Investigation of tRNA<Superscript>Leu/Lys</Superscript> and ATPase 6 Genes Mutations in Huntington’s Disease

Huntington disease (HD) is a genetically dominant condition caused by expanded CAG repeats which code for glutamine in the HD gene product, huntingtin. Huntingtin is expressed in almost all tissues, so abnormalities outside the brain can also be expected. Involvement of nuclei and mitochondria in HD pathophysiology has been suggested. In fact mitochondrial dysfunction is reported in brains of patients suffering from HD. The tRNA gene mutations are one of hot spots that can cause mitochondrial disorders. In this study, possible mitochondrial DNA (mtDNA) damage was evaluated by screening for mutations in the tRNA^leu/lys and ATPase 6 genes of 20 patients with HD, using PCR and automated DNA sequencing. Mutations including an A8656G mutation in one patient were observed, which may be causal to the disease. Understanding the role of mitochondria in the pathogenesis of neurodegenerative diseases could potentially be important for the development of therapeutic strategies in HD.     

Genomic signature of natural and anthropogenic stress in wild populations of the waterflea Daphnia magna: validation in space, time and experimental evolution

Natural populations are confronted with multiple selection pressures resulting in a mosaic of environmental stressors at the landscape level. Identifying the genetic underpinning of adaptation to these complex selection environments and assigning causes of natural selection within multidimensional selection regimes in the wild is challenging. The water flea Daphnia is a renowned ecological model system with its well-documented ecology, the possibility to analyse subfossil dormant egg banks and the short generation time allowing an experimental evolution approach. Capitalizing on the strengths of this model system, we here link candidate genome regions to three selection pressures, known to induce micro-evolutionary responses in Daphnia magna: fish predation, parasitism and land use. Using a genome scan approach in space, time and experimental evolution trials, we provide solid evidence of selection at the genome level under well-characterized environmental gradients in the wild and identify candidate genes linked to the three environmental stressors. Our study reveals differential selection at the genome level in Daphnia populations and provides evidence for repeatable patterns of local adaptation in a geographic mosaic of environmental stressors fuelled by standing genetic variation. Our results imply high evolutionary potential of local populations, which is relevant to understand the dynamics of trait changes in natural populations and their impact on community and ecosystem responses through eco-evolutionary feedbacks.     

Comparison of the ribosomal RNA genes in four closely relatedCucurbitaceae

Cucurbitaceae are characterized by a high copy number for nuclear ribosomal RNA genes. We have investigated the genomic ribosomal DNA (rDNA) of four closely related species of this family with respect to structure, length heterogeneity, and evolution. InCucumis melo (melon) there are two main length variants of rDNA repeats with 10.7 and 10.55kb.Cucumis sativus (cucumber) shows at least three repeat types with 11.5, 10.5, and 10.2kb.Cucurbita pepo (zucchini) has two different repeat types with 10.0 and 9.3kb. There are also two different repeat types inCucurbita maxima (pumpkin) of about 11.2 and 10.5kb. Restriction enzyme mapping of the genomic rDNA of these four plants and of cloned repeats ofC. sativus shows further heterogeneities which are due to methylation or point mutations. By comparison of the restriction enzyme maps it was possible to trace some evolutionary events in the family ofCucurbitaceae. Some aspects of regulation and function of the middle repetitive rRNA genes (here between 2000 and 10000 copies) are discussed.     

Quox-1基因同源序列在人胚早期发育中的表达

以Quox-1基因的特异性片段b_2为探针,与人基因组DNA作Southern杂交,结果显示,人基因组中存在Quox-1基因的同源序列。以抗Quox-1蛋白的抗体与早期人胚胎组织的切片作免疫组化反应研究了Quox-1基因同源序列在人胚早期发育过程中的表达,结果表明其表达有明显的时间和空间特异性。胚龄30天以前,Quox-1基因的同源序列在人胚包括神经管等许多部位表达,30天以后表达部位局限于脊索、心肌细胞、生肌节、消化道上皮及周皮等处。文中讨论了Quox-1基因同源顺序对人类胚胎早期发育过程可能的调控作用。     

Structural and functional insights into the modulation of the activity of a flax cytokinin oxidase by flax rust effector AvrL567-A

During infection, plant pathogens secrete effector proteins to facilitate colonization. In comparison with our knowledge of bacterial effectors, the current understanding of how fungal effectors function is limited. In this study, we show that the effector AvrL567-A from the flax rust fungus Melampsora lini interacts with a flax cytosolic cytokinin oxidase, LuCKX1.1, using both yeast two-hybrid and in planta bimolecular fluorescence assays. Purified LuCKX1.1 protein shows catalytic activity against both N6-(Δ2-isopentenyl)-adenine (2iP) and trans-zeatin (tZ) substrates. Incubation of LuCKX1.1 with AvrL567-A results in increased catalytic activity against both substrates. The crystal structure of LuCKX1.1 and docking studies with AvrL567-A indicate that the AvrL567 binding site involves a flexible surface-exposed region that surrounds the cytokinin substrate access site, which may explain its effect in modulating LuCKX1.1 activity. Expression of AvrL567-A in transgenic flax plants gave rise to an epinastic leaf phenotype consistent with hormonal effects, although no difference in overall cytokinin levels was observed. We propose that, during infection, plant pathogens may differentially modify the levels of extracellular and intracellular cytokinins.     

甘蓝型油菜芥酸和二十碳烯酸含量的基因效应

以甘蓝型油菜的4种纯合芥酸基因型之间所有可能的6个杂交组合的P_1、P_2、F_1、P_2、B_1和B_2世代为材料,用生统遗传学方法研究了芥酸和二十碳烯酸的基因作用形式及效应。发现无论亲本是单基因差异还是二基因差异,F_1和F_2代的芥酸含量都接近中亲值,F_1略大于中亲值和F_(20)世代均值分析表明,芥酸含量的遗传符合加性显性模型,加性效应占绝对优势,显性效应不显著。用数量遗传学方法估计的芥酸基因数与已知的结果相近。     

昆虫口腔分泌物效应子及其在害虫防治中基于RNAi技术的应用展望

昆虫口腔分泌物(oral secretion, OS),又称返吐液,是昆虫唾液腺分泌的唾液和肠道分泌物的混合液。昆虫取食寄主植物过程中,OS随之分泌至植物中,并影响植物的防御反应。RNA干扰(RNAinterference, RNAi)是研究昆虫基因功能有价值的反向遗传学工具,也是目前最有可能应用于害虫防治的新技术。本文主要综述了昆虫OS对寄主植物防御的影响、昆虫OS效应子的鉴定和OS效应子基于RNAi技术在害虫防治中可行性及应用前景。昆虫OS对寄主植物防御的影响主要表现为干扰植物的茉莉酸信号通路、筛管阻塞、Ca²⁺通路等防御反应,进而促进昆虫摄取食物。目前,昆虫OS效应子主要鉴定手段是通过昆虫唾液腺转录组分析和OS蛋白组分析;而已鉴定的OS效应子主要来源于刺吸式口器昆虫,在咀嚼式口器昆虫中的报道甚少;功能研究发现昆虫OS效应子在寄主植物中的表达会影响昆虫存活率、繁殖力和取食能力及昆虫和植物的其他重要生理指标,并通过鉴定OS效应子与植物防御机制的相互作用关系,进而证明OS效应子在昆虫与寄主植物关系中的重要性。基于RNAi技术,通过注射、饲喂和植物介导RNAi等方法在多种昆虫中产生了OS效应子基因下调和生长发育受影响的现象,由此说明OS效应子基因已具备作为RNAi靶标的条件。虽然目前研究尚处于实验室阶段,但已证明其应用于害虫防治方面具有一定的可行性。昆虫口腔分泌物是研究昆虫与寄主植物相互作用机制的新方向。最后,对OS未来潜在的研究方向进行了展望,以期对我国害虫防治的研究提供理论指导。     

利用cDNA微阵列-CGH筛选支气管上皮细胞恶性转化中的扩增基因

目的:基因组不稳定是导致肺癌发生与发展的重要分子机理之一。本研究旨在筛选支气管上皮细胞恶性转化过程中拷贝数扩增的基因。方法:利用业已建立的支气管上皮细胞体外恶性转化模型,通过cDNA微阵列-CGH技术对支气管上皮来源的永生化细胞和癌变细胞的基因拷贝数进行了检测,并对部分结果进行了实时PCR验证。结果:永生化BEP2D细胞染色体中的某些区域存在不同程度的扩增,包括5q31.3、9q32-33.1、14q22.2-23.1、19p13.12-13.13、20q13.12-13.31;恶性转化BERP35T2细胞染色体中的扩增区域集中在1p12-13.1、5q33.1、5q31.3、9q32、19p13.12-13.13;5q31.3、9q32、19q13.12-13.13是以上2种细胞系中的共同扩增区域。共检测到201个基因的拷贝数发生扩增,其中PCNA、TP53及GADD45A基因的异常扩增已经实时PCR进一步验证。结论:在支气管上皮细胞恶性转化过程中,病毒与低剂量辐射的双重作用使得某些重要基因的拷贝数发生扩增,因基因剂量增加而导致某些癌基因高表达可能是细胞恶性转化的重要机制之一。