Abstract
Arabidopsis contains two isogenes for CTP:phosphorylcholine cytidylyltransferase (CCT), AtCCT1 and AtCCT2, whose contribution to the enhanced biosynthesis of phosphatidylcholine (PC) at low temperature remains to be genetically evaluated. We previously reported that T-DNA-tagged disruption of AtCCT2 scarcely affected the accumulation of PC at low temperature, despite the selective enhanement of AtCCT2 expression in wild type at low temperature.
Here we revealed that AtCCT1 contributes to the enhancement of CCT activity at low temperature without significant enhancement of expression levels in this disruptant. We examined the distribution of CCT activity and AtCCT1 protein in differentially centrifugated fractions of rosette homogenates and found that enhancement of the CCT activity in the 150 k x g pellet fraction at low temperature accompanies little increase of AtCCT1 protein. These results suggested that both of the two CCT isogenes of Arabidopsis contribute to the activation of PC biosynthesis at low temperatures by different mechanisms.
