Mitochondrial Dynamics in Red Algae. 3. Filament Apices in Colaconema caespitosum (Acrochaetiales) and Antithamnion cruciatum (Ceramiales)

doi:2006.21.3.323

Algae > Volume 21(3); 2006 > Article

Algae 2006;21(3): 323-332. doi: https://doi.org/10.4490/algae.2006.21.3.323

David J. Garbary^* and Pei Zuchang

Department of Biology, St. Francis Xavier University, Antigonish, Nova Scotia, Canada B2G 1C0

ABSTRACT

Mitochondrial distribution and abundance were assessed during the growth of apical and subapical cells in the red algae Colaconema caespitosum (J. Agardh) Jackelman, Stegenga and Bolton and Antithamnion cruciatum (C. Agardh) Nageli after staining with 3,3’-dihexyloxacarbocyanine iodide [DiOC6(3)] and 2,4’-dimethylaminostyryl-Nethylpyridinium iodide (DASPEI). In fully elongate apical cells of C. caespitosum there were 100-120 mitochondria. During apical cell enlargement and division there is a doubling and then halving of the mitochondrial numbers. Apical cells prior to cytokinesis in young filaments are smaller than in mature filaments (ca. 50 and 100 μm long, respectively) and have fewer mitochondria (ca. 100 and 120 mitochondria per cell, respectively). In older vegetative cells mitochondria tend to aggregate at opposite ends of the cells with some mitochondria associated with the central nucleus or at points of apparent branch initiation. There is a greater density of mitochondria in apical cells of smaller versus larger plants (one mitochondrion per 6.3 μm3 and 9.8 μm3, respectively), suggesting that apical cells of younger plants may be more metabolically active. Male and female gametophytic thalli of Antithamnion cruciatum had similar numbers of mitochondria in apical cells of indeterminate axes, as did gametophytic and sporophytic thalli. There were about 40-50 mitochondria in fully elongated apical cells with about half this number in newly divided apical and subapical cells. Apical cells of determinate branches had more mitochondria (60-77) than indeterminate branches (60-70 vs. 40-50). In both species and in all cell types mitochondrial numbers were highly correlated with cell size.

Key words: Acrochaetiaceae, Antithamnion, apical cells, Colaconema, DiOC6(3), DASPEI, cell elongation, DAPI, mitochondria,