Changes in Cell Wall Structure During Rhizoid Formation of Silvetia babingtonii (Fucales, Phaeophyceae) Zygotes

Abstract

We examined the ultrastructure of the cell wall and immunolocalization of alginates using specific antibodies against M‐rich alginates and MG blocks during rhizoid formation in fucoid zygotes, Silvetia babingtonii. The thallus region of 24‐h‐old zygotes had a cell wall made of three layers with different fiber distribution. In the 12‐h‐old zygotes, three layers in the thallus were observed before rhizoid formation, namely the inner, middle, and outer layers. During rhizoid elongation, only the inner layer was apparent close to the rhizoid tip area. Immunoelectron microscopy detected M‐rich blocks of alginate on the inner half of the cell wall, irrespective of the number of layers in the thallus and rhizoid regions. The MG blocks were seen to cover a slightly wider area than M‐rich alginate blocks. It was suggested that parts of M in mannuronan would be rapidly converted to G, and MG‐blocks are generated. Transcriptome analysis was performed using 3 ‐, 10 ‐, and 24‐h‐old zygotes after fertilization to examine the relationship between gene expression and alginate synthesis over time. The expression of two mannuronan C5‐epimerase homologs that convert mannuronic acid into guluronic acid in alginates was upregulated or downregulated over the course of the examination.

The longitudinal growth of the embryo of the kelpSaccharinadepends on actin filaments that control the formation of an alginate corset in the cell wall

“…1P). Therefore, M-M rich alginates appear to be present in the most recent cell wall layers, which is in agreement with reports in Fucus embryos (Yonamine et al, 2021).…”

Microbe-assisted seedling crop improvement by a seaweed extract to address fucalean forest restoration

“…Although the synthetic pathways of alginates are not fully understood, it is thought that alginates are first synthesized as a polymer of mannuronic acid (a component of alginic acid) by alginate synthase and that some of the mannuronic acid is converted to guluronic acid (Michel et al, 2010). Alginates can influence the mechanical properties of cell walls in the rhizoids of developing zygotes of Fucales (Linardic, 2018;Yonamine et al, 2021) and provide for a stronger rhizoid system. We can assume that the A2 seedlings had stronger rhizoids that allowed them to adhere more firmly to the tiles.…”