玉米KNOX基因家族鉴定及组织和逆境表达分析

为揭示玉米转录因子KNOX家族基因功能,采用生物信息学手段在玉米基因组水平鉴定KNOX家族成员,并对家族基因逆境和组织表达谱进行分析.结果 显示:(1)玉米基因组有22个ZmKNOX基因,根据其在染色体上的位置依次命名为ZmKNOX1-ZmKNOX22;编码蛋白质亚细胞定位预测发现,除ZmKNOX5、ZmKNOX11、...     

Correlation between screening procedures to select root endophytes for biological control of Fusarium verticillioides in Zea mays L

Biological control is an alternative to pesticides for protection against crop diseases. A key to progress in the field of biological control to protect maize against Fusarium verticillioides is to select in vitro the best agent to be applied in the field. This research was undertaken to evaluate the correlation between different screening methods and to suggest an adequate procedure that could be used to select bacterial agents with potential biocontrol against F. verticillioides in the maize rhizosphere. The results show an extensive Pearson correlation coefficient analysis between different screening procedures carried out for Arthrobacter spp., Azotobacter spp., Pseudomonas spp., and Bacillus spp. paired with 13 F. verticillioides strains isolated from maize endorhizosphere. The following screening methodologies were correlated: niche overlap index (NOI), indices of dominance, growth rate, lag phase, antibiosis, and fumonisin production. It was observed that NOI and antibiosis methodologies did not show any correlation. They were used to choose the best bacteria to apply under greenhouse conditions. Azotobacter armeniacus RC2 showed a NOI > 0.9 and inhibited all F. verticillioides strains assayed. Seed maize bacterization with A. armeniacus RC2 at 10⁶ and 10⁷ inoculum level resulted in significantly lower values of F. verticillioides counts compared to the control without bacteria at the root levels assayed. The analysis of variance indicated that there were significant interactions between two fungal repression assays. Antibiosis assays significantly correlated with greenhouse conditions (p < 0.01) at two inoculum levels tested. Therefore, the selection system adopted was adequate to choose the best bacterial biocontrol agent. The application of this methodology shows a way to outline the best biocontrol candidate.     

Incidence of the introduced parasitoids Cotesia kazak and Microplitis croceipes (Hymenoptera: Braconidae) from Helicoverpa armigera (Lepidoptera: Noctuidae) in tomatoes, sweet corn, and lucerne in New Zealand

Morphological defense traits of plants such as trichomes potentially compromise biological control in agroecosystems because they may hinder predation by natural enemies. To investigate whether plant trichomes hinder red imported fire ants, Solenopsis invicta Buren (Hymenoptera: Formicidae), as biological control agents in soybean, field and greenhouse experiments were conducted in which we manipulated fire ant density in plots of three soybean isolines varying in trichome density. Resulting treatment effects on the abundance of herbivores, other natural enemies, plant herbivory, and yield were assessed. Trichomes did not inhibit fire ants from foraging on plants in the field or in the greenhouse, and fire ant predation of herbivores in the field was actually greater on pubescent plants relative to glabrous plants. Consequently, fire ants more strongly reduced plant damage by herbivores on pubescent plants. This effect, however, did not translate into greater yield from pubescent plants at high fire ant densities. Intraguild predation by fire ants, in contrast, was weak, inconsistent, and did not vary with trichome density. Rather than hindering fire ant predation, therefore, soybean trichomes instead increased fire ant predation of herbivores resulting in enhanced tritrophic effects of fire ants on pubescent plants. This effect was likely the result of a functional response by fire ants to the greater abundance of caterpillar prey on pubescent plants. Given the ubiquity of lepidopteran herbivores and the functional response to prey shown by many generalist arthropod predators, a positive indirect effect of trichomes on predation by natural enemies might be more far more common than is currently appreciated.     

The role of phytohormones in basal resistance and Trichoderma-induced systemic resistance to Botrytis cinerea in Arabidopsis thaliana

Thirty-six phytohormone-affected mutants of Arabidopsis thaliana (L.) Heynh. and their parental ecotypes were tested for resistance/susceptibility to Botrytis cinerea Pers.; Fr. and ability to develop Trichoderma-mediated induced systemic resistance (ISR). Ecotype Colombia-0 (Col-0) was relatively resistant to B. cinerea, and Trichoderma harzianum Rifai T39 application at sites spatially separated (roots) from the B. cinerea inoculation (leaves) resulted in reduction of grey mold symptoms. Ecotypes Wassilewskija-4, Nossen-0 and Landsberg-0 had low levels of basal resistance to B. cinerea and were unable to express ISR. Mutants derived from ISR-non-inducible ecotypes displayed ISR-non-inducible phenotypes, whereas the ISR inducibility of mutants derived from the ISR-inducible genotype Col-0 varied according to the type of mutant. Thus, salicylic acid (SA)-impaired mutants derived from Col-0 were ISR-inducible, while ethylene/jasmonic acid (ethylene/JA)-impaired mutants of the same origin were ISR-non-inducible. SA-impaired mutants retained basal level of resistance to B. cinerea, while most ethylene/JA-impaired mutants were highly susceptible. Abscisic acid- and gibberellin-impaired mutants were highly susceptible to B. cinerea and showed ISR-non-inducible phenotypes irrespective of their lines of origin. Auxin-resistant mutants derived from Col-0 were ISR-inducible; mutant originating from Landsberg-0 and mutants which were resistant to both auxin and ethylene were ISR-non-inducible. Most of the arabidopsis genotypes which were unable to express Trichoderma-mediated ISR against B. cinerea exhibited enhanced susceptibility to this pathogen. T. harzianum treatments enhanced the growth of arabidopsis plants regardless of genotype or ISR inducibility.     

链球菌-韦荣菌共生对系统性疾病的诊断价值研究

口腔是人体生理功能的窗口,也是种类和数量繁多的微生物库.口腔微生态变化能够反映宿主与环境因素的相互作用,进而影响机体健康和疾病的进展.其中,链球菌属(Streptococcus)和韦荣菌属(Veillonella)是口腔最早的定殖菌和典型共生菌,共同参与口腔早期生物膜形成.大量研究显示,链球菌和韦荣菌共生失调不仅与龋病...     

珊瑚菜和滨旋花离体叶片代谢系统的耐热极限与夏季生长停滞机理的分析

为了解珊瑚菜(Glehnia littoralis)夏季生长停滞的原因,以其伴生种滨旋花(Calystegia soldanella)为参考,对他们的叶片代谢系统的耐热性进行了研究。结果表明,珊瑚菜叶片光合作用的失活温度和膜透性的半致死温度均比滨旋花低大约5℃。珊瑚菜和滨旋花在温度为50℃时仍然保持很高的的呼吸速率(仅分别下降10%和24%),明显高于各自的光合系统和质膜系统的耐热温度。高斯回归分析表明,珊瑚菜的光合速率与呼吸速率比明显低于滨旋花。因此,高温下的光合产物昼夜过度消耗可能是珊瑚菜夏天生长停滞的原因,也可能与其整体较低的耐热性有关。     

Induction of PR proteins and resistance by the biocontrol agent Clonostachys rosea in wheat plants infected with Fusarium culmorum

Clonostachys rosea (CR) is a common worldwide saprophyte with destructive effect against several plant pathogenic fungi showing antagonistic features against a wide variety of pathogens. We recently isolated a strain of C. rosea, named CR47, from wheat crown infected with Fusarium culmorum (FC); this strain proved to be effective against Fusarium seed borne diseases of cereals under field condition. In this paper the function of C. rosea applied as seed treatment on wheat seedling growth was investigated. In addition, we investigated the expression pattern of peroxidases and chitinases as well as PR4 proteins following both CR treatments of seeds and FC infection and also in the three-component system pathogen–antagonist–wheat. Several chitinase isoforms were induced by CR-treatment both in coleoptiles and roots, whereas some peroxidase isoforms were induced only in the presence of both antagonist and pathogen. In the latter case, it seems that CR-treatment by itself promotes plant growth and reduces the peroxidase expression, while enhances some chitinase isoforms probably involved in cell wall disruption. Moreover, both the antagonist and the pathogen studied induced PR4 protein expression, which probably exerts its role on the invading microorganisms by a translation-inhibitory process that could be ascribed to their ribonuclease activity.     

Effects of Bt maize-fed prey on the generalist predator <Emphasis Type="Italic">Poecilus cupreus</Emphasis> L. (Coleoptera: Carabidae)

We investigated the effects of transgenic maize (Zea mays) expressing Bacillus thuringienses toxin (Bt maize) on larval and adult Poecilus cupreus carabid beetles in laboratory studies. In no-choice trials, neonate P. cupreus larvae were fed exclusively with Spodoptera littoralis caterpillars, which had been raised on Bt maize. S. littoralis raised on conventional maize or high quality Calliphora sp. pupae were fed to the beetle larvae in two control treatments. Bt-maize-fed caterpillar prey increased mortality to 100 within 40days. The experiment was repeated with 10-day-old beetle larvae. Bt treatment resulted in fewer pupae than in both controls, and in a higher mortality than in the Calliphora control. S. littoralis was suitable as exclusive prey in no-choice tests, at least for 40days, although prey quality seemed to be low compared to Calliphora pupae. The observed effects are most likely indirect effects due to further reduced nutritional prey quality. However, direct effects cannot be excluded. In the second part of the study, exposure of P. cupreus to Bt intoxicated prey was examined in paired-choice tests. Adult beetles were offered a choice between different prey conditions (frozen and thawed, freshly killed or living), prey types (S. littoralis caterpillars, Calliphorasp. pupae, cereal aphids) and prey treatments (raised on Bt or conventional maize). Living prey was preferred to frozen and dead prey. Caterpillars were only preferred to fly pupae and aphids when living. Prey treatment seemed to be least important for prey selection. The tests showed that P. cupreus ingested caterpillars readily and there was no evidence of them avoiding Bt containing prey, which means exposure in the field could occur. The presented protocols are a first step towards ecological risk assessment for carabid beetles.     

桉树杂交种对桉树枝瘿姬小蜂的抗性变异分析

植物种间杂交是一种普遍自然现象,杂交往往造成植物表型及生理变异,从而改变杂种抗虫性。与亲本种相比,杂种抗虫性可能增强或减弱,也有可能处于与亲本相似水平。初生、次生代谢物的质变与量变是引起杂种抗虫性变异的重要原因。近年来,桉树杂交育种已在世界范围内广泛应用并取得了显著成效,桉树杂交种间抗虫性表现参差不齐,因此,桉树是研究杂交种抗虫性变异机制的理想材料。以2个桉树杂交种巨细桉DH201-2、巨尾桉G9及桉树重要害虫桉树枝瘿姬小蜂为研究对象,比较了2个杂交种与其纯亲本种[(巨桉×细叶桉),(巨桉×尾叶桉)]间的抗虫性差异;同时,综合比较了品系间叶片性状(叶片厚度、含水率、比叶面积)、初生化合物(C、N、可溶性糖、可溶性蛋白)及次生化合物(总酚、单宁)差异,以研究桉树杂交种抗虫性变异的理化机制。结果表明:DH201-2感染桉树枝瘿姬小蜂的虫瘿数目显著高于其双亲本种,而G9上虫瘿数目显著低于其双亲本种。DH201-2与G9的叶片厚度与巨桉相近,而显著薄于另一亲本种。DH201-2叶片含水率显著高于细叶桉、与巨桉相近;G9叶片含水率则显著低于其双亲本种。相似的是,DH201-2和G9的比叶面积均显著高于其双亲本种。初生化合物方面,DH201-2叶片可溶性糖和可溶性蛋白含量均显著高于其亲本种,N含量则仅高于细叶桉;而G9叶片可溶性蛋白含量虽高于其双亲本种,可溶性糖含量则无显著差异,N含量显著低于其双亲本种。次生化合物方面,DH201-2叶片总酚和单宁含量显著低于其双亲本种,而G9则显著高于其双亲本种。因此,与其亲本种相比,DH201-2感虫性增加,而G9抗虫性增加;与桉树枝瘿姬小蜂发育相关的营养指标(如含水率、可溶性糖、N含量)及次生防御物质(如总酚、缩合单宁)在桉树杂交种组织内的含量差异影响了桉树杂交种对桉树枝瘿姬小蜂的抗性。在全球推行桉树杂交育种且桉树害虫数量逐年增加的大背景下,应加强对桉树杂交种抗虫性机制研究,为选育高抗品系及桉树产业可持续发展提供理论指导。     

末端氧化酶CyxA增强肺炎克雷伯菌对外界环境的抵抗力及致病性

【背景】细胞色素bd末端氧化酶存在于许多致病菌中,保护细菌免受各种不利环境应激的损害,促进多种致病菌的毒力,由于真核生物缺乏这种酶,被认为是开发新型抗菌药物的一个有前景的靶标,肺炎克雷伯菌(以下简称“肺克”)中末端氧化酶的作用至今尚不清楚。【目的】探究末端氧化酶CyxA在肺炎克雷伯菌中的生物学功能。【方法】构建cyxA基因无痕缺失株与回补株,通过体外实验比较野生株WT及敲除株ΔcyxA的生长能力、生物被膜和荚膜合成能力、对不同环境因素(酸性、高渗、氧化、还原)及抗生素的抵抗力,同时结合体内感染实验分析CyxA对肺克致病性的作用。【结果】缺失cyxA基因后肺克体外有氧生长能力明显降低,生物被膜和荚膜合成能力无差异,对pH 5.5、1.9%氯化钠、过氧化氢、β-巯基乙醇和部分β-内酰胺类及氨基糖苷类抗生素的抵抗力降低。通过小鼠滴鼻实验发现缺失cyxA基因后肺克的致病性降低。【结论】本研究首次证实末端氧化酶CyxA促进肺克有氧生长,增强该菌对酸性、高渗、氧化还原环境及部分抗生素的抵抗力,从而增强肺克的致病性。该研究为进一步阐明末端氧化酶对肺克致病性的分子机制奠定基础,为后续开发靶向肺克末端氧化酶的新型抗菌药物提供参考。     

Induction of anterior neural fates in the ascidian Ciona intestinalis

The sensory vesicle of ascidians is thought to be homologous to the vertebrate forebrain and midbrain (Development 125 (1998) 1113). Here we report the isolation of two sensory vesicle markers in the ascidian Ciona intestinalis, which are homologs of vertebrate otx and gsx homeobox genes. By using these markers to analyze the induction of anterior neural tissue in Ciona, we find that the restriction of anterior neural fate to the progeny of the anterior animal blastomeres is due to a combination of two factors. The vegetal blastomeres show a differential inducing activity along the anterior-posterior axis, while the competence to respond to this inducing signal is markedly higher in the anterior animal blastomeres than in the posterior animal blastomeres. This differential competence to respond is also observed in response to bFGF, a candidate neural inducer in ascidians (J. Physiol. 511.2 (1998) 347) and can be detected by the gastrula stage. Our results, however, indicate that bFGF can only induce a subset of the responses of the endogenous inducer, suggesting that additional signals in the embryo are necessary to induce a fully patterned nervous system.     

Fatty acid composition of lipids from mushrooms belonging to the family Boletaceae

The non-polar lipid content and fatty acid (FA) composition of 11 mushroom species of the family Boletaceae were determined. The non-polar lipid content ranged from 2.0 (Leccinum aurantiacum and Boletus erythropus) to 5.4 % (w/w) d.w. (Suillus grevillei) with an average value of 2.9 %. More than 25 different FAs were found in the mushroom lipids. Unsaturated FAs, mainly linoleic and oleic acids, accounted for about 83 % of the total FAs, while palmitic acid was the main saturated FA. Some FAs are identified for the first time in Boletaceae and in higher Basidiomycetes (cis-11,12-methyleneoctadecanoic acid, 7-cis,10-cis hexadecadienoic) or in fungi (cis-11,12-methyleneoctadecanoic acid). There were significant differences (P < 0.05) in the contents of specific FAs between mushroom species.     

Characterization of biocontrol traits in the entomopathogenic nematode Heterorhabditis georgiana (Kesha strain), and phylogenetic analysis of the nematode’s symbiotic bacteria

Our objective was to estimate the biocontrol potential of the recently discovered entomopathogenic nematode species Heterorhabditis georgiana (Kesha strain). Additionally, we conducted a phylogenetic characterization of the nematode’s symbiotic bacterium. In laboratory experiments, we compared H. georgiana to other entomopathogenic nematodes for virulence, environmental tolerance (to heat, desiccation, and cold), and host seeking ability. Virulence assays targeted Acheta domesticus, Agrotis ipsilon, Diaprepes abbreviatus, Musca domestica, Plodia interpunctella, Solenopsis invicta, and Tenebrio molitor. Each assay included H. georgiana and five or six of the following species: Heterorhabditis floridensis, Heterorhabditis indica, Heterorhabditis mexicana, Steinernema carpocapsae, Steinernema feltiae, Steinernema rarum, and Steinernema riobrave. Environmental tolerance assays included Heterorhabditis bacteriophora, H. georgiana, H. indica, S. carpocapsae, S. feltiae, and S. riobrave (except cold tolerance did not include S. carpocapsae or S. riobrave). Host seeking ability was assessed in H. bacteriophora, H. georgiana, S. carpocapsae, and Steinernema glaseri, all of which showed positive orientation to the host with S. glaseri having greater movement toward the host than S. carpocapsae (and the heterorhabditids being intermediate). Temperature range data (tested at 10, 13, 17, 25, 30 and 35 °C) indicated that H. georgiana can infect Galleria mellonella between 13 and 35 °C (with higher infection at 17–30 °C), and could reproduce between 17 and 30 °C (with higher nematode yields at 25 °C). Compared with other nematode species, H. georgiana expressed low or intermediate capabilities in all virulence and environmental tolerance assays indicating a relatively low biocontrol potential. Some novel observations resulted from comparisons among other species tested. In virulence assays, H. indica caused the highest mortality in P. interpunctella followed by S. riobrave; S. carpocapsae caused the highest mortality in A. domesticus followed by H. indica; and S. riobrave was the most virulent nematode to S. invicta. In cold tolerance, S. feltiae exhibited superior ability to cause mortality in G. mellonella (100%) at 10 °C, yet H. bacteriophora and H. georgiana exhibited the ability to produce attenuated infections at 10 °C, i.e., the infections resumed and produced mortality at 25 °C. In contrast, H. indica did not show an ability to cause attenuated infections. Based on the phylogenetic analysis, the bacterium associated with H. georgiana was identified as Photorhabdus luminescens akhurstii.     

Stimulatory effects of potassium iodide on auxin action in the coleoptile segments of maize (Zea mays)

Potassium iodide (KI) was found to stimulate IAA-induced elongation of coleoptile segments in maize (Zea mays L.). The promoting effects of KI on coleoptile elongation, which were optimal at 1 mM in the presence of IAA, did not occur as a result of better conservation of IAA in the incubation medium. In addition, KI did not affect fusicoccin- or epibrassinolide-induced elongation. Additionally, sodium iodide (NaI) induced similar stimulatory effects on IAA-induced elongation, however, potassium chloride (KCl) showed no effect, suggesting that iodide is the active component. KI also enhanced IAA-induced ethylene biosynthesis in maize coleoptile segments. Taken together, these results suggest the involvement of KI-sensitive step(s) in auxin action before effectors of the signal transduction pathway split to elongation growth and ethylene biosynthesis. In-yong Hwang and Soo Chul Chang contributed equally to this work.     

A specific enzyme hydrolyzing 6-O(4-O)-indole-3-ylacetyl-β-d-glucose in immature kernels of Zea mays

The purification of 6-O(4-O)-indole-3-ylacetyl-beta-D-glucose (IAGlc) hydrolase from immature kernels of maize (Zea mays) was undertaken to separate this enzyme from 1-O-IAGlc hydrolase and beta-glucosidase. Partially purified 6-O(4-O)-IAGlc hydrolase was found to be the specific enzyme catalyzing hydrolysis of stable esters of IAA and glucose. Among a range of ester conjugates tested as substrates, only 6-O(4-O)-IAA-glucose and IBA-glucose isomers were effectively hydrolyzed. No activity against p-nitrophenyl-beta-D-glucopyranoside, a synthetic substrate for beta-glucosidase, was detected in the enzyme preparation. The enzyme is probably involved in the regulation of the IAA levels by the target release of free auxin from ester-linked conjugates, its inactive storage forms.     

Role of salicylic acid in systemic resistance induced by Pseudomonas fluorescens against Fusarium oxysporum f. sp. ciceri in chickpea

Selected isolates of Pseudomonas fluorescens (Pf1-94, Pf4-92, Pf12-94, Pf151-94 and Pf179-94) and chemical resistance inducers (salicylic acid, acetylsalicylic acid, DL-norvaline, indole-3-carbinol and lichenan) were examined for growth promotion and induced systemic resistance against Fusarium wilt of chickpea. A marked increase in shoot and root length was observed in P. fluorescens treated plants. The isolates of P. fluorescens systemically induced resistance against Fusarium wilt of chickpea caused by Fusarium. oxysporum f.sp. ciceri (FocRs1), and significantly (P = 0.05) reduced the wilt disease by 26-50% as compared to control. Varied degree of protection against Fusarium wilt was recorded with chemical inducers. The reduction in disease was more pronounced when chemical inducers were applied with P. fluorescens. Among chemical inducers, SA showed the highest protection of chickpea seedlings against wilting. Fifty two- to 64% reduction of wilting was observed in soil treated with isolate Pf4-92 along with chemical inducers. A significant (P = 0.05; r = -0.946) negative correlation was observed in concentration of salicylic acid and mycelial growth of FocRs1 and at a concentration of 2000 microg ml(-1) mycelial growth was completely arrested. Exogenously supplied SA also stimulated systemic resistance against wilt and reduced the disease severity by 23% and 43% in the plants treated with 40 and 80 microg ml(-1) of SA through root application. All the isolates of P. fluorescens produced SA in synthetic medium and in root tissues. HPLC analysis indicated that Pf4-92 produced comparatively more SA than the other isolates. 1700 to 2000 nanog SA g(-1) fresh root was detected from the application site of root after one day of bacterization whereas, the amount of SA at distant site ranged between 400-500 nanog. After three days of bacterization the SA level decreased and was found more or less equal at both the detection sites.     

Variation in damage to cotton affecting larval feeding preference of Spodoptera littoralis

Feeding experiments with larvae of Spodoptera littoralis were performed with leaves from cotton plants subjected to damage and from undamaged plants. In the experiments, four different time intervals (1, 3, 7, and 14 days) after damage induction and two different levels (high and low) of herbivore damage were tested. Seven days after damage induction larvae fed less on the young top leaves from damaged plants for both levels of damage. At the high damage level, the larvae fed less on leaves from the damaged plants after just three days, and this effect still remained 14 days after damage infliction. When mature leaves from the middle of the plant were compared, no difference between treatments was observed.Two plant sizes were tested, small plants with 4–5 true leaves and large plants with 8–10 true leaves. In small plants the induced changes affecting larval feeding were found mainly in the youngest leaf at the top of the plant, while in large plants the induced effects were found in both the youngest and the second youngest leaves.In plants subjected to artificial damage, larvae fed less on top leaves of the damaged plants when compared to leaves from undamaged plants. When leaves from plants that had been artificially damaged were directly compared with leaves from plants damaged by herbivores, larvae fed more on the youngest leaves from artificially damaged plants when the plants were large. In small plants no significant difference was found when comparing artificial and herbivore damage.