Comparative Structural and Functional Analyses of the Fusiform, Oval, and Triradiate Morphotypes of Phaeodactylum tricornutum Pt3 Strain

Abstract

The diatom Phaeodactylum tricornutum is a marine unicellular microalga that exists under three main morphotypes: oval, fusiform, and triradiate. Previous works have demonstrated that the oval morphotype of P. tricornutum Pt3 strain presents specific metabolic features. Here, we compared the cellular organization of the main morphotypes of the diatom P. tricornutum Pt3 strain through transmission electron and advanced light microscopies. The three morphotypes share similarities including spectral characteristics of the plastid, the location of the nucleus, the organization of mitochondria around the plastid as well as the existence of both a F-actin cortex, and an intracellular network of F-actin. In contrast, compared to fusiform and triradiate cells, oval cells spontaneously release proteins more rapidly. In addition, comparison of whole transcriptomes of oval versus fusiform or triradiate cells revealed numerous differential expression of positive and negative regulators belonging to the complex dynamic secretory machinery. This study highlights the specificities occurring within the oval morphotype underlying that the oval cells secrete proteins more rapidly.

Multiplexed Genome Editing via an RNA Polymerase II Promoter-Driven sgRNA Array in the Diatom Phaeodactylum tricornutum: Insights Into the Role of StLDP

“…Furthermore, oval and circular cells were amply present in cultures of the edited lines, and they formed cell clumps. It is known that P. tricornutum cells secrete exopolymeric substances (EPS) with adhesive properties, particularly the oval cells ( Willis et al, 2013 ; Galas et al, 2021 ). It has also been suggested that oval cells represent a form that is more resilient to stresses, in Galas et al (2021) and references therein.…”

Comparative Proteomic Analysis of the Diatom Phaeodactylum tricornutum Reveals New Insights Into Intra- and Extra-Cellular Protein Contents of Its Oval, Fusiform, and Triradiate Morphotypes

“…Phaeodactylum tricornutum cell cultures enriched in one dominant morphotype: Fusiform, Oval, and Triradiate were used in this work. Such cultures have been characterized recently using TEM and confocal microscopies ( Ovide et al, 2018 ; Galas et al, 2021 ). Especially, the latest study demonstrated that the three morphotypes share similarities in terms of organelle localization (nucleus, mitochondria, F-actin cortex, intracellular network, etc.).…”

“…Especially, the latest study demonstrated that the three morphotypes share similarities in terms of organelle localization (nucleus, mitochondria, F-actin cortex, intracellular network, etc.). In contrast, compared to fusiform and triradiate cells, oval cells spontaneously release proteins more rapidly, underlying a more rapid protein secretion in the oval morphotype ( Galas et al, 2021 ). In the present study, we analyzed through proteomic the intracellular proteins and secreted proteins from the different morphotypes issues from the same Pt3 strain ( Figure 1 ).…”

“…SW was then complemented with a nutrient medium (Conway 1 mL/L) and a metasilicate sodium solution (80 mg/L) ( Ovide et al, 2018 ). Typical confocal and transmission electron microscopy (TEM) images of each morphotype can be found in Ovide et al (2018) and Galas et al (2021) . In this work, the cultures were non-axenic.…”

“…Recently, Song et al (2020) also reported that the oval cells synthesized a higher amount of proteins and pigments compared to the fusiform cells while the fusiform cell cultures accumulated lipids and carbohydrates. In addition, Galas and collaborators have shown that the oval Pt3 cells of P. tricornutum are secreted proteins more rapidly than the fusiform and triradiate Pt3 cells ( Galas et al, 2021 ).…”