Abstract
CTP:phosphorylcholine cytidylyltransferase (CCT, EC 2.7.7.15) is a rate-limiting enzyme in the CDP-choline pathway to phosphatidylcholine biosynthesis. In Arabidopsis thaliana, CCT is encoded by CCT1 and CCT2. We previously reported that the double knock-out mutant cct1-1 cct2 shows epigenetic homeosis that converted stamens and petals into carperoids and sepaloids, respectively (Sekiguchi et al., JSPP meeting, 2008). The mutant phenotypes resemble that of the B class gene mutants apetala3 and pistillata in the ABC flower morphogenesis model. Thus, B class genes might be down-regulated in cct1-1 cct2 mutants. We analyzed the transcript levels of APETALA3 (AP3) and PISTILLATA (PI) by RT-PCR and found that the level of AP3 transcripts is down-regulated in cct1-1 cct2 plants in parallel with the severity of homeosis. Methylation analysis showed that another AP3 promoter region that is located upstream of our previous region is highly methylated in cct1-1 cct2 plants. These results suggest that DNA methylation in the AP3 promoter causes epigenetic homeosis in cct mutants.
4Present address, Graduate School of Agricultural and Life Sciences, The University of Tokyo.
