Various ion channels in leaf protoplasts from the moss Physcomitrella patens

Many molecular and genetic tools are available for the moss Physcomitrella patens and make this anatomically simple plant an attractive model system. Here, the ionic conductances in the plasma membrane of protoplasts derived from the gametophytic leaves of P. patens were studied using the patch clamp technique. Though the leaves contain only a single layer of uniform appearing cells, the results show some diversity in the current types among protoplasts. In whole cell preparations, both outwardly and inwardly rectifying potassium currents were observed. The currents were time- and voltage-dependent and resemble the currents found in higher plants that are mediated by potassium channels. Current-voltage plots of the tail currents indicate that the currents were mainly carried by K+. The inward potassium channels were highly permeable to ammonium, but not sodium. In standard conditions, using potassium, calcium and chloride as major ions, some cells displayed only outwardly rectifying potassium currents. In addition, time-independent and novel deactivating cation currents were observed in another set of cells. In summary, moss protoplasts display diverse current types, many of which are also observed to be typical in higher plant species. (C) 2003 Elsevier Science Ireland Ltd. All rights reserved.