The roles of Ca2+ and plasma membrane ion channels in hyphal tip growth of Neurospora crassa (original) (raw)

1995, Journal of cell science

Growing hyphae of the ascomycete fungus Neurospora crassa contained a tip-high gradient of cytoplasmic Ca2+, which was absent in non-growing hyphae and was insensitive to Gd3+ in the medium. Patch clamp recordings in the cell-attached mode, from the plasma membrane of these hyphae, showed two types of channel activities; spontaneous and stretch activated. The spontaneous channels were identified as inward K+ channels based on inhibition by tetraethylammonium. The stretch activated channels had increased amplitudes in response to elevated Ca2+ in the pipette solution, and thus are permeable to Ca2+ and mediate inward Ca2+ movement. Gd3+, which is an inhibitor of some stretch activated channels, incompletely inhibited stretch activated channel activity. Both tetraethylammonium and Gd3+ only transiently reduced the rates of tip growth without changing tip morphology, thus indicating that the channels are not absolutely essential for tip growth. Furthermore, in contrast to the hyphae of...