Abstract
In A. thaliana, CTP:phosphorylethanolamine cytidyltransferase (PECT1; EC 2.7.7.14) regulates phosphatidylethanolamine (PE) biosynthesis via the CDP-ethanolamine pathway. We previously reported that pect1-4 mutants show growth retardation at 8oC (Mizoi et al. 2006). Because PE is the major mitochondrial phospholipid and PECT1 is localized on the outer surface of mitochondria, we investigated the effects of pect1-4 on the respiration capacity of isolated mitochondria. We found that pect1-4 mitochondria showed decreased total respiration (TOR) capacity due to decreased cytochrome oxidase pathway (COP) capacity compared to wild-type mitochondria. When plants were subjected to 8oC, TOR capacity transiently decreased in both wild-type and pect1-4 mitochondria after 3 d mainly due to decreases in COP capacity. After 14 d at 8oC, TOR capacity resumed with increasing COP capacity in wild-type and pect1-4 mitochondria. However, the difference between TOR and COP significantly decreased in pect1-4 mitochondria compared to that before cold treatment. The results will be discussed with respect to adjustment of the alternative oxidase pathway capacity in pect1-4 mutants at 8oC.
