Reactive oxygen species are involved in cell death in wheat roots against powdery mildew

Inoculation of wheat(Triticum aestivum L.) leaves with wheat powdery mildew fungus(Blumeria graminis f. sp. tritici) induces the cell death in adventitious roots. Reactive oxygen species(ROS) play a key role in respond to biotic stress in plants. To study the involvement of ROS and the degree of cell death in the wheat roots following inoculation, ROS levels and microstructure of root cells were analyzed in two wheat cultivars that are susceptible(Huamai 8) and resistant(Shenmai 8) to powdery mildew fungus. At 18 d after powdery mildew fungus inoculation, only Huamai 8 displayed the leaf lesions, while root cell death occurred in both varieties. Huamai 8 had a high level of ROS accumulation, which is associated with increased root cell degradation, while in Shenmai 8, there was little ROS accumulation correlating with slight root cell degradation. The molecular study about the expression levels of ROS scavenging genes(MnSOD and CAT) in wheat roots showed that these genes expression decreased after the leaves of wheat was inoculated. The difference between Huamai 8 and Shenmai 8 on subcellular localization of H2 O2 and O2–· was corresponded with the different down-regulation of the genes encoding for superoxide dismutase and catalase in two wheat cultivars. These results suggested that ROS were involved in the process by which powdery mildew fungus induced cell death in wheat roots.     

Polymorphism and association analysis of a drought-resistant gene TaLTP-s in wheat

Lipid transfer protein(LTP) is a kind of small molecular protein, which is named for its ability to transfer lipid between cell membranes. It has been proved that the protein is involved in the responding to abiotic stresses. In this study, Ta LTP-s, a genomic sequence of TaLTP was isolated from A genome of wheat(Triticum aestivum L). Sequencing analysis exhibited that there was no diversity in the coding region of Ta LTP-s, but seven single nucleotide polymorphisms(SNPs) and 1 bp insertion/deletion(In Del) were detected in the promoter regions of different wheat accessions. Nucleotide diversity(π) in the region was 0.00033, and linkage disequilibrium(LD) extended over almost the entire Ta LTP-s region in wheat. The d CAPS markers based on sequence variations in the promoter regions(SNP-207 and SNP-1696) were developed, and three haplotypes were identified based on those markers. Association analysis between the haplotypes and agronomic traits of natural population consisted of 262 accessions showed that three haplotypes of Ta LTP-s were significantly associated with plant height(PH). Among the three haplotypes, Hap III is considered as the superior haplotype for increasing plant height in the drought stress environments. The G variance at the position of 207 bp could be a superior allele that significantly increased number of spikes per plant(NSP). The functional marker of Ta LTP-s provide a tool for marker-assisted selection regarding to plant height and number of spikelet per plant in wheat.     

甘蔗茎尖细胞有丝分裂过程中微管骨架的变化（英文）

In order to understand the microtubule change of monocotyls stem-tip during mitosis,the arrangement,transformation of microtubule array and its relation with chromosome movement during mitosis were studied with freezing microtome,indirect immunofluorescence,DAPI staining and fluorescence microscopy.The results showed that nucleolus was intact when the cortical microtubules formed;cortical microtubules were changed into phramoplast microtubule bands at mitosis prophase.When phramoplast microtubule came into being,nuclear membrane was ruptured and chromosome was arranged at the position of cell plate;subsequently,phramoplast microtubules were changed into phragmoplast microtubules,phramoplast microtubules were shortening and microtubules on the sides of cell plate were increasing gradually,during this course sister chromatid was separated by microtubules at cell plate and tract to the two poles,forming phragmoplast microtubules.Then the nucleolus of two daughter cells formed and separated in the end with the increase of cells numbers.Therefore,cell division orientation could be judged from the arrangement of cell microtubules in different periods in order to understand its growth status.     

A Preliminary Study on Systems Engineering-Based Method for the Evaluation of Allelopathic Potential in Crops and Its Application

The objective of this study was to develop a method to assess and analyze the total allelopathic potential of crop germplasm and to test this method on four winter wheat accessions commonly planted in the Loess Plateau. A systems engineering model was developed and used to evaluate the total allelopathic potential of crop cultivars. In addition, a method for quantifying the total allelopathic potential in crop accessions was presented. Total allelopathic potential of four winter wheat accessions from the Loess Plateau was estimated and compared using a systems theory approach. The model assessed allelopathic potential in different parts of the plants from the time wheat turned green in spring until maturity. Results from these models indicated that the four wheat accessions had very weak allelopathic potential. Allelopathic potential declined in the order Xiaoyan 22 〉 Ningdong 1 〉 Fengchan 3 〉 Bima 1. This system engineering evaluation method allows for the assessment of allelopathic potential among crop varieties. It will help plant breeders to select and develop allelopathic crop accessions that combine weed suppression properties with agronomic traits related to yield and quality.     

Haplll of TaSAP1-A1, a Positively Selected Haplotype in Wheat Breeding

Stress-associated protein （SAP） has functions in maintaining plant cell elongation, embryo development and response to abiotic stresses. TaSAP1-A1, one of the Triticum aestivum SAP1 （TaSAP1） members located on wheat chromosome 7A was isolated for polymorphism analysis. HaplII of TaSAP1-A1 was found significantly associated with thousand-grain weight （TGW） in multiple environments. In this study, HaplII also made a positive contribution to TGW in Population 2. The distribution of TaSAP1-A1 HapIII was tracked among varieties released in different years and geographical environments of China. The frequency of HapIII showed an increasing trend during the breeding process in two different populations. The ItapIII was gradually selected and applied from 6.36% in landraces to 13.50% in modem varieties. These results exhibited that TaSAP1-A1 HapIII was positively selected during wheat breeding, which is beneficial for grain-yield improvement. The preferred HapIIl was initially selected and applied in the higher latitude areas of China in accord with the long day season and longer grain filling stage in these areas. Moreover, the frequency of HaplII in recent modem varieties was still quite low （19.29-26.67%）. It indicated a high application potential of TaSAP1-A 1 HapIII for improving grain yield in wheat breeding.     

Characterization of a TaJ Gene from Wheat

A novel J-domain protein gene was cloned from wheat （Triticum aestivum L.） using RT-PCR technology and named as TaJ. The J-domain protein is defined by the presence of a J-domain. The cDNA of T. aestivum gene, TaJ （GenBank accession number： DQ789026）, was 1263 bp and contained a complete open reading frame （ORF） encoding a J-domain protein of 420 amino acid residues. The predicted amino acid sequence of TaJ possesses three functionally essential domains： the Nterminal J-domain which includes the highly conserved HPD tripeptide, an adjacent domain that is rich in glycine and phenylalanine residues （G/F） and a Cysteine-rich zinc-finger domain with four repeats of CxxCxGxG that is important for protein interactions. The C-terminal of TaJ was -CAQQ, a farnesylation motif. The full-length deduced amino acid sequence of TaJ is highly homologous to J-domain proteins from various plant species. Southern blot analysis indicated that a single copy of TaJ existed in wheat genome. The expression pattern of TaJ performed by real-time PCR demonstrated that heat shock （HS） at 37℃ induced the expression of TaJ rapidly and strongly, but the response of the TaJ gene to cold stress was much slower than that to HS. Tissue-specific expression analysis showed that the expression level of TaJ gene was much higher in leaves than that in roots.     

The Growth Analysis in the Kernel Filling Process of K-Type Hybrid 901 and Its Parent Wheat

Using Matlab software, the grain filling process of hybrid wheat 901 and its parents was fitted by Richards equation W = A/（1 ＋ Be^-kt in order to study the characteristics of grain filling of the hybrid. The active grain growth period of the hybrid was 6 d longer than that of Shaan 229, and its final grain weight （43.7 g/1 000 grains） was higher than that of Shaan229 （36.3 g/1 000 grains）. N values of 901 and R205 were both less than 1, and their grain growth was faster in the early filling stage, while slower in the middle-late stage. N value of Shaan 229 was 〉1~ and its growth was slower in the early stage and faster in the middle stage. The period of early stage of 901 was shorter and of middle-late stage was longer. The situation of Shaan 229 was totally reversed. For parents, the father plant R205 was similar to hybrid wheat 901, whereas its mother plant K3314A similar to Shaan 229. It has been found that Richards equation was more suitable for fitting the grain filling process of wheat than Logistic equation.     

Ultrastructure of Slow-Rusting Expression of Wheat to Stripe Rust

The ultrastructure of wheat cultivars with slow-rusting resistance studied through TEM. The results show that slow-rusting has theinfection type resistance, but the mesophyll cell necrotized less inexpression to the stripe rust, Puccinia striiformis, wassame hypersensitive response characters with the low number, thereby only partially inhibiting the extension of rust fungus, and the fungus being inhibited and necrosed slighter in degree. Apart from the occurrence of hypersensitiveness, the response of the host cells in slow-rusting wheat cultivars to the infection of fungus also produces structural materials associated with defense reaction, but distinctly less than that in resistant cultivar. Thus, it is suggested that the slow-rusting resistance might have a similar mechanism with the low infection type resistance of race specificity,but with lower intensity.     

Molecular Characteristics of New Wheat Starch and Its Digestion Behaviours

In order to understand the effect of starch molecular characteristics on the gel structure, which subsequently influence the gel digestion behaviours, three wheat starches, control （conventional wheat starch）, two new wheat cultivars with different genetic backgrounds （by knocking out SBE IIb and SBE IIa, respectively） were used in this study. In comparison with control, slight differences in the morphology of the starch granules of new wheat 1 were observed, whereas the starch granules of new wheat 2 had irregular shapes both for A-type granules and B-type granules. Starch molecular weight size was determined by SE-HPLC, and the results indicate that there was a subtle increase in the amylose content in the starch of new wheat 1 compared to that of control. The starch of new wheat 2 had the highest amylose content, and the molecular weight （MW） of its amylopectin was the lowest among the three starches. Fourier transform infrared spectroscopy （FTIR） was employed to investigate starch gel structure and the results suggest that the molecules of starch gel from new wheat 2 are more likely to re-associate to form an organized conformation. The digestion behaviours of the three starch gels were measured using a mixture of pancreatin a-amylase and amyloglucosidase. The results indicated that the starch gels of control and new wheat 1 had very high digestibility of 91.7 and 91.9%, respectively, whereas the digestibility of wheat 2 starch gel was only 36.2%. In comparison with the digestion curve pattems of control and new wheat 1 starch gels, the new wheat 2 exhibited a much lower initial velocity. These results indicated that the molecules in the starch of new wheat 2 are more readily to re-associate to form an organized structure during gel formation because of its unique molecular characteristics.     

微丝骨架解聚剂在小麦-黄瓜白粉菌非寄主互作中的作用

 【目的】阐明微丝骨架在小麦非寄主抗病性中的作用。【方法】以小麦-黄瓜白粉菌非寄主互作体系为研究对象,通过台盼蓝、DAB和考马斯亮蓝染色法研究了小麦叶片经微丝骨架解聚剂处理后过敏性坏死、H2O2及乳突形成的变化。【结果】黄瓜白粉菌在小麦叶面上萌发明显滞后且附着胞多畸形。药剂处理后,过敏性坏死反应和H2O2的产生及乳突的形成均明显受抑,产生率均显著降低。白粉菌的侵入率明显提高,并且能形成吸器,偶尔还产生次生菌丝。【结论】微丝骨架参与了小麦的非寄主抗病性反应,骨架的聚合为抗病性反应的发生所必须。     

HrpN_(Ea)蛋白的结构与功能分析

Harpins是由革兰氏阴性植物病原细菌产生的一类蛋白激发子,对蛋白酶敏感,在非寄主植物叶片上可以诱导hypersensitive response（HR）或hypersensitive cell death（HCD）。HrpNEa是Harpins蛋白的一种,是从梨火疫病菌（Erwinia amylovora）中分离得到的。大量试验证明,HrpNEa蛋白在引起植物过敏反应的同时,能诱导植物获得性系统抗性及刺激植物生长发育。从分子生物学角度,利用国际互联网上的相关生物信息学分析软件NPSA、Swiss-Model、SAPS、InterPro Scan等对HrpNEa蛋白进行了结构和功能的预测分析。HrpNEa蛋白由403个氨基酸组成,有较多的β折叠和无规卷曲结构;HrpNEa蛋白无N端信号肽,不形成跨膜结构,定位于细胞质中。     

Whirly转录因子对非寄主菌诱导水稻HR反应的负调控作用

用RNA干扰技术研究了Whirly转录因子对水稻非寄主抗性反应HR的调控作用。PCR扩增编码Whirly转录因子的Oswhirly基因片段,分别以正向、反向顺序连接到载体pTCK303的两个多克隆位点中,构建Oswhirly基因沉默的RNA干扰载体pTCK303-Oswhy,经农杆菌EHA105菌株转化水稻细胞,结果发现转基因水稻细胞受非寄主菌诱导后,HR反应明显,细胞死亡率显著高于野生型及空载体转化水稻细胞。Oswhirly基因沉默导致HR反应增强,初步揭示Whirly转录因子可能是调控水稻HR反应的负调控因子。     

三种麦类作物对叶(冠)锈菌非寄主抗病性与品种抗病性的组织病理学研究

比较研究了小麦、黑麦和燕麦对小麦叶锈菌、黑麦叶锈菌和燕麦冠锈菌的非寄主抗病性与品种抗病性的组织病理学特点。接种幼苗的荧光显微检查表明,非寄主抗病性除不同程度地中断侵入外,主要抑制侵染菌丝生长和吸器母细胞的形成,引起菌落早期败育和叶肉细胞坏死。这些特点与品种抗病性的过敏性坏死反应相同。这种类型的抗病性具有小种专化性,因而即使用遗传操作技术将这种非寄主抗病性转移到寄主品种中,也可能因病菌小种的变异而不会持久。     

植物的超敏性细胞死亡研究初探

超敏反应(HR)是植物抗性反应激活所表现出的最为常见的特征。植物的超敏性细胞死亡在生物化学和形态学上有许多特征与动物的细胞凋亡相似,并且受寄主植物的 R基因和病原菌的avr 基因产物相互作用所控制,R基因产物与参与动物细胞凋亡的CED-4和APAF-1 蛋白有相似之处,因此,超敏性细胞死亡明显是细胞程序化死亡(PCD)的一种形式。HR中有多种信号分子的参与,活性氧是诱导 HR的一个重要因子,并且活性氧的产生与水杨酸(SA)有着直接的关系。HR很可能是作为一个信号系统而不是直接作为植物的一种防御机制。     

A plant vacuolar protease, VPE, mediates virus-induced hypersensitive cell death

Programmed cell death (PCD) in animals depends on caspase protease activity. Plants also exhibit PCD, for example as a response to pathogens, although a plant caspase remains elusive. Here we show that vacuolar processing enzyme (VPE) is a protease essential for a virus-induced hypersensitive response that involves PCD. VPE deficiency prevented virus-induced hypersensitive cell death in tobacco plants. VPE is structurally unrelated to caspases, although VPE has a caspase-1 activity. Thus, plants have evolved a regulated cellular suicide strategy that, unlike PCD of animals, is mediated by VPE and the cellular vacuole.     

微重力对细胞骨架影响的研究

介绍了近年来微重力对细胞骨架影响研究的进展;详细论述了微重力对细胞骨架的影响、地面模拟微重力的装置旋转生物反应器以及细胞骨架免疫双荧光染色技术等方面的问题。在微重力条件下,细胞骨架对力的作用非常敏感,微丝和微管的分布明显发生改变,主要表现为向细胞核集中分布,有序性下降,呈一定的弥散性趋势。     

植物与病原物互作中的活性氧代谢及其作用

介绍了活性氧的种类、代谢途径和测定方法,以及植物人存在的抗氧化机制、植物与病原物互作中活性氧的产生及遗传基础,重点对活性氧在植物与病原物互作中抗病信号转导、抗菌作用、膜脂氧化、细胞壁强化、植保素合成和过敏性细胞死亡等方面进行了综述。     

A Non-Marker Mutagenesis Strategy to Generate Poly-hrp Gene Mutants in the Rice Pathogen Xanthomonas oryzae pv.oryzicola

Xanthomonas oryzae pv.oryzicola (Xoc),the critical pathogen causing bacterial leaf streak in rice,possesses a hrp cluster that is responsible for triggering hypersensitive response (HR) in non-host tobacco and pathogenicity in host rice,and is considered to be one of the model pathogens in the rice model plant.Here,we developed a high-throughput mutagenesis system using a two-step integration mediated by a novel suicide vector pKMS1.It was used to generate single or poly-gene mutants of hpa1,hpa2,hrcV,hrpE,hpaB,and hrpF gene for functional analysis.In total,five single,four double,and two triple hrp gene mutants were constructed.The double and triple hrp gene deletion mutants triggered novel phenotypes in planta.Our data suggest that pKMS1 is a useful tool for non-marker mutagenesis of multiple genes in Xoc.     

阿米西达防治黄瓜白粉病的技术研究

[目的]研究黄瓜白粉病的防治技术。[方法]采用小株喷雾法、叶盘沾药漂浮法、叶盘漂浮法、叶盘沾药法和海绵垫叶盘漂浮法研究了瓜类白粉病菌对阿米西达的敏感性。[结果]测得小株喷雾法、叶盘沾药漂浮法、叶盘漂浮法、叶盘沾药法和海绵垫叶盘漂浮法的EC50分别为0.020 00、0.004 67、0.007 56、0.070 90和0.167 50μg/ml,表明叶盘沾药漂浮法最灵敏,叶盘漂浮法次之。叶盘漂浮法3次重复的EC50分别为0.007 75、0.007 56和0.007 80μg/ml,说明叶盘漂浮法的重复性好。叶盘漂浮法测定结果表明,阿米西达对瓜类白粉病的毒力比腈菌唑更强。25%阿米西达90和120μg/ml对黄瓜白粉病的防治效果显著优于对照药剂17%腈菌唑30μg/ml。[结论]阿米西达作为防治瓜类白粉病的高效药剂,可与腈菌唑等其他药剂交替使用。