Oct4 and Nanog are well-known transcription factors related with self renewal of embryonic stem cell. In low-dose of Nanog, transcription of oct4 is increased; however, oct4 is down-regulated upon high-dose of Nanog. There is a negative feedback loop between oct4 and Nanog. To identify this regulation, we generated 4 nested sets for mouse oct4 promoter. Luciferase activities of oct4 were declined upon high-dose Nanog in all constructs. The declined effects of oct4 upon high-dose Nanog were moderated with DNMT and HDAC inhibitors (5-AZA-cytidine and trichostatin A) in 3 constructs (1867, 1346, 754). But, one construct (2179) was only sensitive to TSA. Taken together, these effects were also represented in semi-quantitative RT-PCR and Western blotting data. These data suggest that negative regulation of oct4 gene upon high-dose Nanog would be accomplished by DNMT and HDAC. Further, it will be studied whether these constraining molecules bind to CR1-4 region of oct4 promoter upon low- and high-dose of Nanog.

There is a growing number of plant genomes that are being sequenced, but most of these available assemblies do not cover the entire genome mainly due to the highly repetitive sequences found in most plant genomes. Nevertheless, these repeats, although a challenge in assembly algorithms, provide relevant information about a genome’s history that could help explain its structure and complexity. Here, we cytogenetically mapped previously and presently characterized major repeats of Panax ginseng genome, including several LTR retrotransposons (PgDel2, PgDel3, PgTat1, PgTat2, PgTork) and one tandem repeat, PgTR Fluorescence in situ hybridization (FISH) results showed differential accumulation of Ty3/gypsy LTR retrotransposons into different chromosomal regions or subgenomes, suggesting a non-random preferential amplification of retrotransposons in these regions and an allopolyploid origin of P. ginseng. In silico analysis based on 1x whole genome sequence reads suggests that PgTR is the most abundant tandem repeat in ginseng, which was further corroborated by FISH analysis. More importantly, its unique distribution pattern among the 24 ginseng chromosomes, coupled with the non-random distribution of LTR retrotransposons and rDNA arrays, allowed us to discriminate and characterize each individual ginseng chromosome. These different newly characterized cytogenetic markers allowed reorganization of previously reported ginseng karyotype with better resolution, demonstrating the irutility in ginseng chromosome identification. These information give us insight about the genomic structure of P. ginseng, and should be useful for future comparative cytogenetics studies among closely related species to unravel its genomic history. This work was supported by the Next-Generation BioGreen21 Program (No. PJ008202), Rural Development Administration, Republic of Korea.