신호전달체계.인산화효소.탈인산화효소.유전자기능.단백질 간 상호작용.signal transduction.protein kinase.protein phosphatase.gene function.protein-protein interaction.
초록▼
이 연구의 목적은 식물발달을 조절하는 신호전달체계의 분자적 기작을 이해하는 것이다. 이 연구를 통하여 식물발달 과정을 콘트롤하는 새로운 신호전달 유전자들을 발굴하며 각각의 신호전달 유전자 간의 상호작용을 탐구하므로서 식물발달 신호전달의 전체 네트워크를 이해하고자 하였다. 먼저 여러 식물조직 및 발생학적 시기의 신호전달 유전자를 동정하였고 northern blot analysis를 통하여 유전자발현을 탐구하였으며 여러 분자생물학적, 생화학적, 세포생물학적인 테크닉을 이용하여 신호전달 유전자와 단백질의 특성을 탐구하였다. 유전자의 식물
이 연구의 목적은 식물발달을 조절하는 신호전달체계의 분자적 기작을 이해하는 것이다. 이 연구를 통하여 식물발달 과정을 콘트롤하는 새로운 신호전달 유전자들을 발굴하며 각각의 신호전달 유전자 간의 상호작용을 탐구하므로서 식물발달 신호전달의 전체 네트워크를 이해하고자 하였다. 먼저 여러 식물조직 및 발생학적 시기의 신호전달 유전자를 동정하였고 northern blot analysis를 통하여 유전자발현을 탐구하였으며 여러 분자생물학적, 생화학적, 세포생물학적인 테크닉을 이용하여 신호전달 유전자와 단백질의 특성을 탐구하였다. 유전자의 식물발생관련 기능을 동정하기 위하여 RNAi, VIGS, 과대발현 등의 방법을 이용하였고 식물발생의 형태학적, 해부학적 연구를 수행하였다. Yeast two hybrid 방법을 이용하여 신호전달단백질 상호작용에 관하여 연구하였고 식물 기능유전체적인 방법을 이용하여 세포 내 신호전달 네트워크를 조사하였다. 이러한 연구를 통하여 mitochondrial hexokinase의 PCD 조절 기능 (Plant Cell 2006), mitochondrial prohibitin의 mitochondrial biogenesis조절 기능 (Plant J 2006), AXS1 유전자의 PCD 조절과 세포벽성분 RG-II 합성 조절 기능(JBC, 2006), IspE와 NbSiR의 엽록체 biogenesis 기능 (PMB, 2008, 2010), Rae1의 interphase와 mistosis 중의 기능 연구 (Plant J 2009) 등 15개의 논문을 발표함.
Abstract▼
The purpose of this study is to understand molecular mechanism of signal transduction pathways that regulate plant development. We planned to identify novel signaling components that modulate plant developmental porcesses, and to probe the protein-protein interaction in order to understand the globa
The purpose of this study is to understand molecular mechanism of signal transduction pathways that regulate plant development. We planned to identify novel signaling components that modulate plant developmental porcesses, and to probe the protein-protein interaction in order to understand the global picture of developmental signal transduction network. In this research, we identified plant signal transduction genes, analyzed various signal transduction genes and proteins using molecular and biochemical tools, analyzed expression of signal transduction genes, analyzed functions of plant signal transduction genes, and carried out protein-protein inteaction mapping to understand the cellular signaling network in plants. The results obtained in this projects were summarized below. Hexokinase is a major regulatory enzyme in sugar metabolism and sugar sensing in animals and plants. Recent findings suggest a pivotal role of mitochondria-associated hexokinase in the regulation of apoptosis in animal cells. In this study, virus-induced gene silencing (VIGS) of a hexokinase-encoding NbHxk1 caused necrotic lesions on leaves, abnormal leaf morphology, and retarded plant growth in Nicotiana benthamiana. NbHxk1 was associated with the mitochondria, and its N-terminal "membrane anchor" was required for this association. VIGS of NbHxk1 reduced the cellular glucose-phosphorylating activity to ~31% of control levels without changing the fructose-phosphorylating activity, and did not alter hexose phosphate content severely. The affected cells showed morphological markers of programmed cell death (PCD) including nuclear condensation and DNA fragmentation, accompanied by higher production of reactive oxygen species. Similar to apoptosis in animal systems, mitochondrial membrane potential decreased, cytochrome c was released into the cytosol, and caspase 9- and caspase 3-like proteolytic activities were strongly induced. Furthermore, based on flow cytometry, Arabidopsis plants overexpressing the Arabidopsis HXK1 and HXK2, both of which arepredominantly associated withmitochondria, exhibited enhanced resistance to $H_2O_2$-and a-picolinic acid-induced PCD. Finally, the addition of recombinant NbHxk1 to mitochondria-enriched fractions prevented $H_2O_2$/clotrimazole-induced cytochromec release and loss of mitochondrial membrane potential. Taken together, these results show that hexokinase critically regulates execution of PCD in plant cells, suggesting a link between glucose metabolism and apoptosis.
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