Distinct calcium signaling pathways regulate calmodulin gene expression in tobacco.
Cold shock and wind stimuli initiate Ca(2+) transients in transgenic tobacco (Nicotiana plumbaginifolia) seedlings (named MAQ 2.4) containing cytoplasmic aequorin. To investigate whether these stimuli initiate Ca(2+) pathways that are spatially distinct, stress-induced nuclear and cytoplasmic Ca(2+) transients and the expression of a stress-induced calmodulin gene were compared. Tobacco seedlings were transformed with a construct that encodes a fusion protein between nucleoplasmin (a major oocyte nuclear protein) and aequorin. Immunocytochemical evidence indicated targeting of the fusion protein to the nucleus in these plants, which were named MAQ 7.11. Comparison between MAQ 7.11 and MAQ 2.4 seedlings confirmed that wind stimuli and cold shock invoke separate Ca(2+) signaling pathways. Partial cDNAs encoding two tobacco calmodulin genes, NpCaM-1 and NpCaM-2, were identified and shown to have distinct nucleotide sequences that encode identical polypeptides. Expression of NpCaM-1, but not NpCaM-2, responded to wind and cold shock stimulation. Comparison of the Ca(2+) dynamics with NpCaM-1 expression after stimulation suggested that wind-induced NpCaM-1 expression is regulated by a Ca(2+) signaling pathway operational predominantly in the nucleus. In contrast, expression of NpCaM-1 in response to cold shock is regulated by a pathway operational predominantly in the cytoplasm.
van Der Luit
A H
AH
Institute for Molecular Cell Biology, University of Amsterdam, Kruislaan 318, 1098 SM Amsterdam, The Netherlands. luit@bio.uva.nl
Olivari
C
C
Haley
A
A
Knight
M R
MR
Trewavas
A J
AJ
D000331:Aequorin / Q000096:biosynthesis / Q000235:genetics; D001483:Base Sequence; D002118:Calcium / Q000502:physiology*; D002147:Calmodulin / Q000737:chemistry / Q000235:genetics*; D018506:Gene Expression Regulation, Plant; D017343:Genes, Plant; D008969:Molecular Sequence Data; D030821:Plants, Genetically Modified; D010947:Plants, Toxic; D020033:Protein Isoforms / Q000737:chemistry / Q000235:genetics; D011994:Recombinant Proteins / Q000096:biosynthesis / Q000737:chemistry; D016415:Sequence Alignment; D017386:Sequence Homology, Amino Acid; D015398:Signal Transduction / Q000502:physiology*; D014026:Nicotiana / Q000235:genetics* / Q000378:metabolism*
D002147:Calmodulin; D020033:Protein Isoforms; D011994:Recombinant Proteins; D000331:Aequorin; D002118:Calcium