The arms race between Magnaporthe oryzae and rice: Diversity and interaction of Avr and R genes

Rice blast disease, caused by Magnaporthe oryzae, threatens global food security. The rice blast pathosystem is a longstanding model system for understanding plant-microbe interactions. In order to elucidate the coevolution of the host and pathogen, and provide the appropriate methods for preventing or controlling rice blast disease, researchers have focused on the evolution of virulence factors and resistance genes. Thus far, more than 30 rice blast resistance(R) genes and 12 avirulence(Avr) genes have been cloned. This review summarizes the cloned rice blast R genes, cloned Avr genes of M. oryzae and the interaction between them. This discussion also considers some of the major unanswered questions concerning this pathosystem and the opportunities for future investigations.     

海洋动物核糖体RNA基因的结构特征和功能进化

核糖体普遍存在于各种细胞中,由大小两个亚基组成,是细胞中进行合成蛋白质的场所。核糖体组成成分为核糖体RNA以及蛋白质。核糖体RNA基因被广泛应用于海洋动物研究中,本文着重介绍海洋动物核糖体RNA基因的结构特征以及功能进化,供生物进化、分子系统学、系统发育以及海洋动物分类和种质鉴定等研究者参考。     

植物无选择标记转基因技术的研究进展

在植物基因转移过程中,标记基因常被用于筛选转化细胞或组织,给转基因工作带来很大方便.但在获得转基因植物之后,筛选标记基因的表达往往对环境及植物体的生长发育产生不良影响,且不利于使用相同标记基因进行多重转化.因此,使转基因植物释放后不带选择标记基因,对从事转基因的工作人员及消费者来说都是极为重要的.本文在对几种去除标记基因的方法进行总结的基础上,对该技术未来的发展趋势进行了展望.     

Synthetic biology: integrated gene circuits

A major goal of synthetic biology is to develop a deeper understanding of biological design principles from the bottom up, by building circuits and studying their behavior in cells. Investigators initially sought to design circuits "from scratch" that functioned as independently as possible from the underlying cellular system. More recently, researchers have begun to develop a new generation of synthetic circuits that integrate more closely with endogenous cellular processes. These approaches are providing fundamental insights into the regulatory architecture, dynamics, and evolution of genetic circuits and enabling new levels of control across diverse biological systems.     

Plant research. Can genetically modified crops go 'greener'?

A flood of new information from projects such as the sequencing of the genome of the mustard plant Arabidopsis has pinpointed genes involved in key processes such as speeding up flowering, changing a plant's basic architecture, or improving pest resistance. One example appears on page 344 of this issue; researchers report the cloning of an Arabidopsis gene called FRIGIDA and show that natural mutations leading to loss of FRIGIDA function are associated with early flowering, a helpful adaptation in some cold climates. Such work could allow researchers to enhance the traits they want by introducing one or a few genes from another plant, or by modifying the regulation of genes in their original settings.     

水稻花发育研究进展

迄今为止,双子叶植物花发育模型研究已基本成熟,这些模型在一定程度上也适用于水稻等单子叶植物的研究.目前,已鉴定克隆了部分与水稻花发育相关的基因,如水稻稀穗LAX、PLAI、LHD、FZP、CL、RFL、RAP1A和RAP1B基因以及花器官发育的水稻ABCDE 5类功能基因和花序变异基因包括Lax、Fzp、OsCKX2、Fon1等,促进了人们对水稻花发育机制的进一步了解.但是有关水稻花发育特异基因之间的调控及作用机理尚未清楚,今后需采用以先进的生物技术为手段,通过分离、鉴定更多的水稻花发育突变体基因,深入探讨各个基因的功能及相互作用,最终系统了解水稻花发育调控机理,从而为深人研究单子叶花序发育奠定基础.     

中国莲性状进化趋势分析

中国莲包含藕莲、子莲和花莲3种类型,是中国药食两用、具观赏、栽培面积大、品种资源丰富的水生经济作物。尽管已对其进行了基因组测序和相关基因筛选、克隆,但对性状的进化趋势还不了解,难以为育种者和基因改良者提供目标和方向。依据大量样本观测数据对中国莲的单一性状、性状互作进行分析推理,同时以多酚氧化酶活性在藕莲地下茎不同藕段部位的分布式样阐释该酶对藕莲抗病虫害性状进化的影响,并依据分析结果提出后续各类新品种选育亲本的选择建议。依据中国莲19个生物学性状对其进化趋势进行详细分析,旨在为同行提供参考。     

水稻披叶突变体的研究进展

水稻披叶突变体最初来源于国际水稻研究所(IRRI)的RGS20及其衍生系,后来又有其他的披叶突变体被发现,该性状受单隐性基因或多隐性基因控制。披叶突变体可作为新的种质资源来加以研发,已选育出的具有披叶性状的不育系,在繁殖、制种过程中能有效降低成本,节约时间,提高制种产量和种子纯度。水稻披叶性状的遗传和基因定位分析正在进行。     

Genomics. Painting a picture of genome evolution

A new analysis of the genome sequences of two bacteria shows that genes can be lost as well as gained during evolution. Even more intriguingly, the work provides snapshots capturing gene decay in the act and thus illuminates the actual genomic changes that occurred over tens of millions of years of evolution. The research, which is described on page 2093, focuses on two pathogenic bacteria: Rickettsia conorii, the culprit in Mediterranean spotted fever, and R. prowazekii, which causes typhus.     

The snarls and sneers that keep violence at bay

The ability to mete out violence appears to be linked to survival in the animal kingdom. But a handful of researchers is now making a persuasive case that scores are settled far more often by subtle, nonviolent signals such as a curled lip or a snarl. Their provocative idea is that inflicting violence on a member of one's own species is a pathological condition that arises when these signals are missed or misinterpreted.     

Genetic Evolution Analysis on Wild Isolates of Citrus Tristeza Virus Originated in China Based on Coat Protein Genes Sequences

The coat protein （CP） genes were cloned and sequenced from viral particles of 11 isolates of citrus tristeza virus （CTV） collected from wild citrus plants in China and 4 Chinese isolates from cultivated sweet orange and pummelo varieties, respectively. By analyzing and comparing the nucleotide and amino acid sequences of CP genes, the 11 wild CTV isolates were found over 92% identical with 4 Chinese CTV isolates and 21 exotic CTV isolates from cultivated citrus. From 91 to 100% of the CTV CP gene sequences in wild type citrus plants were generally well conserved. Genetic evolution analysis indicated that the GC% of the CP gene was less than AT%, and more transition were found in the CP genes than transversion with the transition/transversion ratio ranging from 6.3 to 7.0 among species. The substitution frequency was the highest at the third codon, followed by the first and second codon. The ratio of non-synonymous mutations （du） to synonymous mutations （ds） was far lower than 1, suggesting that the CP gene might have experienced purifying selection in the evolution. Phylogenetic analysis revealed that the 11 CTV isolates in Chinese wild type citrus belonged to different phylogenetic clusters, and shared higher homology and closer relationships with other cultivated citrus CTV isolates from different countries, which indicated complicated genetic relationships among the CTV isolates. In addition, CTV isolates with similar biological characteristics usually located into the same clusters. Therefore, the conclusion was drawn that pathogenicity was critical to evolution and origin of CTV.     

Tumor angiogenesis. Gene expression patterns identified

Researchers have obtained the most detailed sketch yet of how cancerous tumors secure the blood supplies that nourish their growth. On page 1197, a team reports the results of a large-scale comparison of the genes expressed in the blood vessels of human colon cancers and of normal colon tissue. They've found that the gene expression patterns of the two types of vasculature are distinctly different. The findings could help researchers develop new anticancer drugs that work by homing in on the protein products of genes that are overexpressed in tumor vessels, thus shutting off the growth of blood vessels the tumor needs to survive.     

Evolutionary biology. Chewed leaves reveal ancient relationship

On page 291, researchers describe a new beetle fossil based not on traces of the insect skeleton but on the distinctive gouges the beetles left when they munched on 11 ginger leaves many millions of years ago. The chew marks of the newly described Cephaloleichnites strongi prove that leaf beetles underwent rapid evolution and diversification more than 65 million years ago, possibly taking advantage of (and perhaps influencing) the rapid diversification among flowering plants occurring at the same time. What's more, C. strongi represents the earliest known rolled-leaf beetle species, hundreds of which today still prefer just one of the ginger- and heliconia-like plants in the Zingiberales order.     

The evolution of resistance gene in plants

Resistance genes enable plants to fight against plant pathogens. Plant resistance genes (R gene) are organized complexly in genome. Some resistance gene sequence data enable an insight into R gene structure and gene evolution. Some sites like Leucine-Rich Repeat (LRR) are of specific interest since homologous recombination can happen. Crossing over, transposon insertion and excision and mutation can produce new specificity. Three models explaining R gene evolution were discussed. More information needed for dissection of R gene evolution though some step can be inferred from genetic and sequence analysis.     

Parallel patterns of evolution in the genomes and transcriptomes of humans and chimpanzees

The determination of the chimpanzee genome sequence provides a means to study both structural and functional aspects of the evolution of the human genome. Here we compare humans and chimpanzees with respect to differences in expression levels and protein-coding sequences for genes active in brain, heart, liver, kidney, and testis. We find that the patterns of differences in gene expression and gene sequences are markedly similar. In particular, there is a gradation of selective constraints among the tissues so that the brain shows the least differences between the species whereas liver shows the most. Furthermore, expression levels as well as amino acid sequences of genes active in more tissues have diverged less between the species than have genes active in fewer tissues. In general, these patterns are consistent with a model of neutral evolution with negative selection. However, for X-chromosomal genes expressed in testis, patterns suggestive of positive selection on sequence changes as well as expression changes are seen. Furthermore, although genes expressed in the brain have changed less than have genes expressed in other tissues, in agreement with previous work we find that genes active in brain have accumulated more changes on the human than on the chimpanzee lineage.     

New genes in Drosophila quickly become essential

To investigate the origin and evolution of essential genes, we identified and phenotyped 195 young protein-coding genes, which originated 3 to 35 million years ago in Drosophila. Knocking down expression with RNA interference showed that 30% of newly arisen genes are essential for viability. The proportion of genes that are essential is similar in every evolutionary age group that we examined. Under constitutive silencing of these young essential genes, lethality was high in the pupal stage and also found in the larval stages. Lethality was attributed to diverse cellular and developmental defects, such as organ formation and patterning defects. These data suggest that new genes frequently and rapidly evolve essential functions and participate in development.     

Medicine. DNA arrays reveal cancer in its many forms

The use of microarrays--slides or chips systematically dotted with DNA from thousands of genes--to determine gene expression patterns is providing a wealth of new information that should aid in cancer diagnosis and ultimately in therapy. In the past several months, researchers in several labs have used microarray technology to identify specific subtypes of a variety of cancers, including leukemias and lymphomas, the dangerous skin cancer melanoma, and breast cancer. In some cases, they can determine which cancers are likely to respond to current therapies and which aren't. In addition, the studies are giving researchers a fix on which genes are important for the development, maintenance, and spread of the various cancers, and are thus possible drug targets.