第六届九源奖学金一等奖论文摘要（1）

1、Leucyl-tRNA Synthetase Consisting of Two Subunits from Hyperthermophilic Bacteria Apuifex aeolicus（论文发表：The Journal of Biological Chemistry）

In a hyperthermophilic bacterium, Aquifex aeolicus, leucyl-tRNA synthetase (LeuRS) consists of two non-identical polypeptide subunits (α and β),different from the canonical LeuRS, which has a single polypeptide template, genes encoding theαand βsubunits were amplified and cloned in Escherichia coli. The α subunit could not be expressed stably in vivo, whereas the β subunit was overproduced and purified by a simple procedure. The β subunit was inactive in catalysis but was able to bind tRNA LEU .Interestingly, the heterodimerαβ-LeuRS could be overproduced in E. coli cells containing both genes and was purified to 95% homogeneity as a hybrid dimer. The kinetics of A. aeolicus LeuRS in presteady and steady states and cross-recognition of Leurs and Trnaleu from A. aeolicus and E. coli were studied. Magnesium concentration, pH value, and temperature aminoacylation optima were determined to be 12mM,7.8, and 70℃, respectively. Under optimal conditions A. aeolicus αβ-LeuRS is stable up to 65℃.

作者：徐敏刚 （中科院生化细胞所攻读博士学位，师从王恩多研究员，专业、特长：生物化学，分子生物学。）

Acetylcholinesterase (AChE) plays a key role in terminating neurotransmission at cholinergic synapses. AchE is also found in tissues devoid of cholinergic responses, indicating potential functions beyond neurotransmission. It has been suggested that AChE may participate in development, differentiation, and pathogenic processes such as Alzheimer's disease and tumorigenesis. We examined AChE expression in a number of cell lines upon induction of apoptosis by various stimuli. AChE is induced in all apoptotic cells examined as determined by cytochemical staining, immunological analysis, affinity chromatography purification, and molecular cloning. The AChE protein was found in the cytoplasm at the initiation of apoptosis and them in the nucleus or apoptotic bodies upono commitment to cell death, Sequence analysis revealed that AChE expressed in apoptotic cells is identical to the synapse type AChE. Pharmacological ingibitors of AChE prevented apoiptosis. Furthermore, blocking the expression of AChE with antisense inhibited apoptosis. Therefore, blocking the expression of AChE with antisense inhibited apoptosis. Therefore, our studies demonstrate that AChE is potentially a marker and a rugulator of apoptosis.

作者：杨磊 （中科院生化细胞所攻读博士学位，师从张学军研究员，专业特长：分子细胞生物学）。

3、Silencing of Phosphoethanolamine N-Methyltransferase Results in Temperature-Sensitive Male Sterility and SaltHypersensitivity in Arabidopsis （发表杂志：The Plant Cell, Vol. 14,2031-2043）

S-Adenosyl-L-methionine:phosphoethanolamine N-methyltransferase (PEAMT; EC 2.1.1.103) catalyzes the key step in choline (Cho) biosynthesis, the N-methylation of phosphoethanolamine. Cho is a vital precursor of the membrane phospholipid phosphatidylcholine, which accounts for 40 to 60% of lipids in nonplastid plant membranes. Certain plants use Cho to produce the osmoprotectant glycine betaine, which confers resistance to salinity, drought, and other stresses. An Arabidopsis mutant, t365, in which the PEAMT gene is silenced, was identified using a new sense/antisense RNA expression system. t365 mutant plants displayed multiple morphological phenotypes, including pale-green leaves, early senescence, and temperature-sensitive male sterility. Moreover, t365 mutant plants produced much less Cho and were hypersensitive to salinity. These results demonstrate that Cho biosynthesis not only plays an important role in plant growth and development but also contributes to tolerance to environmental stresses. The temperature-sensitive male sterility caused by PEAMT silencing may have a potential application in agriculture for engineering temperature-sensitive male sterlity in important crop plants.

作者：王晓群 （中科院遗传与发育生物学研究所攻读博士学位，师从李家洋院士，专业特长：高等植物的生长发育与代谢的分子遗传学）。

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