Figure 3.

Effects of increasing extracellular Ca²⁺ on GLR3.3-mediated responses to micromolar Glu. A, Increasing external Ca²⁺ from 1 mm to 10 mm increased the magnitude of the membrane depolarization induced by 25 μm Glu. Even at the higher Ca²⁺ concentration, glr3.3-1 root cells did not depolarize in response to this low level of Glu. The glr3.3-2 allele also failed to respond (data not shown). See the text for mean peak values. B, A rise in cytosolic Ca²⁺ in response to 25 μm Glu was detected in wild-type root cells bathed in 10 mm Ca²⁺ (n = 7) but not when external Ca²⁺ was 1 mm (n = 4). Even in the presence of 10 mm external Ca²⁺, glr3.3-1 mutants did not show a detectable response to 25 μm Glu (n = 6). C, A rise in cytosolic Ca²⁺ (assayed by aequorin luminescence) in response to shifts of external Ca²⁺ from 1 mm to 10 mm was greatly enhanced by pretreatment with 10 μm Glu. n = 8 for the 0 Glu trials and n = 13 for the 10 μm Glu trials.