Transport of Small Ions and Molecules through the Plasma Membrane of Filamentous Fungi

Abstract

Less than 1% of the estimated number of fungal species have been investigated concerning the transport of low-molecular-weight nutrients and metabolites through the plasma membrane. This is surprising if one considers the importance of the processes at the plasma membrane for the cell: this membrane mediates between the cell and its environment. Concentrating on filamentous fungi, in this review emphasis is placed on relating results from biophysical chemistry, membrane transport, fungal physiology, and fungal ecology. Among the treated subjects are the consequences of the small dimension of hyphae, the habitat and membrane transport, the properties of the plasma membrane, the efflux of metabolites, and the regulation of membrane transport. Special attention is given to methodological problems occurring with filamentous fungi. A great part of the presented material relies on work with Neurospora crassa, because for this fungus the most complete picture of plasma membrane transport exists. Following the conviction that we need "concepts instead of experiments", we delineate the lively network of membrane transport systems rather than listing the properties of single transport systems.

Physiological and Transcriptional Responses to High Concentrations of Lactic Acid in Anaerobic Chemostat Cultures of Saccharomyces cerevisiae

“…Originally, TPO2 and TPO3 were thought to be polyamine transporters localized to the vacuole (57); however, there is evidence for plasma membrane localization (4), and deletion of TPO2 has been correlated to increased accumulation of intracellular acetate (16). Involvement of Tpo2p and/or Tpo3p in lactate/proton antiporter activity, combined with proton expulsion via the plasma membrane ATPase, which has an ATP/proton stoichiometry of 1 (7,53), would be consistent with a zero net ATP yield for lactate fermentation (60). However, since even a double deletion of TPO2 and TPO3 did not result in impaired growth in the presence of lactic acid, either the encoded transporters are not involved in lactate tolerance or redundant exporters are encoded by the S. cerevisiae genome.…”

Nutrient transport into germinating Trichoderma atroviride conidia and development of its driving force

“…Second, it is feasible that germinating conidia produce organic acids, which could be transported by anion-proton symport, driven by glycolysis and the TCA cycle, major producers of cytoplasmic H + . Such a transport system has been considered in red blood cells and in Ehrlich ascites cells (Johnson et al, 1980), in bacteria (reviewed by Konings et al, 1992) and in fungi, which are known to be powerful producers of organic acids (reviewed by Konings et al, 1992;Burgstaller, 1997Burgstaller, , 2006. Support for this explanation of the uncoupler sensitivity should be obtained by future direct measurements of membrane potential, fluxes of organic acids, and Na + and H + .…”

Biotrophy and rust haustoria

“…In Neurospora crassa, one of the best studied species, facilitators and secondary transporters have been found with speci®cities for amino acids, hexoses and ions [5,26]. Studies with symbionts, such as mycorrhizal fungi or obligately biotrophic parasites, have been hampered by the close association of fungus and plant.…”