Low temperature effects on growth and actin cytoskeleton organisation in suspension cells of winter oilseed rape
2001
Egierszdorff, S. | Kacperska, A.
Rhodamine-phalloidin staining of winter oilseed rape suspension cells revealed that the structure of actin cytoskeleton changes with the phase of cell growth. In small, 4-day-old cells, entering the exponential phase of growth, a dense and uniformly distributed cortical microfilament networks was seen. In six-day-old vacuolated cells, which reached the stationary phase of growth, the actin cytoskeleton was composed of thicker microfilament cables in irregular arrangements. In cells acclimated in cold for 7 days a dense, uniformly distributed and cortical microfilament network was still seen. The fine microfilament network was sensitive to extracellular freezing since the structures underwent depolymerization at -3 degrees C (in the presence of extracellular ice), both in non-acclimated and cold-acclimated cells. The thicker transvacuolar cables in cells of the stationary growth phase resisted freezing to -7 degrees C. Acclimation of suspensions at 2 degrees C resulted in slowing down growth of cells and in the increased freezing tolerance of cells as indicated by a decrease of LT50 from -11 degrees C to -17.5 degrees or to -25 degrees C when determined 7 or 20 days after the beginning of the cold treatment, respectively. Freezing tolerance of non-acclimated cells decreased from -11 degrees C to -8 degrees C during subculture, showing a transient increase to -17 degrees C on the day 6. Results indicate that the arrangement of actin microfilaments and their sensitivity to freezing-induced depolymerization depends on the phase of cell growth rather than on cell acclimation status. Possible mechanisms involved in the freezing-induced depolymerization of actin microfilaments are discussed.
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