Calcium and tip growth inNeurospora crassa |
| |
Authors: | L B Silverman-Gavrila R R Lew |
| |
Institution: | (1) Biology Department, York University, 4700 Keele Street, M3J 1P3 Toronto, ON, Canada |
| |
Abstract: | Summary We examined the ionic regulation of tip growth inNeurospora crassa by a combination of electrophysiology and confocal microscopy. To determine if transmembrane ionic fluxes are required for tip growth, we voltage clamped the membrane from –200 to +50 mV. In this voltage range, transmembrane ionic fluxes would either reverse (e.g., K+) or change dramatically (e.g., Ca2+ influx) but had no effect on hyphal growth rates. Therefore, ionic fluxes (including Ca2+ influx) may not be required for tip growth. However, intracellular Ca2+ may still play an obligatory role in tip growth. To assess this possibility, we first increased cytosolic Ca2+ directly by ionophoresis. Elevated Ca2+ induced subapical branch initiation, often multiple tips. At hyphal tips, fluorescence ratio imaging using fluo-3 and fura-red revealed a pronounced tip-high Ca2+ gradient within 10 m of the tip in growing hyphae which was not observed in nongrowing hyphae. Injection of the Ca2+ chelator 1,2-bis(ortho-aminophenoxy)ethane-N,N,N ,N -tetrapotassium acetate consistently inhibited growth concomitantly with a depletion of intracellular Ca2+ and dissipation of the tip-high gradient. We conclude that Ca2+ plays a regulatory role in tip initiation and the maintenance of tip growth. Because plasma membrane ionic fluxes do not play a role in tip growth, we suggest that the tip-high Ca2+ gradient is generated from intracellular Ca2+ stores in the ascomyceteN. crassa.Abbreviations BAPTA
1,2-bis(ortho-aminophenoxy)ethane-N,N,N ,N -tetrapotassium acetate
- Ca2+]i
intracellular Ca2+ concentration
- fluo-3
2,7-dichloro-6-hydroxy-3-oxo-9-xanthenyl-4 -methyl-2,2 -(ethylenedioxy)dianiline-N,N,N ,N -tetraacetic acid |
| |
Keywords: | Calcium gradient Tip growth Ratio fluorescence imaging Ca2+ chelator Voltage clamping Neurospora crassa |
本文献已被 SpringerLink 等数据库收录! |
|