a crucial role in the mating process of diatoms, a group of ecologically important microalgae. We study the effects of spectral properties and light intensity on the initiation and progression of sexual reproduction in the model benthic diatom Seminavis robusta. Physiological evidence shows that the light regime can influence the progression of sex in both centric and pennate diatoms, even though the presence of a suitable partner has generally been considered the primary requirement for sexual reproduction in pennates[3]. The formation of large cells in the centric Chaetoceros didymus was up to sevenfold higher under blue light compared to red light[50], while auxospores were only observed after red light treatment in the pennate H. ostrearia[45], suggesting that multiple independent light sensing mechanisms drive sexual reproduction in diatoms. Physiological studies are fragmented and often fail to pinpoint the exact stages of the mating process that are susceptible to the light regime[3,43]

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