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The dynamic behavior of cytoplasmic F-actin in growing hyphae (1993)

Jackson, S. L. ; Heath, I. B.

Springer

Protoplasma 173 (1993), S. 23-34

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ISSN: 1615-6102

Keywords: Tip growth ; Actin ; Rhodamine phalloidin ; Electroporation

Source: Springer Online Journal Archives 1860-2000

Topics: Biology

Notes: Summary A dynamic population of cytoplasmic F-actin was observed with electroporated rhodamine phalloidin (RP) staining in growing hyphae ofSaprolegnia ferax. This central actin population was distinct from the fibrillar peripheral network previously described in chemically fixed hyphae in that it was diffuse, pervaded the entire cytoplasm and was most concentrated in the central cytoplasm 8.4 μm from the tip. The peripheral network did not stain with electroporated RP. The apical concentration of central cytoplasmic actin was only present in growing hyphae and developed prior to tip extension. It co-localized with the polarized distribution of mitochondria and endoplasmic reticulum in the tip, suggesting that it functions in positioning these organelles during tip growth. Within the central actin there was a consistent apical cleft which only occurred in growing hyphae and whose position predicted the direction of tip growth. This cleft was coincident with the known accumulation of apical wall vesicles, suggesting that it is either established by vesicle exclusion of the central actin network or is permeated by a portion of the in vivo unstained peripheral network. Photobleaching studies showed that in both growing and non-growing hyphae, cytoplasmic actin continually and rapidly moved from subapical regions to the tip where it accumulated. It mostly moved forward at the rate of tip growth, while some also left the tip, presumably to populate subapical regions.

Type of Medium: Electronic Resource

URL: http://dx.doi.org/10.1007/BF01378859

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Polarized cytoplasmic movement and inhibition of saltations induced by calcium-mediated effects of microbeams in fungal hyphae (1986)

McKerracher, L. J. ; Heath, I. B.

New York, NY : Wiley-Blackwell

Cell Motility and the Cytoskeleton 6 (1986), S. 136-145

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ISSN: 0886-1544

Keywords: cytoplasmic movement ; microbeam ; Ca++ ; fungi ; saltatory movement ; cytoskeleton ; Life and Medical Sciences ; Cell & Developmental Biology

Source: Wiley InterScience Backfile Collection 1832-2000

Topics: Biology , Medicine

Notes: We have investigated the mechanisms that hyphae of the fungus Basidiobolus magnus use to accomplish bulk movement of their cytoplasm and saltatory organelle movements. When cells were irradiated with an ultraviolet microbeam, cytoplasmic contraction occurred. The posterior cytoplasm (toward the septum) always moved forward toward the irradiated area, whereas anterior cytoplasm (between the cell tip and target) never contracted back toward the site of irradiation. Thus, there is an intrinsic polarity in the cytoplasm. Irradiations also arrested saltatory movements. The effects of irradiation on both saltations and cytoplasmic movement appear to be mediated by Ca++. Chelating exogenous Ca++ before irradiation eliminated contractions and prevented the inhibition of saltations. Furthermore, the effects of irradiation could be duplicated by using the Ca++ ionophore A23187. We relate the present results to our previous report on the effects of irradiation on the cytoskeleton [McKerracher and Heath, 1986]. We conclude that two separate cytoskeletal networks exist in fungal cells, and that an actin-containing network generates bulk cytoplasmic movement.

Additional Material: 9 Ill.