Development and function of plasmodesmata in zygotes of Fucus distichus

Abstract

Brown algae have plasmodesmata, tiny tubular cytoplasmic channels connecting adjacent cells. The lumen of plasmodesmata is 10-20 nm wide, and it takes a simple form, without a desmotubule (the inner membrane structure consisting of endoplasmic reticulum in the plasmodesmata of green plants). In this study, we analyzed the ultrastructure and distribution of plasmodesmata during development of Fucus distichus zygotes. The first cytokinesis of zygotes in brown algae is not accompanied by plasmodesmata formation. As the germlings develop, plasmodesmata are found in all septal cell walls, including the first cell division plane. Plasmodesmata are formed de novo on the existing cell wall. Pit fields, which are clusters of plasmodesmata, were observed in germlings with differentiated cell layers. Apart from the normal plasmodesmata, these pit fields had branched plasmodesmata that appeared to arise from the lateral preexisting ones. Fluorescent tracers with different molecular sizes were microinjected to examine the size exclusion limit of molecules for transit through the plasmodesmata. Fluorescein isothiocyanate (FITC)-dextran of 3 kDa size was spread over the germlings, and 10 kDa FITC-dextran was tracked only in the rhizoid. The size exclusion limit was < 10 kDa for the thallus but < 40 kDa for the rhizoid.

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

“…) and the other on Fucus distichus (Nagasato et al. ) germlings. In 3‐, 8‐, and 12‐celled F. spiralis germlings, 10 kDa fluorescein isothiocyanate (FITC)‐conjugated dextran (FD) was dispersed throughout all cells of the germlings.…”

“…, Nagasato et al. ). Although symplastic transport has been studied using radioisotopes (Schmitz and Lobban , Amat and Srivastava ), it has not elucidated the translocation capacity of plasmodesmata in brown algae.…”

“…The adult sporophytes of the Fucales show complex multicellular thalli, and their plasmodesmata form clusters known as “pit fields.” In young sporophytes, plasmodesmata are separately arranged over the walls until the cellular differentiation stage (Nagasato et al. ). In 10‐d‐old F. distichus sporophytes, pit fields were observed only in the thallus region.…”

A review of reproduction in the seaweed genus Fucus (Ochrophyta, Fucales): Background for renewed consideration as a model organism

“…(Manton & Clarke, 1950). For further microscopic descriptions of gamete structure and fertilization in Fucus, see : Pollock, 1970;Brawley et al, 1976;Callow et al, 1978;Motomura, 1994. Recent advances in electron microscopy (high pressure freezing, microinjection of fluorescent dyes) examining ultrastructure, distribution, and de novo formation of plasmodesmata in F. distichus promise to advance studies of receptors and cell-to-cell communication (Nagasato et al, 2015).…”

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).…”