Nasal allergy to fungi in guinea pigs

Sensitized guinea pigs produced specific IgG and IgE antibodies toward Cladosporium and Alternaria. In presence of fungal extracts, nasal mast cells degranulate. Ultrastructural modifications of the cells during degranulation have been established. The ciliary epithelium and the ciliary beating are not affected by fungal allergens.     

Cellulase production and activity in a species ofCladosporium

ACladosporium species produced large amounts of cellulase enzyme components when grown in shake-culture with medium containing carboxymethylcellulose. There was significantly less activity when Avicel, filter paper or cotton were used as substrates. KNO₃ was better than NH₄Cl or urea for the production of cellulase. Tween 80 at 0.1% (w/v) increased the production of cellulase by 1.5 to 4.5-fold. All the cellulase components were optimally active in the assay at pH 5.0 and 60°C.     

The Effect of Some Protein and Non-Protein Amino Acids on the Growth of Cladosporium herbarum and Trichothecium roseum

The effect of ten amino acids as the sole nitrogen source for the growth of Cladosporium herbarum (Link.) Fr. and Trichothecium roseum (Bull.) Link. was studied in order to clarify the fungus-host plant relationship. Special attention was paid to some rare non-protein amino acids of legumes. The best nitrogen sources for both fungi were γ-aminobutyric acid, arginine, serine and proline. Cladosporium could use homoarginine and canavanine, but these two amino acids were not used by Trichothecium when each was given as the only nitrogen source. Both fungi utilized ornithine, homoserine and a,γ-diaminobutyric acid to a limited extent. Pipecolic acid was not growth promoting. The growth-retarding effects of rare non-protein amino acids (homoarginine, canavanine, a,γ-diaminobutyric acid and pipecolic acid) were usually reversed by higher concentrations of their normal analogues. It is possible that rare non-protein amino acids may slightly protect the host plant against fungal infections, but there are clear differences between fungi in their reaction to non-protein amino acids.     

Population studies of the wild tomato species Solanum chilense reveal geographically structured major gene-mediated pathogen resistance

Natural plant populations encounter strong pathogen pressure and defence-associated genes are known to be under selection dependent on the pressure by the pathogens. Here, we use populations of the wild tomato Solanum chilense to investigate natural resistance against Cladosporium fulvum, a well-known ascomycete pathogen of domesticated tomatoes. Host populations used are from distinct geographical origins and share a defined evolutionary history. We show that distinct populations of S. chilense differ in resistance against the pathogen. Screening for major resistance gene-mediated pathogen recognition throughout the whole species showed clear geographical differences between populations and complete loss of pathogen recognition in the south of the species range. In addition, we observed high complexity in a homologues of Cladosporium resistance (Hcr) locus, underlying the recognition of C. fulvum, in central and northern populations. Our findings show that major gene-mediated recognition specificity is diverse in a natural plant-pathosystem. We place major gene resistance in a geographical context that also defined the evolutionary history of that species. Data suggest that the underlying loci are more complex than previously anticipated, with small-scale gene recombination being possibly responsible for maintaining balanced polymorphisms in the populations that experience pathogen pressure.     

黄瓜抗黑星病相关基因的差异表达分析

以抗黑星病黄瓜材料HX1为试材,接种黑星病菌（Cladosporium cucumerinum）2h、8h、20h、32h和72h的叶片作为试验方（Tester）,相应的未接种叶片作为对照方（Driver）,利用SSH技术,构建了黑星病菌侵染初期的正向和反向cDNA-SSH文库。用巢式引物PCR检测插入片段,获得了200个阳性克隆,通过测序,除去重复序列,共得到105个Unique ESTs。与非冗余蛋白数据库进行BLASTx比对,结果显示,17条ESTs未找到同源序列,88条非重复序列和已知基因的同源性较高,占全部ESTs序列的83.8%,其中86条ESTs与非冗余蛋白数据库已知功能的蛋白具有高度的相似性。结合高密度点阵膜杂交差异筛选,阳性率为75.0%。经初步分析这些序列的功能,差异表达的ESTs功能涉及能量和基础代谢、信号转导、蛋白和核酸代谢、光合作用及逆境中特异表达的基因等方面。为研究黄瓜抗黑星病基因提供了依据。     

Effect of opportunistic fungi on the life cycle of the root-knot nematode ( Meloidogyne javanica) on brinjal

The effect of four opportunistic fungi viz., Paecilomyces lilacinus, Cladosporium oxysporum, Gliocladium virens and Talaromyces flavus on the life cycle of the root-knot nematode, Meloidogyne javanica, on brinjal was evaluated under glasshouse conditions. The results revealed that these fungi affected the penetration and development of M. javanica. The life cycle of M. javanica was delayed by 10, 7, 4 and 2 days in the presence of P. lilacinus, C. oxysporum, G. virens and T. flavus respectively. Fecundity, number of eggs per eggmass and number of larvae was also reduced in the presence of these opportunistic fungi. However, the number of males increased in the presence of opportunistic fungi.     

产紫杉醇内生真菌枝状枝孢霉MD2的发酵条件优化

[目的]通过优化内生真菌枝状枝孢霉MD2的发酵条件,提高10-去乙酰巴卡亭Ⅲ (10-DAB)和紫杉醇(Taxol)的产量.[方法]采用单因素试验分析不同的培养基初始pH值、培养温度、摇床转速和培养时间对10-DAB和紫杉醇产量的影响,优化枝状枝孢霉MD2的培养条件;以YES为基本培养基,采用单因素试验和正交试验分析添加苯甲酸钠、苯丙氨酸、丝氨酸和甘氨酸4种前体物对10-DAB和紫杉醇产量的影响,优化枝状枝孢霉MD2的培养基组分.[结果]优化后发酵条件为:在初始pH为5.0的300 mL YES培养基中,添加15 mg/L苯甲酸钠、25 mg/L苯丙氨酸、5 mg/L丝氨酸、15 mg/L甘氨酸,接种1 mL枝状枝孢霉MD2的孢子悬液(107-10s个孢子/mL),28.0℃、220 r/min发酵培养12d.在此条件下,枝状枝孢霉MD2的生物量、10-DAB和紫杉醇的产量分别为15.5 g/L、471.5 μg/L和569.5 μg/L,与初始发酵条件相比,分别提高了1.3、3.6和3.4倍.[结论]首次获得了枝状枝孢霉MD2生产10-DAB和紫杉醇的较适摇瓶发酵条件,可为进一步放大发酵培养提供参考.     

A mutational analysis of the cytosolic domain of the tomato Cf‐9 disease‐resistance protein shows that membrane‐proximal residues are important for Avr9‐dependent necrosis

The tomato Cf‐9 gene encodes a membrane‐anchored glycoprotein that imparts race‐specific resistance against the tomato leaf mould fungus Cladosporium fulvum in response to the avirulence protein Avr9. Although the N‐terminal half of the extracellular leucine‐rich repeat (eLRR) domain of the Cf‐9 protein determines its specificity for Avr9, the C‐terminal half, including its small cytosolic domain, is postulated to be involved in signalling. The cytosolic domain of Cf‐9 carries several residues that are potential sites for ubiquitinylation or phosphorylation, or signals for endocytic uptake. A targeted mutagenesis approach was employed to investigate the roles of these residues and cellular processes in Avr9‐dependent necrosis triggered by Cf‐9. Our results indicate that the membrane‐proximal region of the cytosolic domain of Cf‐9 plays an important role in Cf‐9‐mediated necrosis, and two amino acids within this region, a threonine (T835) and a proline (P838), are particularly important for Cf‐9 function. An alanine mutation of T835 had no effect on Cf‐9 function, but an aspartic acid mutation, which mimics phosphorylation, reduced Cf‐9 function. We therefore postulate that phosphorylation/de‐phosphorylation of T835 could act as a molecular switch to determine whether Cf‐9 is in a primed or inactive state. Yeast two‐hybrid analysis was used to show that the cytosolic domain of Cf‐9 interacts with the cytosolic domain of tomato VAP27. This interaction could be disrupted by an alanine mutation of P838, whereas interaction with CITRX remained unaffected. We therefore postulate that a proline‐induced kink in the membrane‐proximal region of the cytosolic domain of Cf‐9 may be important for interaction with VAP27, which may, in turn, be important for Cf‐9 function.     

A conserved GH17 glycosyl hydrolase from plant pathogenic Dothideomycetes releases a DAMP causing cell death in tomato

To facilitate infection, pathogens deploy a plethora of effectors to suppress basal host immunity induced by exogenous microbe-associated or endogenous damage-associated molecular patterns (DAMPs). In this study, we have characterized family 17 glycosyl hydrolases of the tomato pathogen Cladosporium fulvum (CfGH17) and studied their role in infection. Heterologous expression of CfGH17-1 to 5 by potato virus X in different tomato cultivars showed that CfGH17-1 and CfGH17-5 enzymes induce cell death in Cf-0, Cf-1 and Cf-5 but not in Cf-Ecp3 tomato cultivars or tobacco. Moreover, CfGH17-1 orthologues from other phytopathogens, including Dothistroma septosporum and Mycosphaerella fijiensis, also trigger cell death in tomato. CfGH17-1 and CfGH17-5 are predicted to be β-1,3-glucanases and their enzymatic activity is required for the induction of cell death. CfGH17-1 hydrolyses laminarin, a linear 1,3-β-glucan with 1,6-β linkages. CfGH17-1 expression is down-regulated during the biotrophic phase of infection and up-regulated during the necrotrophic phase. Deletion of CfGH17-1 in C. fulvum did not reduce virulence on tomato, while constitutive expression of CfGH17-1 decreased virulence, suggesting that abundant presence of CfGH17-1 during biotrophic growth may release a DAMP that activates plant defence responses. Under natural conditions CfGH17-1 is suggested to play a role during saprophytic growth when the fungus thrives on dead host tissue, which is in line with its high levels of expression at late stages of infection when host tissues have become necrotic. We suggest that CfGH17-1 releases a DAMP from the host cell wall that is recognized by a yet unknown host plant receptor.