The gene encoding voltage-gated channel with high affinity for Ca2+ permeat
ion has not been cloned from plants. In the present study, we isolated a fu
ll-length cDNA encoding a putative Ca2+ channel (AtTPC1) from Arabidopsis.
AtTPC1 has two conserved homologous domains, both of which contain six tran
smembrane segments (S1-S6) and a pore loop (P) between S5 and S6 in each do
main, and has the highest homology with the two pore channel TPC1 recently
cloned from rat. The overall structure is similar to the half of the genera
l structure of alpha -subunits of voltage-activated Ca2+ channels from anim
als. AtTPC1 rescued the Ca2+ uptake activity of a yeast mutant cch1. Sucros
e-induced luminescence, which reflects a cytosolic free Ca2+ increase in ae
quorin-expressing Arabidopsis leaves, was enhanced by overexpression of AtT
PC1 and suppressed by antisense expression of it. Sucrose-H+ symporters AtS
UC1 and 2, which depolarize membrane potential of cells receiving sucrose,
also depressed a Ca2+ increase by their antisense expression. These results
suggest that AtTPC1 mediates a voltage-activated Ca2+ influx in Arabidopsi
s leaf cells.