Mating type specific transcriptomic response to sex inducing pheromone in the pennate diatomSeminavis robusta

Abstract

Sexual reproduction is a fundamental phase in the life cycle of most diatoms. Despite its role as a source of genetic variation, it is rarely reported in nature and its molecular foundations remain largely unknown.Here, we integrate independent transcriptomic datasets, in order to prioritize genes responding to sex inducing pheromones (SIPs) in the pennate diatom Seminavis robusta. We observe marked gene expression changes associated with SIP treatment in both mating types, including an inhibition of S-phase progression, chloroplast division, mitosis and cell wall formation. Meanwhile, meiotic genes are upregulated in response to SIP, including a sexually induced diatom specific cyclin (dsCyc). Our data further suggest an important role for reactive oxygen species, energy metabolism and cGMP signaling during the early stages of sexual reproduction. In addition, we identify several genes with a mating type specific response to SIP, and link their expression pattern with physiological responses such as the production of the attraction pheromone diproline and mate-searching behaviour in MT+. Combined, our results provide a model for early sexual reproduction in pennate diatoms and significantly expand the suite of target genes to detect sexual reproduction events in natural diatom populations.

Diurnal transcript profiling of the diatomSeminavis robustareveals adaptations to a benthic lifestyle

“…The pellet was fixated by adding 10 mL of ice cold 75% ethanol, after which samples were kept in the dark at 4 °C. Preparation of samples, staining with SYBR green and flow cytometry analysis on a Bio-Rad S3e cell sorter was performed as detailed by Bilcke et al (2020). In parallel, cell density and the proportion of cytokinetic cells were determined at each time point from microscopic pictures taken with a Canon Powershot G11 camera mounted on a Primovert inverted microscope at 20x magnification.…”

“…In culture, S. robusta cells display typical benthic behaviour, including surface attachment, biofilm formation and vigorous gliding motility, which has been exploited to study chemotaxis [31]. Cultures from strain 85A have been popular for transcriptomics experiments [32,33,34,35]. This strain is a fifth generation lineage from the S. robusta laboratory pedigree whose ancestral clones originate from subtidal sediments of the Veerse Meer in The Netherlands (51°32'36" N, 3°48'15" E) [36,37].…”

Altering the Sex Pheromone Cyclo(l-Pro-l-Pro) of the Diatom Seminavis robusta towards a Chemical Probe

“…The physiological concentration of the pheromone is 100 nM. ( D ) Cell size restitution: mating is followed by pairing of gametangial cells, gamete formation and fusion, followed by expansion of the zygotes into two auxospores which subsequently germinate to produce a large vegetative cell each [ 7 , 9 , 10 , 11 ].…”

“…Regardless of the broad occurrence of these cyclopeptides, their receptors are not extensively characterized. Bilcke et al [ 11 ] found that in S. robusta MT + genes encoding for transmembrane proteins were upregulated in response to SIP − , suggesting that a G protein-coupled receptor (GPCR) is responsible for the perception of 1 .…”

Pheromone Mediated Sexual Reproduction of Pennate Diatom Cylindrotheca closterium

“…In the planktonic diatom P. multistriata a pheromone is suggested to synchronize the sexual events (Scalco et al 2014) whereas three different consecutively induced pheromones are thought to be involved in the reproduction of the freshwater diatom Pseudostaurosira trainorii to control sexualization of cells and orientate gametes (Sato et al 2011). Mating of S. robusta was studied intensively and is also promoted by three distinct pheromones (Bilcke et al 2020;Bondoc et al 2019Bondoc et al , 2016Chepurnov et al 2002). Two sex inducing pheromones SIP + and SIPare produced by mt + and mt − , respectively, and synchronize the cell cycle (Moeys et al 2016).…”