Cold-shock regulation of the Arabidopsis TCH genes and the effects of modulating intracellular calcium levels.
The Arabidopsis TCH genes, which encode calmodulin-related proteins and a xyloglucan endotransglycosylase, are shown to be up-regulated in expression following cold shock. We investigated a possible role of fluctuations in intracellular calcium ion concentrations ([Ca2+]) in the cold-shock-induced TCH gene expression. Transgenic plants harboring the apoaequorin gene were generated to monitor [Ca2+]) and to test the necessity of cold-induced [Ca2+] increases for TCH expression. Cold-shock-induced [Ca2+] increases can be blocked by La3+ and Gd3+, putative plasma membrane Ca2+ channel blockers, and 1,2-bis(o-aminophenoxy)ethane-N,N,N',N'-tetraacetic acid, an extracellular Ca2+ chelator. Cold-shock-induced expression of the TCH genes is inhibited by levels of La3+, Gd3+, and 1,2-bis(o-aminophenoxy)ethane-N,N,N',N'-tetraacetic acid, that have been shown to block [Ca2+] increases. These data support the hypotheses that (a) intracellular [Ca2+] increases following cold shock require extracellular Ca2+ and may derive from a Ca2+ influx mediated by plasmalemma Ca2+ channels, and (b) cold up-regulation of expression of at least a subset of the TCH genes requires an intracellular [Ca2+] increase. The inhibitors are also shown to have stimulus-independent effects on gene expression, providing strong evidence that these commonly used chemicals have more complex effects than generally reported.
Polisensky
D H
DH
Department of Biochemistry and Cell Biology, Rice University, Houston, Texas 77005-1892, USA.
Braam
J
J
D017360:Arabidopsis / Q000235:genetics*; D002118:Calcium / Q000378:metabolism*; D002121:Calcium Channel Blockers / Q000494:pharmacology; D002147:Calmodulin / Q000378:metabolism; D002614:Chelating Agents / Q000494:pharmacology; D003080:Cold Temperature; D018506:Gene Expression Regulation, Plant / Q000187:drug effects; D016695:Glycosyltransferases / Q000235:genetics*; D010940:Plant Proteins / Q000235:genetics*
D002121:Calcium Channel Blockers; D002147:Calmodulin; D002614:Chelating Agents; D010940:Plant Proteins; D016695:Glycosyltransferases; C073693:xyloglucan endotransglycosylase; D002118:Calcium