Intercellular translocation of molecules via plasmodesmata in the multiseriate filamentous brown alga, Halopteris congesta (Sphacelariales, Phaeophyceae)

Abstract

Despite the high number of studies on the fine structure of brown algal cells, only limited information is available on the intercelluar transportation of molecules via plasmodesmata in brown algae. In this study, plasmodesmatal permeability of Halopteris congesta was examined by observing the translocation of microinjected fluorescent tracers of different molecular sizes. The tip region of H. congesta consists of a cylindrical apical cell, while the basal region is multiseriate. Fluorescein isothiocyanate-dextran (FD; 3, 10, and 20 kDa) and recombinant green fluorescent protein (27 kDa) were injected into the apical cell and were observed to diffuse into the neighboring cells. FD of 40 kDa was detected only in the injected apical cell. The plasmodesmatal size exclusion limit was considered to be more than 20 kDa and less than 40 kDa. The extent of translocation of 3 and 10 kDa FD from the apical to neighboring cells 2 h postinjection was estimated based on the fluorescence intensity. It was suggested that the diffusing capacity of plasmodesmata varied according to molecular size. In order to examine acropetal and/or basipetal direction of molecular movement, 3 and 10 kDa FD were injected into the third cell from the apical cell. Successive observations indicated that the diffusion of fluorescence in the acropetal direction took longer than that in the basipetal direction. No ultrastructural difference in plasmodesmata was noted among the cross walls.

Simultaneous visualization of the actin plate and new cell partition membrane during cytokinesis in the brown algaSphacelaria rigidula(Sphacelariales, Phaeophyceae)

“…6g-j), as in other brown algae observed by rapid freezing and freeze-substitution (Fig. 6a-e) (Nagasato & Motomura 2002a;Katsaros et al 2009;Nagasato et al 2010;Terauchi et al 2012;Nagasato et al 2017).…”

“…3e,f). These channels correspond to the preplasmodesmata (Terauchi et al 2012;Nagasato et al 2017). In contrast to untreated cells (Fig.…”

“…In brown algae, it is difficult to observe well-preserved membrane structures using chemical fixation for TEM (Nagasato et al 2018) and thus to interpret the obtained images. In this context, applying rapid freezing and freeze-substitution for ultrastructural observations of cytokinesis in brown algae provides new information (Nagasato & Motomura 2002a;Katsaros et al 2009;Nagasato et al 2010;Terauchi et al 2012;Nagasato et al 2017). Studies using these techniques revealed that cytokinesis proceeds by the outgrowth of the new cell partition membrane in many brown algae, but not Sphacelaria rigidula.…”

“…Studies using these techniques revealed that cytokinesis proceeds by the outgrowth of the new cell partition membrane in many brown algae, but not Sphacelaria rigidula. In the zygotes of Scytosiphon lomentaria (Nagasato & Motomura 2002a) and Silvetia babingtonii (Nagasato et al 2010) and the apical meristem of Dictyota dichotoma (Terauchi et al 2012) and Halopteris congesta (Nagasato et al 2017), cytokinesis begins with the aggregation and fusion of Golgi vesicles and flat cisternae on the cytokinetic plane to form the new cell partition membrane. In contrast, furrows of the plasma membrane occur in the future cytokinetic plane of the apical cells of S. rigidula (Katsaros et al 2009).…”

Targeted CRISPR‐Cas9‐based gene knockouts in the model brown alga Ectocarpus

“…Two or three drops of half-strength PES medium were then added. The microinjection apparatus has been described previously (Nagasato et al, 2015(Nagasato et al, , 2017. Micromanipulators consisting of a coarse manipulator (MN-4; Narishige Co. Ltd, Tokyo, Japan) and a three-axis joystick oil hydraulic micromanipulator (MO-202; Narishige) were coupled to an Olympus IX71 inverted microscope (Olympus, Tokyo, Japan).…”