A calcium homeostasis mechanism induced by heterologous expression of total RNA from chicory leaves in Xenopus oocytes.
Xenopus oocytes were injected with total RNA from chicory leaf tissues and then examined by the voltage-clamp technique. A double-step voltage protocol was used, with an initial hyperpolarization step from the holding potential of -35 to -140 mV followed by a second depolarization step to +60 mV. Two different outward currents were observed, one noninactivating (Ini), and one inactivating (Ii). Only the noninactivating outward current (Ini) could be induced by depolarization from -35 to +60 mV. The mean amplitude of Ini was 2915 +/- 848 nA (n = 11). This current, carried by chloride ions, declined nearly to the baseline in 153 +/- 64 sec (n = 13), and was highly dependent on intracellular calcium. After the rundown of Ini, the same oocyte was depolarized from -140 to +60 mV. This protocol induced an inactivating outward current (Ii) with a mean amplitude of 4461 +/- 1605 nA (n = 13). Ii was also carried by chloride ions and dependent on extracellular calcium. Ii was strongly inhibited by 100 micron extracellular La3+. These two types of chloride currents were also observed after IP3 injection in control oocytes. Ini and Ii were not observed in noninjected oocytes or water-injected oocytes. We suggest that the expression of total chicory leaf tissue RNA in Xenopus oocytes reveals a calcium homeostasis mechanism responsible for calcium mobilization from internal stores and subsequent calcium entry.
Debarbieux
M
M
Laboratoire de Physiologie Cellulaire, SN3, Université des Sciences et Technologie de Lille, 59655 Villeneuve d'Ascq Cedex, France.
Ouadid-Ahidouch
H
H
Delpierre
N
N
Vasseur
J
J
Prevarskaya
N
N
D000818:Animals; D002118:Calcium / Q000502:physiology*; D018651:Cichorium intybus / Q000235:genetics*; D018118:Chloride Channels / Q000235:genetics; D004594:Electrophysiology; D015870:Gene Expression; D006706:Homeostasis; D009865:Oocytes; D018515:Plant Leaves / Q000235:genetics*; D012313:RNA / Q000235:genetics; D014981:Xenopus
D018118:Chloride Channels; D012313:RNA; D002118:Calcium