水稻广谱抗稻瘟病基因研究进展

稻瘟病是水稻生产中的最严重病害之一,由于稻瘟菌小种的高度变异性,垂直抗性基因难以持续控制稻瘟病的危害,因此,克隆和利用广谱持久抗瘟基因被认为是解决稻瘟病问题最经济有效的策略。本文从广谱抗源的筛选与利用,广谱抗瘟基因的定位、克隆与应用等方面对水稻广谱抗稻瘟病基因研究取得的进展进行了概述,并介绍了广谱抗性分子机理的最新研究进展。基于国内外稻瘟病抗性基因研究的现状及趋势,以及我国丰富的抗瘟水稻种质资源,克隆越来越多的广谱抗瘟基因具有重要的理论与应用价值。     

Quantitative disease resistance to the bacterial pathogen Xanthomonas campestris involves an Arabidopsis immune receptor pair and a gene of unknown function

Although quantitative disease resistance (QDR) is a durable and broad‐spectrum form of resistance in plants, the identification of the genes underlying QDR is still in its infancy. RKS1 (Resistance related KinaSe1) has been reported recently to confer QDR in Arabidopsis thaliana to most but not all races of the bacterial pathogen Xanthomonas campestris pv. campestris (Xcc). We therefore explored the genetic bases of QDR in A. thaliana to diverse races of X. campestris (Xc). A nested genome‐wide association mapping approach was used to finely map the genomic regions associated with QDR to Xcc12824 (race 2) and XccCFBP6943 (race 6). To identify the gene(s) implicated in QDR, insertional mutants (T‐DNA) were selected for the candidate genes and phenotyped in response to Xc. We identified two major QTLs that confer resistance specifically to Xcc12824 and XccCFBP6943. Although QDR to Xcc12824 is conferred by At5g22540 encoding for a protein of unknown function, QDR to XccCFBP6943 involves the well‐known immune receptor pair RRS1/RPS4. In addition to RKS1, this study reveals that three genes are involved in resistance to Xc with strikingly different ranges of specificity, suggesting that QDR to Xc involves a complex network integrating multiple response pathways triggered by distinct pathogen molecular determinants.     

Recognition and response in plant-pathogen interactions

Most plants are resistant to the majority of pathogens. Susceptibility is the exception to the more common state of resistance, i.e., being refractory to infection. However, plant pathogens cause serious economic losses by reducing crop yield and quality. Although such organisms are relatively simple genetic entities, in plants, the mechanisms underlying the generation of disease symptoms and resistance responses are complex and, often, unknown. The study of genes associated with plant-pathogen resistance addresses fundamental questions about the molecular, biochemical, cellular, and physiological means of these interactions. Over the past 10 years, the cloning and analysis of numerous plant resistance genes has led researchers to formulate unifying theories about resistance and susceptibility, and the co-evolution of plant pathogens and their hosts. In this review, we discuss the identification of response genes that have been characterized at the molecular level, as well as their putative links to various signaling pathways. We also summarize the knowledge regarding crosstalk among signaling pathways and plant resistance genes.     

Resistance to Gray Leaf Spot of Maize: Genetic Architecture and Mechanisms Elucidated through Nested Association Mapping and Near-Isogenic Line Analysis

Gray leaf spot (GLS), caused by Cercospora zeae-maydis and Cercospora zeina, is one of the most important diseases of maize worldwide. The pathogen has a necrotrophic lifestyle and no major genes are known for GLS. Quantitative resistance, although poorly understood, is important for GLS management. We used genetic mapping to refine understanding of the genetic architecture of GLS resistance and to develop hypotheses regarding the mechanisms underlying quantitative disease resistance (QDR) loci. Nested association mapping (NAM) was used to identify 16 quantitative trait loci (QTL) for QDR to GLS, including seven novel QTL, each of which demonstrated allelic series with significant effects above and below the magnitude of the B73 reference allele. Alleles at three QTL, qGLS1.04, qGLS2.09, and qGLS4.05, conferred disease reductions of greater than 10%. Interactions between loci were detected for three pairs of loci, including an interaction between iqGLS4.05 and qGLS7.03. Near-isogenic lines (NILs) were developed to confirm and fine-map three of the 16 QTL, and to develop hypotheses regarding mechanisms of resistance. qGLS1.04 was fine-mapped from an interval of 27.0 Mb to two intervals of 6.5 Mb and 5.2 Mb, consistent with the hypothesis that multiple genes underlie highly significant QTL identified by NAM. qGLS2.09, which was also associated with maturity (days to anthesis) and with resistance to southern leaf blight, was narrowed to a 4-Mb interval. The distance between major leaf veins was strongly associated with resistance to GLS at qGLS4.05. NILs for qGLS1.04 were treated with the C. zeae-maydis toxin cercosporin to test the role of host-specific toxin in QDR. Cercosporin exposure increased expression of a putative flavin-monooxygenase (FMO) gene, a candidate detoxification-related gene underlying qGLS1.04. This integrated approach to confirming QTL and characterizing the potential underlying mechanisms advances the understanding of QDR and will facilitate the development of resistant varieties.     

昆虫抗药性分子机制研究的新进展

昆虫抗性机制的研究对于抗性监测、治理及新农药的研制具有重要意义。在过去几十年中,人们对与昆虫杀虫剂抗性有关的昆虫行为、生理代谢活动以及作用靶标等进行了广泛的研究。已经证实,昆虫的抗药性与行为改变、生理功能改变、解毒功能增强以及靶标不敏感性有关。近年来,随着分子生物学以及昆虫基因组学的发展,昆虫抗药性的分子机理有了突破性进展,已发现并克隆了一些靶标基因,与抗药性相关的基因突变也得到广泛验证。本文综述了昆虫的抗药性机理在分子生物学上的研究最新进展,重点阐述了与昆虫抗性相关基因的扩增、表达及基因结构的改变等相关内容。     

昆虫钠通道的结构和与击倒抗性有关的基因突变

击倒抗性(kdr)是指昆虫和其他节肢动物由于它们的神经系统对DDT和拟除虫菊酯类杀虫剂的敏感性降低而引起的抗性。电压敏感的钠通道是DDT和拟除虫菊酯类杀虫剂的主要靶标。已知拟除虫菊酯是通过改变位于神经膜上的这类通道而发挥其杀虫效果的,钠通道基因的点突变是产生kdr抗性的主要原因。40年来kdr抗性一直是重要的研究课题,但近10年来在kdr分子生物学方面取得了很大进展。本文主要综述了1996年以来所取得的新进展,着重于钠通道的结构、在14种害虫中与kdr抗性相关的钠通道基因突变及其氨基酸序列的多态性。这些结果有助于对拟除虫菊酯改变钠通道的功能及其机理作进一步探究。     

A novel knowledge-driven systems biology approach for phenotype prediction upon genetic intervention

Deciphering the biological networks underlying complex phenotypic traits, e.g., human disease is undoubtedly crucial to understand the underlying molecular mechanisms and to develop effective therapeutics. Due to the network complexity and the relatively small number of available experiments, data-driven modeling is a great challenge for deducing the functions of genes/proteins in the network and in phenotype formation. We propose a novel knowledge-driven systems biology method that utilizes qualitative knowledge to construct a Dynamic Bayesian network (DBN) to represent the biological network underlying a specific phenotype. Edges in this network depict physical interactions between genes and/or proteins. A qualitative knowledge model first translates typical molecular interactions into constraints when resolving the DBN structure and parameters. Therefore, the uncertainty of the network is restricted to a subset of models which are consistent with the qualitative knowledge. All models satisfying the constraints are considered as candidates for the underlying network. These consistent models are used to perform quantitative inference. By in silico inference, we can predict phenotypic traits upon genetic interventions and perturbing in the network. We applied our method to analyze the puzzling mechanism of breast cancer cell proliferation network and we accurately predicted cancer cell growth rate upon manipulating (anti)cancerous marker genes/proteins.     

Genes of multidrug resistance in haematological malignancies

Since the early 1970s, multiple drug resistance has been known to exist in cancer cells and is thought to be attributable to a membrane-bound, energy-dependent pump protein (P-glycoprotein [P-gp]) capable of extruding various related and unrelated chemotherapeutic drugs. The development of refractory disease in haematological malignancies is frequently associated with the expression of one or several multidrug resistance (MDR) genes. MDR1, multidrug resistance-associated protein (MRP) and lung-resistance protein (LRP) have been identified as important adverse prognostic factors. Recently it has become possible to reverse clinical MDR by blocking P-gp-mediated drug efflux. The potential relevance of these reversal agents of MDR as well as the potential new approaches to treat the refractory disease are discussed in this article. In addition, an array of different molecules and mechanisms by which resistant cells can escape the cytotoxic effect of anticancer drugs has now been identified. These molecules and mechanisms include apoptosis-related proteins and drug inactivation enzymes. Resistance to chemotherapy is believed to cause treatment failure in more than 50% patients. Clearly, if drug resistance could be overcome, the impact on survival would be highly significant. This review focuses on molecular mechanism of drug resistance in haematological malignancies with emphasis on molecules involved in MDR. In addition, it brings the survey of methods involved in determination of MDR, in particular P-gp/MDR1, MRP and LRP.     

Molecular genetics of disease resistance in cereals

AIMS: This Botanical Briefing attempts to summarize what is currently known about the molecular bases of disease resistance in cereal species and suggests future research directions. SCOPE: An increasing number of resistance (R) genes have been isolated from rice, maize, wheat and barley that encode both structurally related and unique proteins. This R protein diversity may be attributable to the different modus operandi employed by pathogen species in some cases, but it is also a consequence of multiple defence strategies being employed against phytopathogens. Mutational analysis of barley has identified additional genes required for activation of an R gene-mediated defence response upon pathogen infection. In some instances very closely related barley R proteins require different proteins for defence activation, demonstrating that, within a single plant species, multiple resistance signalling pathways and different resistance strategies have evolved to confer protection against a single pathogen species. Despite the apparent diversity of cereal resistance mechanisms, some of the additional molecules required for R protein function are conserved amongst cereal and dicotyledonous species and even other eukaryotic species. Thus the derivation of functional homologues and interacting partner proteins from other species is contributing to the understanding of resistance signalling in cereals. The potential and limit of utilizing the rice genome sequence for further R gene isolation from cereal species is also considered, as are the new biotechnological possibilities for disease control arising from R gene isolation. CONCLUSIONS: Molecular analyses in cereals have further highlighted the complexity of plant-pathogen co-evolution and have shown that numerous active and passive defence strategies are employed by plants against phytopathogens. Many advances in understanding the molecular basis of disease resistance in cereals have focused on monogenic resistance traits. Future research targets are likely to include less experimentally tractable, durable polygenic resistances and nonhost resistance mechanisms.     

防御素的生物学特性及其抗病基因工程

防御素是一种富含半胱氨酸的小分子多肽,对细菌等微生物具有广谱抗性,且作用机制特殊。迄今为止,国内外在防御素方面进行了大量的研究,已经从各类生物体中分离出不同种类的防御素,并在基因工程和医药领域呈现广泛的应用前景。文章对防御素的分类、生物学特性,包括哺乳动物α-、β-、θ-防御素、昆虫以及植物防御素的分子结构及抗菌活性进行了综述,阐述了防御素的膜作用及与细胞内复合物结合的作用机制。总结和归纳了防御素基因的分离、表达研究进展及动、植物防御素基因在抗病基因工程领域的应用,并对防御素在未来的生物制药和植物抗病基因工程方面的应用前景进行了展望。     

Systematic Analysis and Comparison of Nucleotide-Binding Site Disease Resistance Genes in a Diploid Cotton Gossypium raimondii

Plant disease resistance genes are a key component of defending plants from a range of pathogens. The majority of these resistance genes belong to the super-family that harbors a Nucleotide-binding site (NBS). A number of studies have focused on NBS-encoding genes in disease resistant breeding programs for diverse plants. However, little information has been reported with an emphasis on systematic analysis and comparison of NBS-encoding genes in cotton. To fill this gap of knowledge, in this study, we identified and investigated the NBS-encoding resistance genes in cotton using the whole genome sequence information of Gossypium raimondii. Totally, 355 NBS-encoding resistance genes were identified. Analyses of the conserved motifs and structural diversity showed that the most two distinct features for these genes are the high proportion of non-regular NBS genes and the high diversity of N-termini domains. Analyses of the physical locations and duplications of NBS-encoding genes showed that gene duplication of disease resistance genes could play an important role in cotton by leading to an increase in the functional diversity of the cotton NBS-encoding genes. Analyses of phylogenetic comparisons indicated that, in cotton, the NBS-encoding genes with TIR domain not only have their own evolution pattern different from those of genes without TIR domain, but also have their own species-specific pattern that differs from those of TIR genes in other plants. Analyses of the correlation between disease resistance QTL and NBS-encoding resistance genes showed that there could be more than half of the disease resistance QTL associated to the NBS-encoding genes in cotton, which agrees with previous studies establishing that more than half of plant resistance genes are NBS-encoding genes.     

Tracking disease resistance deployment in potato breeding by enrichment sequencing

Following the molecular characterisation of functional disease resistance genes in recent years, methods to track and verify the integrity of multiple genes in varieties are needed for crop improvement through resistance stacking. Diagnostic resistance gene enrichment sequencing (dRenSeq) enables the high‐confidence identification and complete sequence validation of known functional resistance genes in crops. As demonstrated for tetraploid potato varieties, the methodology is more robust and cost‐effective in monitoring resistances than whole‐genome sequencing and can be used to appraise (trans) gene integrity efficiently. All currently known NB‐LRRs effective against viruses, nematodes and the late blight pathogen Phytophthora infestans can be tracked with dRenSeq in potato and hitherto unknown polymorphisms have been identified. The methodology provides a means to improve the speed and efficiency of future disease resistance breeding in crops by directing parental and progeny selection towards effective combinations of resistance genes.     

白念珠菌唑类药物耐药相关转录因子研究进展

近年来白念珠菌的感染率呈逐年上升趋势,随着唑类药物的广泛应用,耐药菌株不断增多,已成为临床治疗的一大难题.白念珠菌的耐药机制主要与ERG 11基因的突变和过表达、药物外排泵相关基因表达增多及生物膜的形成等有关,由于转录因子是耐药基因表达的关键调节因子,关于锌簇转录因子与耐药关系的研究越来越多,如TAC 1、MRR 1、MRR 2、UPC 2、NDT 80等,其点突变可引起某些耐药基因的过表达而介导耐药,该领域研究已成为热点,该文就此研究进展做一概述.     

Genetic and molecular analysis of tomato Cf genes for resistance to Cladosporium fulvum.

In many plant-pathogen interactions resistance to disease is controlled by the interaction of plant-encoded resistance (R) genes and pathogen-encoded avirulence (Avr) genes. The interaction between tomato and the leaf mould pathogen Cladosporium fulvum is an ideal system to study the molecular basis of pathogen perception by plants. A total of four tomato genes for resistance to C. fulvum (Cf-2, Cf-4, Cf-5 and Cf-9) have been isolated from two genetically complex chromosomal loci. Their gene products recognize specific C. fulvum-encoded avirulence gene products (Avr2, Avr4, Avr5 and Avr9) by an unknown molecular mechanism. Cf genes encode extracellular membrane-anchored glycoproteins comprised predominantly of 24 amino acid leucine-rich repeats (LRRs). Cf genes from the same locus encode proteins which are more than 90% identical. Most of the amino-acid sequence differences correspond to the solvent-exposed residues within a beta-strand/beta-turn structural motif which is highly conserved in LRR proteins. Sequence variability within this motif is predicted to affect the specificity of ligand binding. Our analysis of Cf gene loci at the molecular level has shown they comprise tandemly duplicated homologous genes, and suggests a molecular mechanism for the generation of sequence diversity at these loci. Our analysis provides further insight into the molecular basis of pathogen perception by plants and the organization and evolution of R gene loci.     

The yeast multidrug transporter Qdr3 (Ybr043c): localization and role as a determinant of resistance to quinidine, barban, cisplatin, and bleomycin

Saccharomyces cerevisiae ORF YBR043c, predicted to code for a transporter of the major facilitator superfamily required for multiple drug resistance, encodes a plasma membrane protein that confers resistance to quinidine and barban, as observed before for its close homologues QDR1 and QDR2. This ORF was, thus, named the QDR3 gene. The increased expression of QDR3, or QDR2, also leads to increased resistance to the anticancer agents cisplatin and bleomycin. However, no evidence for increased QDR3 expression in yeast cells exposed to all these inhibitory compounds was found. Transport assays support the concept that Qdr3 is involved, even if opportunistically, in the active export of quinidine out of yeast cell. A correlation was established between the efficiency of quinidine active export mediated by Qdr3p, Qdr2p or Qdr1p, and the efficacy of the expression of the encoding genes in alleviating the deleterious action of quinidine, as well as of the other compounds (QDR2>QDR3>QDR1).