Annexin-Enriched Preparation Elevates [Ca2+]cyt in Arabidopsis Root Epidermal Protoplasts.
(A) Increase in [Ca2+]cyt. An annexin-enriched preparation added (arrow) to the extracellular membrane face of Arabidopsis root epidermal protoplasts (constitutively expressing aequorin) caused a touch-induced transient increase in [Ca2+]cyt followed by a more sustained, dose-dependent increase (top and middle panels). Preincubation with 0.1 mM GdCl3 abolished the response (bottom panel).
(B) Effect of channel blockers on the increase in [Ca2+]cyt. Mean ± se peak transient [Ca2+]cyt responses from 5 mg/L annexin preparation with 10 mM external Ca2+. Channel blockers were incorporated at 0.1 mM (n = 5).
(C) Dose dependency of mean ± se peak transient [Ca2+]cyt response and apparent steady state basal [Ca2+]cyt. Basal [Ca2+]cyt was determined 7 to 10 min after the end of the transient (n = 4).