1887

Abstract

The internal hydrostatic pressure (turgor) of fungal cells is maintained at 400–500 kPa. The turgor is regulated by changes in ion flux and by production of the osmotically active metabolite glycerol. In , there are at least two genetically distinct pathways that function in adaptation to hyperosmotic shock. One involves a mitogen-activated protein (MAP) kinase cascade (kinases OS-4, OS-5 and OS-2 downstream of the osmosensing OS-1); the other is less understood, but involves the gene, which encodes a putative phosphatase. This study examined turgor regulation, electrical responses, ion fluxes and glycerol accumulation in the mutant. Turgor recovery after hyperosmotic treatment was similar to that in the wild-type, for both time-course (∼40 min) and magnitude. Prior to turgor recovery, the hyperosmotic shock caused a rapid transient depolarization of the membrane potential, followed by a sustained hyperpolarization that occurred concomitant with increased H efflux, indicating that the plasma membrane H-ATPase was being activated. These changes also occurred in the wild-type. Net fluxes of Ca and Cl during turgor recovery were similar to those in the wild-type, but K influx was attenuated in the mutant. The similar turgor recovery can be explained by the ion uptake, since glycerol did not accumulate in the mutant within the time frame of turgor recovery (but did accumulate in the wild-type). The results suggest that turgor regulation involves multi-faceted coordination of both ion flux and glycerol accumulation. Ion uptake is activated by a MAP kinase cascade, while CUT is required for glycerol accumulation.

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2007-05-01
2020-10-27
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