Behavior of mitochondria, microtubules, and actin in the triangular yeastTrigonopsis variabilis

Abstract

Summary. Dimorphic yeast Trigonopsis variabilis is a uniquespecies that can form either an ellipsoidal or a triangular cell depending upon nutritional conditions. This fluorescence microscopic study was intended to correlate morphological changes of mitochondria in the triangular cells with the distribution of the cytoskeleton. In addition, unique features in the behavior of the cytoskeleton were also examined during triangular cell formation. In log-phase cells stained with 4',6-diamidino-2-phenylindole, mitochondrial nucleoids appeared as a string of beads throughout the vegetative growth. The profile of mitochondria stained by 3,3'-dihexyloxacarbocyanine iodide showed a network corresponding to the fluorescence images of mitochondrial nucleoids in both mother and daughter cells. Cellcycle-dependent fragmentation of mitochondria was not discerned. As the culture reached stationary phase, a network of mitochondria gradually changed to form unique rings that were located new the angles of triangular cells. When examined by immunofluorescence microscopy with anti-tubulin antibody, microtubules were found to be well developed along the sides of ceils in the cytoplasm of T. variabilis interphase cells. Although distributions of microtubules and mitochondria are different during cell cycle as a whole, cytoplasmic microtubules frequently extended along a part of the mitochondria in budded cells, suggesting correlation of microtubules and mitochondria. Rhodamine-phalloidin staining revealed both actin patches and cables. Actin cables elongated from mother cells into the buds and showed close proximity to mitochondria, although complete overlapping of both structures was rare. Moreover, actin patches localized on the mitochondrial network at a frequency of 65%. These results suggested that actin cables and patches, as well as microtubules, participated in the distribution of mitochondria. The localization of actin patches separated towards opposite ends at a bud tip when the bud grew to medium size. The unique localization of actin patches is responsible for bi-directional growth of the bud, forming triangular cells.

Aldehyde dehydrogenase, Ald4p, is a major component of mitochondrial fluorescent inclusion bodies in the yeast Saccharomyces cerevisiae

“…Migration of tubular mitochondria into the bud cells has also been clearly shown in the triangular yeast Trigonopsis variabilis by vital staining with DiOC 6 (3) (Miyakawa and Yanagamizu, 1998). Similarly, formation of a tubular network of fused mitochondrion has been shown by DiOC 6 (3) staining of Saccharomycodes ludwigii during meiosis and sporulation (Miyakawa et al, 2012).…”

“…Mitochondria also have a highly tubular structure in growing cells at log-phase, and they migrate into the buds with one end of the tubular mitochondria leading the way, as shown by DAPI and DiOC 6 (3) staining or by labeling of mitochondria with GFP ( Miyakawa et al, 2010 ). Migration of tubular mitochondria into the bud cells has also been clearly shown in the triangular yeast Trigonopsis variabilis by vital staining with DiOC 6 (3) ( Miyakawa and Yanagamizu, 1998 ). Similarly, formation of a tubular network of fused mitochondrion has been shown by DiOC 6 (3) staining of Saccharomycodes ludwigii during meiosis and sporulation ( Miyakawa et al, 2012 ).…”

Morphology of mitochondrial nucleoids, mitochondria, and nuclei during meiosis and sporulation of the yeast Saccharomycodes ludwigii

“…Stock solution of DiOC 6 (3) (10 μg/ml) was added at a fi nal concentration of 1 μg/ml and incubated for 5 min at 30 C. Mitochondria were observed under B excitation. Double staining with DAPI and DiOC 6 (3) was carried out as follows: To sporulating cells suspended in NS buffer were added DiOC 6 (3) and DAPI, each at a fi nal concentration of 1 μg/ml, which were left for 5 min at 30 C. Mitochondrial nucleoids and nuclei were observed under UV excitation and mitochondria were observed under B excitation (Miyakawa and Yanagamizu, 1998;Miyakawa et al, 1994).…”

Organization and dynamics of yeast mitochondrial nucleoids

“…In the unique triangular yeast, Trigonopsis variabilis , tubular mitochondria also highly developed and transmitted to the bud. 93 ) The budding yeast Saccharomycodes ludwigii and Yarrowia lipolytica also have tubular mitochondria. 94 , 95 ) It may be possible that mitochondrial distribution is regulated in either actin-dependent or tubulin-dependent manners in each yeast species.…”