Abstract Detail

Cell biology

Halat, Laryssa [1], Galway, Moira [1], Garbary, David [1].

Synchronized separation and shedding of outer cell wall layers in response to epiphyte accumulation in the brown alga Ascophyllum nodosum.

Rockweed (Ascophyllum nodosum) is a perennial, long-lived, multicellular brown alga that is a dominant species along the rocky shores of Atlantic Canada. A process of intermittent epidermal shedding removes colonizing epiphytes. This involves the detachment of thin sheets of material from centimeter-scale areas of epidermis. Based on previous observations, and on reports of similar processes in other seaweeds, it was hypothesized that this synchronized, patchy shedding could involve separation of apical portions of epidermal cells following asymmetrical cytokinesis, or it could involve abscission-like separation of the outer cell walls of the epidermal cells. The two models were evaluated by examining epidermal shedding using a variety of different histochemical and microscopical approaches. Epiphyte accumulation on epidermal cells is accompanied by the formation of thick, multilayered outer cell walls. These walls initially stained uniformly with a fluorescent dye for cell wall carbohydrates. Approaching shedding, however, the walls developed unstained central regions, which under certain conditions stained with a fluorescent lipophilic dye. These regions were also differentially stained by toluidine blue. In transmission electron microscopy thin sections, the central regions appeared amorphous, in contrast to the surrounding fibrillar cell walls. Cell wall separation occurred in the central regions, and extended to the upper portion of the side walls between adjoining epidermal cells, so that the shed layer consisted of an interconnected series of shallow dome-like structures. Light microscopy and scanning electron microscopy (both conventional, using fixed tissue, and environmental, using fresh tissue) revealed that initially, long and apparently elastic fibrils extended between separating cell wall layers and the underlying epidermis. Both cell wall composition and the factors that regulate this synchronized process of cell wall separation warrant further investigation.

1 - St. Francis Xavier University, Department of Biology, 1 West St., Antigonish, NS, B2G 2W5, Canada

Keywords:
abscission
Ascophyllum nodosum
Cell wall
epidermis
Epiphyte
Phaeophyceae.

Presentation Type: Poster:Posters for Topics
Session: P
Location: Hall D/The Shaw Conference Centre
Date: Monday, July 27th, 2015
Time: 5:30 PM
Number: PCL012
Abstract ID:1226
Candidate for Awards:None