酵母细胞凋亡研究进展

细胞凋亡是调节生物体正常发育和生命活动的一种不可缺少的机制,其研究生命力在于最终能够有利于疾病机制的阐明以及新疗法的探索及问世。酵母细胞由于凋亡过程的高度保守性及其作为分子生物学模式物种的先天优势,近年来一直是凋亡研究的热点。目前对酵母细胞凋亡的核心分子、传导通路和诱因等已经有了深入的了解。     

酵母细胞凋亡机制研究进展

凋亡是一种主动有序发生、受多基因严密控制的细胞逐渐死亡过程,对维持机体正常的生命活动发挥着重要作用,酵母因能发生细胞凋亡且凋亡机制与哺乳动物细胞相比具有高度保守性而成为研究细胞凋亡的重要模式生物。综述近年来酵母细胞凋亡的关键调节因子、启动机制和信号通路的研究进展,并展望其潜在应用前景。     

叶片衰老的特性及分子调控（综述）

就叶片衰老研究在生理,生化及分子水平上的最新进展,以及有希望应用于农业,操纵叶片衰老的转基因手段作一简要综述。     

生物衰老的主要分子机制概述

衰老是一种包括生理性衰老和病理性衰老的正常自然规律,与其他生物过程一样,受一些信号通路和分子机制的调控。研究发现调控生物衰老机制的信号通路之间存在相互作用。综述了胰岛素通路、雷帕霉素通路及Sirtuins家族这3种与自噬相关的延缓衰老的经典信号通路,总结了氧化应激、细胞衰老、免疫衰老等影响机体衰老的主要原因及方式,希望在此基础上发现新的互作通路,探索出更多新颖的分子机制和方法以预防、延缓或减轻多种与衰老相关的疾病。     

叶片衰老的特性及分子调控(综述)

就叶片衰老研究在生理、生化及分子水平上的最新进展,以及有希望应用于农业的、操纵叶片衰老的转基因手段作一简要综述。     

酵母细胞周期调控的研究进展

酵母是一种研究细胞周期调控的好材料,在细胞周期的调控研究中具有重要作用。现在通常以芽殖酵母和裂殖酵母为代表进行研究。这两种酵母的细胞周期进程与高等真核生物相比各有其特点。 酵母细胞周期运行中存在有三个不同的控制点,即start点、S期启动点、G2/M转换处。在这三个不同的控制点起作用的CDK的组成是不同的。芽殖酵母分别是Cdc28-Clns;Cdc28-Clb5和Cdc28-Clb6;Cdc28-Clb1、Cdc28-Clb2、Cdc28-Clb3和Cdc28-Clb4。裂殖酵母中分别是Cdc2-Cig2;Cdc2-Cig2;Cdc2-Cdc13和Cdc2-Cig1,其中芽殖酵母中的Cdc28和裂殖酵母中的cdc2是等效基因。不同的控制点存在着不同 的调控机制,它们涉及到大量的基因,其中以G2/M转换处的调控机制研究得最早也最透彻。另外,APC途径在M中期/后期转化中起着重要作用。     

植物衰老的分子基础与调控

综述了植物衰老过程中的基因表达的上调和下调两种趋势,以及目前延缓植物衰老的调控手段。     

外源ipt对叶片衰老分子调控研究进展(综述)

综述了叶片衰老的分子机理,并介绍了将外源异戊烯基转移酶（ipt,isopentenyl transferase)基因转入植物以获得抗衰老植株的研究进展。     

啤酒废酵母生物营养素的研究进展

啤酒废酵母生物营养素的研究进展林宇野（福建师范大学微生物工程所，福州）杨虹，史美榕（福州大学轻工业系，福州）据统计，１９９３年我国已成为世界生产啤酒的第二大国，年产啤酒超过１３００万吨，约占世界总产量２％左右。啤酒工业的飞速发展，也带来了大量副产物─...     

衰老相关microRNAs研究进展

microRNAs(miRNAs)是一类长度约22个核苷酸的非编码RNA.这是一种广泛存在于真核生物中的内源性单链小分子RNA,miRNAs通过部分碱基对互补方式与靶基因结合,在转录和转录后水平调节靶基因表达.最近研究发现,miRNAs可以靶向多个衰老相关信号通路,在线虫、果蝇、小鼠和人类的衰老过程中发挥了重要的调控作用.本文总结了近年来与衰老相关的miRNAs的研究进展,首先介绍衰老相关的信号通路,然后重点介绍与线虫和哺乳动物衰老有关的miRNAs,以及这些miRNAs如何调控衰老相关信号通路,从而影响细胞、组织和整个机体的衰老进程和衰老相关性疾病,最后展望该领域未来的研究方向.     

A dominant interfering mutation in RAS1 of Saccharomyces cerevisiae

A mutant allele of RAS1 that dominantly interferes with the wild-type Ras function in the yeast Saccharomyces cerevisiae was discovered during screening of mutants that suppress an ira2 disruption mutation. A single amino acid substitution, serine for glycine at position 22, was found to cause the mutant phenotype. The inhibitory effect of the RAS1 ^Ser22 gene could be overcome either by overexpression of CDC25 or by the ira2 disruption mutation. These results suggest that the RAS1^Ser22 gene product interferes with the normal interaction of Ras with Cdc25 by forming a dead-end complex between Ras1^Ser22 and Cdc25 proteins.     

代谢工程改造酿酒酵母提高法尼醇产量

[目的]法尼醇(FOH,C15H26O)是一种具有芳香气味的非环状倍半萜醇,被广泛应用于化妆品和医学药物的工业化生产,也可作为航空燃料的理想替代品.具有食品级安全性的酿酒酵母细胞能够合成内源性法尼醇,但其产量很低,无法满足工业生产的需要.因此,需要采用代谢工程手段,改造法尼醇合成途径,以有效提高法尼醇在酿酒酵母中的产量...     

Cloning and characterization of seven cDNAs for hyperosmolarity-responsive (HOR) genes of Saccharomyces cerevisiae

Yeast cells can respond and adapt to osmotic stress. In our attempt to clarify the molecular mechanisms of cellular responses to osmotic stress, we cloned seven cDNAs for hyperosmolarity-responsive (HOR) genes from Saccharomyces cerevisiae by a differential screening method. Structural analysis of the clones revealed that those designated HOR1, HORS, HOR4, HOR5 and HOR6 encoded glycerol-3-phosphate dehydrogenase (Gpd1p), glucokinase (Glklp), hexose transporter (Hxtlp), heat-shock protein 12 (Hsp12p) and Na⁺, K⁺, Li⁺-ATPase (Enalp), respectively. HOR2 and HOR7 corresponded to novel genes. Gpdlp is a key enzyme in the synthesis of glycerol, which is a major osmoprotectant in S. cerevisiae. Cloning of HOR1/GPD1 as a HOR gene indicates that the accumulation of glycerol in yeast cells under hyperosmotic stress is, at least in part, caused by an increase in the level of GPDH protein. We performed a series of Northern blot analyses using HOR cDNAs as probes and RNAs prepared from cells grown under various conditions and from various mutant cells. The results suggested that all the HOR genes are regulated by common signal transduction pathways. However, the fact that they exhibited certain distinct responses indicated that they might also be regulated by specific pathways in addition to the common pathways. Ca²⁺ seemed to be involved in the signaling systems. In addition, Hog1p, one of the MAP kinases in yeast, appeared to be involved in the regulation of expression of HOR genes, although its function seemed to be insufficient for the overall regulation of expression of these genes.     

酿酒酵母全基因组范围内筛选MTM1基因的抑制基因

MTM1 基因对于维持锰超氧化物歧化酶的活性和线粒体正常功能十分重要,MTM1 基因的缺失会严重影响酵母锰超氧化物歧化酶活性,并损伤线粒体功能,因此在非发酵培养基上不能生长．利用MTM1 基因缺失的突变体在非发酵培养基上的生长缺陷,转入酵母基因组文库筛选MTM1 抑制基因,发现MTM1基因缺失造成的损伤一旦形成不可逆转,重新引入MTM1 基因也无法挽救,直接筛选无法得到抑制基因．为了避免MTM1缺失造成的不可逆损伤,在野生型酵母中先转入带有MTM1 基因的质粒,再敲除染色体上的MTM1 基因,随后转入基因组文库,再利用药物5-氟乳清酸(5-FOA)迫使细胞丢失表达MTM1基因的外源质粒,再筛选能在非发酵培养基上生长的转化子,通过这种方法筛选发现,POR2等5个基因的过表达可以挽救MTM1 基因缺失造成的非发酵培养基上的生长缺陷,为深入了解MTM1基因的功能提供了线索,对筛选其他造成不可逆损伤的突变基因的抑制基因提供了一条可行的研究思路．     

酵母Sirtuins在细胞寿命中的作用

酿酒酵母(以下简略为酵母)作为寿命分析模型广泛应用于寿命研究领域。酵母寿命分析方法有两种,分别是复制型酵母寿命分析法和时序型酵母寿命分析法。目前,通过酵母寿命分析模型已识别出包括SIR2在内的多个寿命调节基因。SIR2是目前较好的被确立起来的寿命调节基因,具有NAD依赖型脱乙酰化酶的活性,从原核生物到真核生物都有良好的保守性。Sirtuins (Sir2蛋白家族的总称)在细胞内具有功能上的多样性,其中包括对于压力耐受的调节、基因转录的调节、代谢通路的调节以及寿命调节作用等。Sir2是Sirtuins家族最早发现的成员,其功能是参与异染色质结构域转录的沉默调节,同时还参与复制型酵母寿命的调节。已证明,SIR2的缺失会缩短酵母的寿命,基因表达的增高会延长寿命。Sir2的高等真核生物的同源蛋白也被证实参与衰老相关疾病的调节。本文中,我们将阐述Sir2以及Sir2的酵母同源蛋白Hst1-Hst4的功能,以及由它们调节的酵母寿命。     

利用酿酒酵母转座子文库筛选线粒体镁代谢相关基因

镁离子对于维持细胞正常功能十分重要,糖尿病、高血压、慢性呼吸道疾病、骨质疏松、心律失常等多种疾病都与镁代谢失衡有关．MRS2 基因编码线粒体镁离子转运蛋白,MRS2缺失会导致酵母线粒体镁离子浓度下降、线粒体内Ⅱ型内含子剪接缺陷和非发酵碳源培养基上的生长缺陷．为了增进对线粒体镁离子代谢调控基因的了解,利用酿酒酵母mTn-lacZ/LEU2转座子文库筛选MRS2的抑制基因,发现线粒体载体家族成员YMR166C基因的缺失可以挽救MRS2基因缺失突变体的生长缺陷、Ⅱ型内含子剪接缺陷,并可以调节线粒体镁离子浓度,首次发现YMR166C是线粒体镁代谢相关基因.     

Plasmid stability in recombinant Saccharomyces cerevisiae

Because of many advantages, the yeast Saccharomyces cerevisiae is increasingly being employed for expression of recombinant proteins. Usually, hybrid plasmids (shuttle vectors) are employed as carriers to introduce the foreign DNA into the yeast host. Unfortunately, the transformed host often suffers from some kind of instability, tending to lose or alter the foreign plasmid. Construction of stable plasmids, and maintenance of stable expression during extended culture, are some of the major challenges facing commercial production of recombinant proteins. This review examines the factors that affect plasmid stability at the gene, cell, and engineering levels. Strategies for overcoming plasmid loss, and the models for predicting plasmid instability, are discussed. The focus is on S. cerevisiae, but where relevant, examples from the better studied Escherichia coli system are discussed. Compared to free suspension culture, immobilization of cells is particularly effective in improving plasmid retention, hence, immobilized systems are examined in some detail. Immobilized cell systems combine high cell concentrations with enhanced productivity of the recombinant product, thereby offering a potentially attractive production method, particularly when nonselective media are used. Understanding of the stabilizing mechanisms is a prerequisite to any substantial commercial exploitation and improvement of immobilized cell systems.     

Crabtree-negative characteristics of recombinant xylose-utilizing Saccharomyces cerevisiae

For recombinant xylose-utilizing Saccharomyces cerevisiae, ethanol yield and productivity is substantially lower on xylose than on glucose. In contrast to glucose, xylose is a novel substrate for S. cerevisiae and it is not known how this substrate is recognized on a molecular level. Failure to activate appropriate genes during xylose-utilization has the potential to result in sub-optimal metabolism and decreased substrate uptake. Certain differences in fermentative performance between the two substrates have thus been ascribed to variations in regulatory response. In this study differences in substrate utilization of glucose and xylose was analyzed in the recombinant S. cerevisiae strain TMB3400. Continuous cultures were performed with glucose and xylose under carbon- and nitrogen-limited conditions. Whereas biomass yield and substrate uptake rate were similar during carbon-limited conditions, the metabolic profile was highly substrate dependent under nitrogen-limited conditions. While glycerol production occurred in both cases, ethanol production was only observed for glucose cultures. Addition of acetate and 2-deoxyglucose pulses to a xylose-limited culture was able to stimulate transient overflow metabolism and ethanol production. Application of glucose pulses enhanced xylose uptake rate under restricted co-substrate concentrations. Results are discussed in relation to regulation of sugar metabolism in Crabtree-positive and -negative yeast.