Adhesion molecules from the diatom Phaeodactylum tricornutum (Bacillariophyceae): genomic identification by amino‐acid profiling and in vivo analysis

Abstract

Cell adhesion molecules (CAMs) are important in prokaryotes and eukaryotes for cell-cell and cell-substratum interactions. The characteristics of adhesive proteins in the model diatom Phaeodactylum tricornutum were investigated by bioinformatic analysis and in vivo characterization. Bioinformatic analysis of the protein coding potential of the P. tricornutum genome used an amino-acid profile that we developed as a new system to identify uncharacterized or novel CAMs. Putative diatom CAMs were identified and seven were characterized in vivo, by generation of transgenic diatom lines overexpressing genes encoding C-terminal yellow fluorescent protein (YFP) fusion proteins. Three of these selected genes encode proteins with weak similarity to characterized proteins, a c-type lectin and two fasciclins, whereas the others are novel. The resultant cell lines were investigated for alterations in their adhesive ability. Whole cell-substratum adhesion strength was measured in a fully turbulent flow chamber, while atomic force microscopy was used to quantify the relative frequency of adhesion, as well as the length and strength of single molecules in the secreted mucilage. Finally, quartz crystal microbalance analysis characterized the visco-elastic properties and interaction of the mucilage-substratum interface. These combined studies revealed a range of phenotypes affecting adhesion, and led to the identification of candidate proteins involved in diatom adhesion. In summary, our study has for the first time combined bioinformatics and molecular physiological studies to provide new insights into diatom adhesive molecules.

Identifying metabolic pathways for production of extracellular polymeric substances by the diatomFragilariopsis cylindrusinhabiting sea ice

“…This reaction must be catalysed by an (yet) unidentified enzyme, since Man is an important constituent of diatom EPS, particularly in lower-solubility structural EPS [ 35 , 81 ]. The pathway for synthesizing UDP- N -acetylglucosamine, which is used for the production of glycoproteins which contribute to folding and adhesion properties in diatom EPS [ 33 ], and homologues of two cell adhesion molecules previously identified in P. tricornutum [ 33 ], were up-regulated in F. cylindrus during under temperature and salinity stress.…”

“…cylindrus genome ( http://genome.jgi.doe.gov/Fracy1/ ) using GO, KEGG pathways and clusters of eukaryotic orthologous groups (KOG) of proteins [ 64 ] information. Additionally, using canonical polysaccharide biosynthesis pathways [ 29 , 65 ] and bibliographic resources for phylogenetically close organisms [ 1 , 29 – 31 , 33 ], metabolic genes were collected using BLAST [ 66 ] searches, and targeted searches for EC numbers [ 39 ] and keywords. For the reconstruction of the pathway map, we analysed all collected metabolic genes for the presence of signal peptides using SignalP [ 67 ], selecting only proteins that are predicted to be cytosolic, endoplasmic reticulum (ER) or Golgi enzymes and lack any conserved plastid (ASAF) or mitochondrial targeting sequences.…”

Ultrastructure and Membrane Traffic During Cell Division in the Marine Pennate Diatom Phaeodactylum tricornutum

“…In contrast to most other diatoms, P. tricornutum fusiform cells are only very poorly silicified ( Francius et al 2008 ). High concentrations of polysaccharides replace silica as a structural component of this novel cell wall ( Francius et al, 2008 , Tesson et al, 2009b , Willis et al, 2013 , Willis et al, 2014 ). This fact implies that P. tricornutum must rely much more on secretion of polysaccharides instead of a silicified frustule for formation of the cell wall.…”

Elevated pCO2 Level Affects the Extracellular Polymer Metabolism of Phaeodactylum tricornutum

“…Most genes encoding GTs were up-regulated, and increased expression of some ABC transporters indicate potentially increased activity in the Golgi apparatus leading to EPS secretion. These EPS then undergo further self-assembly in external environments and form cell frustule coatings, adhesive structures, or are used for motility (Wetherbee et al, 1998;Willis et al, 2015). The above two mechanistic responses were also observed as responses of F. cylindrus to extreme sea ice habitats (Aslam et al, 2018).…”