ATP-dependent regulation of nuclear Ca(2+) levels in plant cells.
Localised alterations in cytoplasmic Ca(2+) levels are an integral part of the response of eukaryotic cells to a plethora of external stimuli. Due to the large size of nuclear pores, it has generally been assumed that intranuclear Ca(2+) levels reflect the prevailing cytoplasmic Ca(2+) levels. Using nuclei prepared from carrot (Daucus carota L.) cells, we now show that Ca(2+) can be transported across nuclear membranes in an ATP-dependent manner and that over 95% of Ca(2+) is accumulated into a pool releasable by the Ca(2+) ionophore A.23187. ATP-dependent nuclear Ca(2+) uptake did not occur in the presence of ADP or ADPgammaS and was abolished by orthovanadate. Confocal microscopy of nuclei loaded with dextran-linked Indo-1 showed that the initial ATP-induced rise in [Ca(2+)] occurs in the nuclear periphery. The occurrence of ATP-dependent Ca(2+) uptake in plant nuclei suggests that alterations of intranuclear Ca(2+) levels may occur independently of cytoplasmic [Ca(2+)] changes.
Bunney
T D
TD
Department of Cell Biology, John Innes Centre, Norwich Research Park, Colney Lane, NR4 7UH, Norwich, UK.
Shaw
P J
PJ
Watkins
P A
PA
Taylor
J P
JP
Beven
A F
AF
Wells
B
B
Calder
G M
GM
Drøbak
B K
BK
D000255:Adenosine Triphosphate / Q000378:metabolism*; D001693:Biological Transport, Active; D002118:Calcium / Q000378:metabolism*; D002467:Cell Nucleus / Q000378:metabolism*; D003593:Cytoplasm / Q000378:metabolism; D018552:Daucus carota / Q000378:metabolism; D007700:Kinetics; D018613:Microscopy, Confocal; D009685:Nuclear Envelope / Q000378:metabolism; D010944:Plants / Q000378:metabolism*
D000255:Adenosine Triphosphate; D002118:Calcium