Morphology and dynamics of mitochondria in Mougeotia sp.

Mougeotia sp. are widely distributed freshwater algae that have a characteristic chloroplast rotation response to incident light. The mechanics of the response have been elucidated, but no work regarding the bioenergetics of this process has been reported. The current study examined the morphology and movement dynamics of mitochondria in this alga. A novel method, utilizing DASPMI (dimethylaminostyrylmethylpyridiniumiodine) fluorescent dye, was developed to allow vital mitochondrial staining while avoiding sequestration of the dye by numerous cytoplasmic vesicles and then used to study mitochondrial dynamics. Mitochondria were elongated tubular structures that were significantly asymmetrically located in the perinuclear and chloroplast edge regions. The mitochondria displayed small amplitude undirected movements with occasional high-velocity bursts of directional movement which were of greater magnitude. These latter movements were inhibited by a 30-min incubation with latrunculin (50 µM), but were unaffected by incubation with colchicine (10 µM), indicating that the actin, but not the microtubule cytoskeleton, is involved. The method used and the findings reported will allow research to be undertaken on the contribution of the chondriome to the chloroplast rotation response and other aspects of the bioenergetics of this organism.