The role of an expansin gene (IbEXP1) in the formation of the storage root (SR) was investigated by expression pattern analysis and characterization of IbEXP1-antisense sweetpotato (Ipomoea batatas cv.Yulmi) plants in an attempt to elucidate the molecular mechanism underlying SR development in sweetpotato. Transcript level of IbEXP1 was high in the fibrous root (FR) and petiole at the FR stage, but decreased significantly at the young storage root (YSR) stage. IbEXP1-antisense plants cultured in vitro produced FRs which were both thicker and shorter than those of wild-type (WT) plants. Elongation growth of the epidermal cells was significantly reduced, and metaxylem and cambium cell proliferation was markedly enhanced in the FRs of IbEXP1-antisenseplants, resulting in an earlier thickening growth in these plants relative to WT plants. There was a marked reduction in the lignification of the central stele of the FRs of the IbEXP1-antisense plants, suggesting that the FRs of the mutant plants possessed a higher potential than those of WT plants to develop into SRs. IbEXP1-antisense plants cultured in soil produced a larger number of SRs and, consequently, total SR weight per IbEXP1-antisense plant was greater than that per WT plant. These results demonstrate that SR development was accelerated in IbEXP1-antisense plants and suggest that IbEXP1 plays a negative role in the formation of SR by suppressing the proliferation of metaxylem and cambium cells to inhibit the initial thickening growth of SRs.

Embryonic stem (ES) cells can self-renew maintaining the undifferentiated state. Self renewal requires many factors such as Oct4, Sox2, FoxD3, and Nanog. NF- is a transcription factor involved in many biological activities. Expression and activity of NF- increase upon differentiation of ES cells. Reportedly, Nanog protein directly binds to NF- protein and inhibits its activity in ES cells. Here, we found a potential binding site of NF- in the human Nanog promoter and postulated that NF- protein may regulate expression of the Nanog gene. We used human embryonic carcinoma (EC) cells as a model system of ES cells and confirmed decrease of Nanog and increase of NF- upon differentiation induced by retinoic acid. Although deletion analysis on the DNA fragment including NF- binding site suggested involvement of NF- in the negative regulation of the promoter, site-directed mutation of NF- binding site had no effect on the Nanog promoter activity. Furthermore, no direct association of NF- with the Nanog promoter was detected during differentiation. Therefore, we conclude that NF- protein may not be involved in transcriptional regulation of Nanog gene expression in EC cells and possibly in ES cells.

배아 줄기세포는 미분화상태에서 자가 재생을 유지할 수 있다. 자가 재생은 OCT4, SOX2와 NANOG와 같은 많은 인자들이 작용한다. 생쥐 배아 줄기세포에서 OCT4와 SOX2가 Nanog 프로모터에 결합하여 Nanog 유전자의 발현을 촉진한다는 사실은 생쥐 promoter에 관한 정밀분석으로 알려져 있다. 본 연구에서는 인간 Nanog promoter를 정밀 분석하기 위해 연속적인 결손 돌연변이를 가진 promoter-reporter constru

포배의 착상은 구조 및 기능적으로 준비된 자궁내막의 체계적 반응에 의하여 진행되는데, 자궁 내막에서 엄격히 통제된 급격한 세포의 증식과 분화가 진행된다. 구강 상피세포암의 억제자로 알려진 Doc-1이 자궁에서 스테로이드 호르몬에 의하여 발현되며 세포 증식을 조절할 것으로 추정되어 왔으나, 그 정확한 발현 변화에 대한 이해가 불충분하였다. 따라서 본 연구에서는 체외에서 탈락막 반응 모델 확립을 통하여 세포의 증식과 분화 진행과정에서 Doc-1의 발현 조절

Ascorbate peroxidase (APX) plays a crucial role in the detoxification of hydrogen peroxide. APX activity is maintained significantly higher in the paraquat­treated leaves of the paraquat-tolerant Rehmannia glutinos. This study was conducted to understand structural and regulatory characteristics of APX gene in R. glutinosa. A putative APX cDNA clone (RgAPX1) was isolated from a leaf cDNA library using a partially sequenced expressed sequence tag clone. RgAPX1 is consisted of 1148 bp nucleotides and contains an open reading frame encoding a 250 amino acid-long polypeptide. Deduced RgAPX1 amino acid sequence shares higher sequence similarity to cytosolic APXs. RgAPX1. expression was higher in the leaf than in the flower and root. Southern blot result indicates the presence of one or two RgAPX1-related genes in R. glutinosa genome. RgAPX1 transcription was affected differentially by various stresses and phytohormone. The results indicate that RgAPXl is constitutively expressed in most tissues and its expression is modulated for the immediate and efficient detoxification of H2O2 under normal and stress conditions.

내분비계 장애물질은 다양한 동물의 생식과 배아의 발생에 위해한 영향을 미친다고 보고되었다. 이러한 초기 배아의 비정상 발생 중 대표적인 것이 할구파편이다. 본 연구에서는 착상 전 생쥐 초기 배아를 PCB, BPA, DDT에 체내, 체외에서 각각 노출시켰다. 내분비계 장애 물질에 노출시켰던 배아는 할구파편, 불규칙한 할구와 깨짐, 일부 파괴된 투명대 배아 등의 다양한 형태학적 비정상 양상을 보였다. 착상 전 생쥐 초기배아의 세포괴사에 관여하는 유전자를 조

환경에 방출되어 있는 많은 내분비교란물질들은 사람과 동물의 내분비계에 교란을 일으킬 수 있는 잠재력을 가진다. 뇌의 성분화는 생식소 호르몬 영향하에 비가역적으로 진행되며 흰쥐의 경우 이 시기는 임신말기에서 생후 7∼10일 가량이다. 최근에 본 연구진은 횐쥐의 뇌 성 분화의 결정적인 시기에 발현되는 KAP3유전자를 클로닝하였다 (Choi ＆ Lee, 1999). KAP3의 기능은 신경세포를 포함한 세포에서 aronal tansport를 조절하는 것으로 알