Genome sequence of the ultrasmall unicellular red alga Cyanidioschyzon merolae 10D

Small, compact genomes of ultrasmall unicellular algae provide information on the basic and essential genes that support the lives of photosynthetic eukaryotes, including higher plants. Here we report the 16,520,305-base-pair sequence of the 20 chromosomes of the unicellular red alga Cyanidioschyzon merolae 10D as the first complete algal genome. We identified 5,331 genes in total, of which at least 86.3% were expressed. Unique characteristics of this genomic structure include: a lack of introns in all but 26 genes; only three copies of ribosomal DNA units that maintain the nucleolus; and two dynamin genes that are involved only in the division of mitochondria and plastids. The conserved mosaic origin of Calvin cycle enzymes in this red alga and in green plants supports the hypothesis of the existence of single primary plastid endosymbiosis. The lack of a myosin gene, in addition to the unexpressed actin gene, suggests a simpler system of cytokinesis. These results indicate that the C. merolae genome provides a model system with a simple gene composition for studying the origin, evolution and fundamental mechanisms of eukaryotic cells.     

Evolutionary transfer of the chloroplast tufA gene to the nucleus

Evolutionary gene transfer is a basic corollary of the now widely accepted endosymbiotic theory, which proposes that mitochondria and chloroplasts originated from once free-living eubacteria. The small organellar chromosomes are remnants of larger bacterial genomes, with most endosymbiont genes having been either transferred to the nucleus soon after endosymbiosis or lost entirely, with some being functionally replaced by pre-existing nuclear genes. Several lines of evidence indicate that relocation of some organelle genes could have been more recent. These include the abundance of non-functional organelle sequences of recent origin in nuclear DNA, successful artificial transfer of functional organelle genes to the nucleus, and several examples of recently lost organelle genes, although none of these is known to have been replaced by a nuclear homologue that is clearly of organellar ancestry. We present gene sequence and molecular phylogenetic evidence for the transfer of the chloroplast tufA gene to the nucleus in the green algal ancestor of land plants.     

The gain of two chloroplast tRNA introns marks the green algal ancestors of land plants

The relationship of green algae to land plants has greatly interested botanists for more than a century. In recent years, several characters, particularly ultrastructural ones, have been used to define a green algal group (Charophyceae) from which land plants are thought to have arisen. Here we provide the first molecular genetic evidence in support of the charophycean origin of land plants. Group II introns have previously been found in both the tRNAAla and tRNAIle genes of all land plant chloroplast DNAs examined, whereas all algae and eubacteria examined have uninterrupted genes. The distribution of these introns in Coleochaete, Nitella and Spirogyra, members of the Charophyceae, confirms that these taxa are part of the lineage that gave rise to land plants. Furthermore, the intron data place Coleochaete and Nitella closer to land plants than Spirogyra. These introns were most probably acquired by the chloroplast genome more than 400-500 million years ago, the time of land plant origin.     

Bioinformatic analysis of expressed sequence tags from sporophyte of Porphyra yezoensis （Bagiaceae, Rhodophyta）

A total of 719 expressed sequence tags (EST) clustered into 329 non?redundant EST groups are obtained from the sporophyte cDNA library of red algae, Porphyra yezoensis. Gene Ontology (GO) analysis is employed in characterizing 60 strictest annotated unique genes out of the 329 EST groups and some domains such as COX1, Sod-Fe-C, GST-N, SHMT, and RNase-PH related to the enzymes and proteins functioning in cells have been identified by HMMPFAM search. As its leafy gametophyte, the similar codon usage with strong bias is found in P. yezoensis filamentous sporophyte, regardless of some differences found in given amino acids. The average GC content of the 329 unique genes is 53.0%. In contrast, the third nucleotide of codon exhibits a higher GC content (72%) than that of the first (58%) and the second (42%) nucleotides. Similarity search of the present study shows a novel EST ratio of 60.2%, which is against the Porphyra ESTs database, suggesting further investigations towards elucidating the characteristics of Porphyra functional genome.     

福建部分海藻凝集素的检测

用天然和经酶修饰的绵羊、兔、鸡，以及人的Ａ型、Ｂ型、ＡＢ型和Ｏ型７种红细胞，对产于福建的１６种海藻（绿藻１种、红藻８种、褐藻７种）进行了凝集素的检测．实验结果表明，每种海藻提取液至少能凝集２种以上天然或经酶修饰的红细胞。在检测的１６种海藻中，褐藻门的铁钉菜、厚网藻和绿藻门的浒苔产生的阳性凝血结果最广泛，能凝集供试的７种天然或经酶修饰的红细胞．红藻门的粗枝软骨藻、褐藻门的扁铁钉、鼠尾藻的凝血能力最差，只能凝集２或３种天然或经酶修饰的红细胞。在７种红细胞中，绵羊血红细胞对海藻凝集素最敏感。各种类型的红细胞经酶（胰蛋白酶）修饰后，对凝集素的敏感性普遍增加（鸡红细胞对几种海藻例外）。     

Nitrogen transfer in the arbuscular mycorrhizal symbiosis

Most land plants are symbiotic with arbuscular mycorrhizal fungi (AMF), which take up mineral nutrients from the soil and exchange them with plants for photosynthetically fixed carbon. This exchange is a significant factor in global nutrient cycles as well as in the ecology, evolution and physiology of plants. Despite its importance as a nutrient, very little is known about how AMF take up nitrogen and transfer it to their host plants. Here we report the results of stable isotope labelling experiments showing that inorganic nitrogen taken up by the fungus outside the roots is incorporated into amino acids, translocated from the extraradical to the intraradical mycelium as arginine, but transferred to the plant without carbon. Consistent with this mechanism, the genes of primary nitrogen assimilation are preferentially expressed in the extraradical tissues, whereas genes associated with arginine breakdown are more highly expressed in the intraradical mycelium. Strong changes in the expression of these genes in response to nitrogen availability and form also support the operation of this novel metabolic pathway in the arbuscular mycorrhizal symbiosis.     

刺玫果中氨基酸组成及含量的测定

本文测定了刺玫果中的氨基酸组成及含量，并与同科植物进行了比较。实验表明，该果实中氨基酸组成齐全、含量高；E／E＋N为对照样品的2—3倍。因此是一种很有价值的绿色植物。     

尖峰岭次生林和原始林林下灌木叶氨基酸对氮添加的响应

为了深入地了解热带山地雨林原始林与次生林叶氨基酸对氮添加的响应和适应机制, 以海南尖峰岭热带山地雨林原始林和次生林的林下常见植物为研究对象, 通过设置对照CK (0 kg N/(ha·a))、中氮添加M (50 kg N/(ha·a))和高氮添加H (100 kg N/(ha·a)) 3种氮添加处理的实验, 探究氮添加对林下灌木叶片氨基酸含量的影响。实验结果表明, 无氮添加时, 原始林与次生林的总氨基酸含量和水解氨基酸含量无显著差异, 原始林游离氨基酸总含量显著高于次生林; 中氮添加时, 次生林林下灌木叶氨基酸含量的响应程度高于原始林; 高氮添加时, 次生林与原始林林下灌木水解氨基酸的响应程度无显著差异, 原始林林下灌木游离氨基酸的响应程度高于次生林。     

Molecular characterization of GmNHX2, a Na＋/H＋ antiporter gene homolog from soybean,and its heterolosous expression to improve salt tolerance in Arabidopsis

Na＋/H＋ antiporters have been well documented to enhance plant salt tolerance by regulating cellular ion homeostasis. Here, a putative Na＋/H＋ antiporter gene homolog GmNHX2 from soybean was cloned and predicted to encode a protein of 534 amino acids with 10 putative transmembrane domains. GmNHX2 was expressed in all soybean plant tissues but enriched in roots and its expression was induced by NaCI and polyethylene glycol （PEG） treatments. GmNHX2 exhibits greater sequence similarity with LeNHX2 and AtNHX6 than that of AtNHX1 and AtSOS1. Although phylogenetic analysis clustered GmNHX2 with organellar （tonoplast and vesicles） antiporters, the GmNHX2-EGFP （enhanced green fluorescent protein） fusion protein was possibly localized in the plasma membrane or organelle membrane of transgenic plant cells, Furthermore, transgenic Arabidopsis plants expressing GmNHX2 were more tolerant to high NaCl concentrations during germination and seedling stages when compared with wild-type plants. These results suggest that GmNHX2 is a membrane Na＋/H＋ antiporter and may function to regulate ion homeostasis under salt stress.     

Ancestral chloroplast genome in Mesostigma viride reveals an early branch of green plant evolution

Sequence comparisons suggest that all living green plants belong to one of two major phyla: Streptophyta (land plants and their closest green algal relatives, the charophytes); and Chlorophyta (the rest of green algae). Because no green algae are known that pre-date the Streptophyta/Chlorophyta split, and also because the earliest diverging green algae show considerable morphological variation, the nature of the unicellular flagellate ancestor of the two green plant phyla is unknown. Here we report that the flagellate Mesostigma viride belongs to the earliest diverging green plant lineage discovered to date. We have sequenced the entire chloroplast DNA (118,360 base pairs) of this green alga and have conducted phylogenetic analyses of sequences derived from this genome. Mesostigma represents a lineage that emerged before the divergence of the Streptophyta and Chlorophyta, a position that is supported by several features of its chloroplast DNA. The structure and gene organization of this genome indicate that chloroplast DNA architecture has been extremely well conserved in the line leading to land plants.     

The highly reduced genome of an enslaved algal nucleus

Chromophyte algae differ fundamentally from plants in possessing chloroplasts that contain chlorophyll c and that have a more complex bounding-membrane topology. Although chromophytes are known to be evolutionary chimaeras of a red alga and a non-photosynthetic host, which gave rise to their exceptional membrane complexity, their cell biology is poorly understood. Cryptomonads are the only chromophytes that still retain the enslaved red algal nucleus as a minute nucleomorph. Here we report complete sequences for all three nucleomorph chromosomes from the cryptomonad Guillardia theta. This tiny 551-kilobase eukaryotic genome is the most gene-dense known, with only 17 diminutive spliceosomal introns and 44 overlapping genes. Marked evolutionary compaction hundreds of millions of years ago eliminated nearly all the nucleomorph genes for metabolic functions, but left 30 for chloroplast-located proteins. To allow expression of these proteins, nucleomorphs retain hundreds of genetic-housekeeping genes. Nucleomorph DNA replication and periplastid protein synthesis require the import of many nuclear gene products across endoplasmic reticulum and periplastid membranes. The chromosomes have centromeres, but possibly only one loop domain, offering a means for studying eukaryotic chromosome replication, segregation and evolution.     

小反刍兽疫病毒融合蛋白基因的克隆、序列分析及表达

根据GenBank报道的小反刍兽疫病毒(PPRV)融合蛋白(F)基因序列,用特异性引物对PPRV疫苗株F蛋白基因进行了RT-PCR扩增,并将其克隆到pGEM-T载体中进行测序。结果表明:F基因ORF全长1641 bp,编码546个氨基酸;推导的氨基酸序列中第1~18位氨基酸构成信号肽序列,第488~510氨基酸为跨膜区。构建原核表达载体pETF1和pETF2,转化E.coliBL21(DE3),用IPTG诱导表达。SDS-PAGE和Western-blotting的分析结果表明,F1和F2基因在大肠杆菌中均获得了表达,且均具有良好的反应原性。用Ni-NTA试剂盒纯化F1和F2重组蛋白,为研发检测PPRV特异性抗体的诊断试剂奠定了基础。     

甜菊钙调蛋白基因的克隆及结构分析

钙调蛋白（Calmodulin）是生物细胞内一种重要的调控蛋白，通过其与靶酶的相互作用控制细胞正常的生长发育及细胞对外界环境变化的反应，我们从甜菊顶芽和花芽中提取总RNA，逆转录合成cDNA第一链，以此为模板，参考GenBank上已发表植物的钙调蛋白基因序列合成5′端和3′端引物，利用多聚酶链式反应（PCR）扩增并克隆得到了甜菊钙调蛋白基因的两个异型基因，序列分析表明，它们均由450个核苷酸组成，编码148个氨基酸，在核苷酸序列上与迄今已知的多种植物钙调蛋白均有很高的同源性，同源率在83％以上，编码的氨基酸序列同源性更同，同源率高达95％以上，这两个基因之间存在差异，其核苷酸序列同源率为85％，编码区的氨基酸序列的同源率为99％，仅在第122个氨基酸由ALA代替了VAL。     

The structure of a plant photosystem I supercomplex at 3.4 A resolution

All higher organisms on Earth receive energy directly or indirectly from oxygenic photosynthesis performed by plants, green algae and cyanobacteria. Photosystem I (PSI) is a supercomplex of a reaction centre and light-harvesting complexes. It generates the most negative redox potential in nature, and thus largely determines the global amount of enthalpy in living systems. We report the structure of plant PSI at 3.4 A resolution, revealing 17 protein subunits. PsaN was identified in the luminal side of the supercomplex, and most of the amino acids in the reaction centre were traced. The crystal structure of PSI provides a picture at near atomic detail of 11 out of 12 protein subunits of the reaction centre. At this level, 168 chlorophylls (65 assigned with orientations for Q(x) and Q(y) transition dipole moments), 2 phylloquinones, 3 Fe(4)S(4) clusters and 5 carotenoids are described. This structural information extends the understanding of the most efficient nano-photochemical machine in nature.     

红藻门仙菜科Ceramiaceae的分类现状与展望

仙菜科Ceramiaceae海藻作为红藻门中的一个重要类群,具有较高的研究价值.但由于科级以下分类系统、系统演化和物种数目在不同历史时期的变化比较大,仙菜科的分类研究还存在着许多争议.本文梳理目前国际与国内仙菜科分类学上的各种变动与争议,总结该科分类系统存在的问题,概述分子标记在仙菜科系统发育分析中存在的问题.同时,为...     

国际核能发展态势

石油和天然气价格的上涨,以及温室气体减排压力,使得核能利用备受关注。在欧美发达国家,核电站及其他核设施的相继退役,既给反对核能找到了借口,也给核能的发展提供了机遇——如果核废物能够适当处理的话。综述了国际核能利用的现状、特点,以及核能技术(包括第三代和第四代核能技术、核聚变技术、燃料循环技术等)的研究进展状况,展望了未来核能发展的态势及其对中国核能发展的启示。     

3个观赏海棠半同胞家系子代叶色动态分析与初选

【目的】探讨观赏海棠自由授粉子代苗期叶色变异规律,为半同胞家系育种及海棠新品种选育提供参考。【方法】以3个绿叶观赏海棠品种(‘冬金'、‘冬红'和‘红珠宝')为母本的自由授粉半同胞家系子代为试材,采用Minolta色差仪对120株半同胞家系子代不同叶位叶片色彩进行动态测定,进行叶色动态变化研究及优选。【结果】①基于5—8月子代上叶位L^*、C^*、h°色彩参数进行CIELCH色空间动态分布图的构建,发现 ‘冬金' 家系子代叶色参数位点最为分散,叶色最为丰富,子代中出现母本不具有的亮绿色和红色叶片。②基于5月子代上位叶色彩参数(L^*、C^*、h°),构建叶色聚类分析图,发现在欧式距离19水平上可将子代划分为两大色系类群和 5 个子色系类群,即绿色系(包括褐绿色、深绿色和亮绿色)和红色系(包括紫红色和棕红色),其中绿色系占比92.5%。③基于聚类分析结果及色彩参数分别构建绿色系和红色系子代评价体系,绿色系中从高亮度、高饱和度及色彩稳定性角度优选出 ‘冬金' 家系的‘A03'、‘A09', ‘冬红' 家系的‘D21'和 ‘红珠宝' 家系的‘C10'、‘C26'、‘C29', 红色系从低色调角和色彩持续性角度优选出‘冬金' 家系的‘A37',优株叶色观赏性优于资源圃品种。【结论】通过自由授粉,观赏海棠半同胞子代群体遗传基础大大增加,叶色多样性得以提高; 以参数色空间作为优选评价方法,更为直观可视化,可用作观赏海棠实践生产及新品种选育等。