Apical cells of brown algae with particular reference to Sphacelariales, Dictyotales and Fucales

Abstract

SUMMARY Brown algae show a significant diversity in thallus forms, giving a great number of model systems for the study of many important morphogenetic mechanisms. Thallus growth in brown algae is diffuse, intercalary or apical. The latter takes place by means of one or more apical cells. Among the brown algal groups, Sphacelariales, Dictyotales and Fucales give the best examples of apical growth, and have been repeatedly used for the study of the morphogenetic role of apical cells. In Sphacelariales the apical cells appear strongly polarized, the polarity expressed also on the organization of the microtubule cytoskeleton. These cells show a type of growth that can be compared with tip growth of root hairs, moss protonemata, pollen tubes and fungal hyphae, and is called ‘tip‐like growth’. The thallus of Dictyotales grows by the activity of one or more apical cells showing variable degree of polarity. These cells do not exhibit any type of apical growth. In Fucales the vegetative thallus develops by means of an active apical meristem, which includes a large apical cell. This cell does not show polar organization or apical growth. However, in germinating zygotes of Fucales a polar axis is established and during the first stages of development they show a typical tip growth. In the present paper, the available information on the structure and division pattern of apical cells is presented. Their morphogenetic role is discussed, in relation to polarity, cytoskeleton organization, and apical dominance.

Intracellular eukaryotic pathogens in brown macroalgae in the Eastern Mediterranean, including LSU rRNA data for the oomycete Eurychasma dicksonii

“…Hakariya et al 2009, Muraosa et al 2009, Sekimoto et al 2009 Sparrow 1960). Members of the Sphacelariales show apical growth patterns (Katsaros 1995). These cells are strongly polarized, with a continuous flow of membrane material and polysaccharides to the tip of the cell (apical dome) resulting in cell wall expansion.…”

Fibonacci spirals in a brown alga [Sargassum muticum (Yendo) Fensholt] and in a land plant [Arabidopsis thaliana (L.) Heynh.]: a case of morphogenetic convergence

“…In (f) a longitudinal cut at a larger magnification and stained with calcofluor white shows its oblong section in this direction. described in the Sargassaceae [4,18,19,25,34,35]. It can be noted that the terminal cell of Sargassum is in some aspects similar to the apical cells observed in mosses as first emphasized by Church [4].…”

Cytoskeleton organisation during the infection of three brown algal species, Ectocarpus siliculosus,Ectocarpus crouaniorum and Pylaiella littoralis, by the intracellular marine oomycete Eurychasma dicksonii

“…The MT cytoskeleton organisation in the vegetative cells of E. siliculosus, E. crouaniorum and P. littoralis is similar to that already described in a variety of studies on different brown algal species (Katsaros et al . , ; Katsaros & Galatis ; Katsaros ). The MT organisation in a vegetative thallus cell of Ectocarpus siliculosus is presented in Fig.…”