High molecular mass glycoproteins associated with the siliceous scales and bristles of Mallomonas splendens (Synurophyceae) may be involved in cell surface development and maintenance

Abstract

Abstract.The elaborate scale case of Mallomonas splendens (Synurophyceae) consists of an overlapping arrangement of siliceous scales. In addition, siliceous bristles are attached to specialized base plate scales located at both the anterior and posterior ends of the cells. We have generated monoclonal antibodies against molecules associated with the scale case of M. splendens. One of these antibodies, designated MsS.H9, labelled a proteinaceous epitope of high-molecular-mass cell surface glycoproteins. Immunofluorescence and immunoelectron microscopy demonstrated that only two regions of M. splendens scale cases were labelled by MsS.H9, namely, the upper surface of the scales that contact neighboring scales and the bases of the bristles. Immunoelectron microscopy using thin sections of M. splendens cells showed these labelling sites corresponded to the amorphous material at the sites of scale-to-scale overlap and to a fibrillar complex located at scale-to-bristle attachment sites. Scales and bristles of M. splendens are formed within the cell, in silica deposition vesicles, lmmunolabelling of cell sections containing developing scales and bristles showed that MsS.H9 labelling sites were present very early in the formation of these cell surface components. MsS.H9 labelling was also found associated with developing flagellar hairs whereas no labelling was detected on these structures after their deployment onto the flagellum. The location of MsS.H9 labelling sites strongly suggests that the molecule(s) recognized by the antibody plays a role in the adhesion of the individual components making up the scale case of M. splendens.

Substratum adhesion and gliding in a diatom are mediated by extracellular proteoglycans

“…For motility studies, cells were settled onto slides and microspheres added (silica, 0.6 lm diameter; Bangs Laboratories Inc., Carmel, Ind., USA). Cells were viewed and recorded as described by Ludwig et al (1996).…”

“…The FACs were either dissolved directly in SDS-sample buer (Laemmli 1970; one volume frustules in three volumes buer) or lyophilised FACs were dissolved in SDS-sample buer. Samples for non-reducing SDS-PAGE were prepared without reducing agent in sample buer; SDS-PAGE, gel staining, electroblotting and blot staining were as described in Ludwig et al (1996). Monoclonal antibody binding was detected with anti-mouse IgG or anti-mouse IgM coupled to horseradish peroxidase (Sigma).…”

Competition between Silicifiers and Non-silicifiers in the Past and Present Ocean and Its Evolutionary Impacts

“…Repeatedly we can observe the evolution of similar morphologies in distantly related taxa, such as micropores in the siliceous components of choanoflagellates (Leadbeater, 2015), chrysophytes (Sandgren et al, 1996), diatoms (Finkel and Kotrc, 2010), and haptophytes (Yoshida et al, 2006); spines and spicules in radiolarians (Kunitomo et al, 2006), dictyochophytes (Preisig, 1994), centrohelids (Zlatogursky, 2016), and sponges (Weaver et al, 2007); or tablets and scales in haptophytes (Yoshida et al, 2006), rhizarians (Nomura and Ishida, 2016), synurophytes (Sandgren et al, 1996), amoebozoans (Lahr et al, 2013), and brachiopods (Williams et al, 2001). Though the genes governing the production of these silica patterns are not fully understood, many parallels with the molecular biology of diatom silicification are emerging, such as a role for glycoproteins in choanoflagellates (Gong et al, 2010) and synurophytes (Ludwig et al, 1996), cytoskeleton-mediated shaping of the growing silica structure in multiple taxa (Leadbeater, 2015;Nomura and Ishida, 2016) and the presence of post-translationally modified LCPAs in haptophyte (Durak et al, 2016) and sponge (Matsunaga et al, 2007) silica. These polymerization mechanisms have apparently evolved independently from those in diatoms, suggesting repeated recruitment of similar molecules for silica formation and patterning, and therefore a similar role for silicification-related evolutionary competition and speciation as diatoms.…”

A sustained passion for intracellular trafficking

“…I became fascinated by the elegant beauty of the single-celled algae that were the focus of study in Rick Wetherbee's lab in the Botany School. I worked with a postdoctoral fellow, Jan Lind, to characterize the extracellular glycoproteins these organisms use as cellular glues (Ludwig et al ., 1996). I continued this work as an “honours” student, which in the Australian system is an optional fourth year of university that allows a full year of dedicated bench research.…”