Abstract
In Arabidopsis, phosphatidylcholine (PC) is thought to be synthesized via the so-called nucleotide pathway, in which two isogenes for CTP:phosphorylcholine cytidylyltransferase, AtCCT1 (At2g32260) and AtCCT2 (At4g15130), play a regulatory role. We recently reported that PC accumulation in the rosettes of Arabidopsis at low temperature could be supported by selective enhancement of the expression of AtCCT2 (Inatsugi et al. (2002) Plant Cell Physiol. 43:1342-1350). To dissect further the differential roles of AtCCT isogenes, we isolated T-DNA-tagged mutants of AtCCT1 and AtCCT2 and designated cct1 and cct2, respectively. Construction of a cct1 cct2 double mutant that exhibited < 2% of the wild-type CCT activity in the rosettes revealed that such a low level of CCT activity is sufficient for normal growth and normal lipid composition. Alternatively, it is suggested that Arabidopsis contains uncharacterized pathways for PC biosynthesis that could compensate for the defect in the nucleotide pathway.
