In:
Functional Plant Biology, CSIRO Publishing, Vol. 28, No. 2 ( 2001), p. 87-
Abstract:
Membrane transport activity associated with growth and nutritional status of a
marine microheterotroph Thraustochytrium sp. was studied using non-invasive ion-selective slowly vibrating microelectrodes (the MIFE
technique). Net fluxes of H + , Ca 2+ and Na + underwent
regular changes as the cell progressed from the zoospore to sporangium stages of development. The most pronounced change was a decrease in the net H
+ influx, which we suggest could be associated with the changes in cytoskeletal organization required for cell cleavage and
zoospore release. As cell development progressed from the zoospore stage towards maturity, non-damping endogenous ultradian oscillations (period range
of several minutes) became evident. At the sporangium stage, as many as 85% of cells possessed oscillatory membrane transport activity. It is
suggested that ultradian ion flux oscillations in Thraustochytrium sp. may be causally linked with cell
developmental processes. Discrete Fourier transform and cross-correlation analysis revealed a close association between oscillatory patterns of H
+ and Na + fluxes. The possibility that these oscillations result from the rhythmical activity of a
Na + /H + co-transporter located at the plasma membrane of
Thraustochytrium sp. is considered. Oscillations in net Ca 2+ flux were apparently not linked to those in
H+ and Na + , and are believed to be due to some other physiological processes. Periods of net H
+ and Na + flux oscillations were strongly dependent on the external Na
+ concentrations in the bathing medium. As sodiu m
is considered to be an essential element in Thraustochytrium sp., it is suggested that the
functional role of such ultradian oscillations may be their involvement in the frequency-encoding mechanism that provides developing cells with information
about environment, and nutritional status in particular.
Type of Medium:
Online Resource
ISSN:
1445-4408
Language:
English
Publisher:
CSIRO Publishing
Publication Date:
2001
SSG:
12
