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The rust fungus Puccinia graminis f. sp. tritici is an obligately biotrophic pathogen on wheat plants and thus difficult to investigate. Hence, little is known about this fungus at the molecular level. We constructed a differential suppression subtractive hybridization cDNA-library from rust-infected vs. healthy wheat plants. The majority of expressed sequence tags (ESTs) showed similarities to fungal sequences. Semiquantitative RT-PCR using mRNA from rust-infected leaves, and from axenically grown, differentiating and nondifferentiating young rust colonies as well as sporulating and nonsporulating mature mycelia revealed rather diverse expression patterns for different ESTs, shedding new light on their potential involvement in differentiation and host-pathogen interaction. 相似文献
224.
Ricardo B. Ferreira Sara Monteiro Regina Freitas Cláudia N. Santos Zhenjia Chen Luís M. Batista 《植物科学评论》2006,25(6):505-524
The attempted infection of a plant by a pathogen, such as a fungus or an Oomycete, may be regarded as a battle whose major weapons are proteins and smaller chemical compounds produced by both organisms. Indeed, plants produce an astonishing plethora of defense compounds that are still being discovered at a rapid pace. This pattern arose from a multi-million year, ping-pong?type co-evolution, in which plant and pathogen successively added new chemical weapons in this perpetual battle. As each defensive innovation was established in the host, new ways to circumvent it evolved in the pathogen. This complex co-evolution process probably explains not only the exquisite specificity observed between many pathogens and their hosts, but also the ineffectiveness or redundancy of some defensive genes which often encode enzymes with overlapping activities. Plants evolved a complex, multi-level series of structural and chemical barriers that are both constitutive or preformed and inducible. These defenses may involve strengthening of the cell wall, hypersensitive response (HR), oxidative burst, phytoalexins and pathogenesis-related (PR) proteins. The pathogen must successfully overcome these obstacles before it succeeds in causing disease. In some cases, it needs to modulate or modify plant cell metabolism to its own benefit and/or to abolish defense reactions. Central to the activation of plant responses is timely perception of the pathogen by the plant. A crucial role is played by elicitors which, depending on their mode of action, are broadly classified into nonspecific elicitors and highly specific elicitors or virulence effector/avirulence factors. A protein battle for penetration is then initiated, marking the pathogen attempted transition from extracellular to invasive growth before parasitism and disease can be established. Three major types of defense responses may be observed in plants: non-host resistance, host resistance, and host pathogenesis. Plant innate immunity may comprise a continuum from non-host resistance involving the detection of general elicitors to host-specific resistance involving detection of specific elicitors by R proteins. It was generally assumed that non-host resistance was based on passive mechanisms and that nonspecific rejection usually arose as a consequence of the non-host pathogen failure to breach the first lines of plant defense. However, recent evidence has blurred the clear-cut distinction among non-host resistance, host-specific resistance and disease. The same obstacles are also serious challenges for host pathogens, reducing their success rate significantly in causing disease. Indeed, even susceptible plants mount a (insufficient) defense response upon recognition of pathogen elicited molecular signals. Recent evidence suggests the occurrence of significant overlaps between the protein components and signalling pathways of these types of resistance, suggesting the existence of both shared and unique features for the three branches of plant innate immunity. 相似文献
225.
Mizuho Kusuda Mitsuhiro Ueda Yasuhito Konishi Yoshihito Araki Katsuji Yamanaka Masami Nakazawa Kazutaka Miyatake Takao Terashita 《Mycoscience》2006,47(4):184-189
We investigated extracellular carbohydrase production in the medium of an ectomycorrhizal fungus, Tricholoma matsutake, to reveal its ability to utilize carbohydrates such as starch as a growth substrate and to survey the saprotrophic aspects.
We found β-glucosidase activity in the static culture filtrate of this fungus. The β-glucosidase was purified and characterized.
The purified enzyme was obtained from about 2.1 l static culture filtrate, with 9.0% recovery, and showed a single protein
band on SDS-PAGE. Molecular mass was about 160 kDa. The enzyme was most active around 60°C and pH 5.0, and stable over a pH
of 4.0–8.0 for 30 min at 37°C. The purified enzyme was activated by the presence of Ca2+ and Mn2+ ions (about 2–3 times that of the control). The enzyme readily hydrolyzed oligosaccharides having a β-1,4-glucosidic linkage
such as cellobiose and cellotriose. However, it did not hydrolyze polysaccharides such as avicel and CM-cellulose or oligosaccharides
having an α-glucosidic linkage. Moreover, cellotriose was hydrolyzed by the enzyme for various durations, and the resultant
products were analyzed by TLC. We concluded that the enzyme from T. matsutake seems to be a β-glucosidase because cellotriose with a β-1,4-glucosidic linkage decomposed to glucose during the enzyme reaction. 相似文献
226.
AIMS: To monitor and select genetically characterized strains of Beauveria brongniartii to be used as microbiological control agents against Melolontha melolontha in different climatic conditions of the Valley of Aosta (northwest Italy). METHODS AND RESULTS: Molecular random amplified polymorphic DNA markers allowed monitoring of five B. brongniartii strains (C2, F, K2, N3 and W2) in field trials. Ten sites were chosen at Joven?an, Saint-Pierre and Quart areas, where a mixture of the five strains colonizing rye kernels was applied to the soil of each M. melolontha infested site. Growth, persistence and virulence on M. melolontha larvae of five fungal strains were evaluated in two subsequent 24-month studies. Beauveria brongniartii grew best at the Joven?an sites. Not only did strain F persist better than the other strains in most soil samples but it was also the most virulent strain. Strain F was isolated the most frequently from infected M. melolontha larvae recovered from the test sites. A general decrease in the larvae rate was detected in the test field soil. CONCLUSIONS: Strain F of B. brongniartii was better than other strains in growth, persistence and virulence against M. melolontha larvae in the test site soil. SIGNIFICANCE AND IMPACT OF THE STUDY: Results obtained from preliminary field trials support the use of strain F as a biological control agent against M. melolontha in the Valley of Aosta even if further targeted studies are still necessary. 相似文献
227.
Poor germination of mango seed due to fungal decay is a common problem in mango nurseries. The main causal fungus behind this problem is a black spore producing fungus, Syncephalastrum racemosum. This fungus exhibited high amylolytic activity and hence utilised the starch present in mango kernel for its own growth, thereby resulting in the death of emerging radical and plumule, which ultimately causes the death of emerging seedlings. A simple biocontrol device has been worked out by modifying the storage conditions of the mango seeds from aerobic to facultative. This change resulted in yeast growth on the pulp sticking to the mango seed, which in turn produced alcohol and prevented the growth of this fungus. The germination of such seeds has been found to be about 85–90%. 相似文献
228.
Kim HJ Vinale F Ghisalberti EL Worth CM Sivasithamparam K Skelton BW White AH 《Phytochemistry》2006,67(20):2277-2280
A sterile dark ectotrophic fungus isolated from roots of an Australian native grass, Neurachne alopecuroidea produces compound 1 in liquid cultures. The structure of the metabolite was determined by spectroscopic and X-ray diffraction studies. The metabolite shows activity against phytopathogens and plant growth promoting activity, properties that are also expressed in vivo by the ectotrophic fungus. 相似文献
229.
Using a flow-through chamber coupled with image analysis, the morphological parameters of 11 Mortierella species were quantified, and the relationship between micro- and macromorphology was investigated. On potato-dextrose-agar plates, 5 species formed rose petal-like colonies, 3 formed large round colonies, and 3 formed donut-like colonies. By observing micromorphology in a flow-through chamber, fungi were divided into 3 groups, classified according to morphological parameters: (i) a group with a high branch formation rate (q(b): tip/microm/h) and a low tip extension rate (q(tip): microm/tip/h); (ii) a group with a low branch formation rate and a high tip extension rate; and (iii) a group intermediate between the former and the latter groups. In suspension culture, group (i) fungi formed a hyphal bundle with a pulpy pellet-like morphology and a pellet core. In contrast, group (ii) fungi showed an aggregation of hyphae without the pellet core. In a narrow-specific hyphal growth rate (mu(l)) range (0.35-0.45 h(-1)), a higher branch formation rate led to increased hyphal branching, resulting in the formation of a hyphal bundle with a pulpy pellet-like morphology and a pellet core. When the branch formation rate was lower than 2 x 10(-3) tips/microm/h, the mycelia formed less branched but longer hypha. Our study surmises that a micromorphology consisting of a high hyphal growth rate (0.4 h(-1)), low tip extension rate (20 tips/microm/h), and high branch formation rate (8 x 10(-3) tips/microm/h) forms the suitable macromorphology for arachidonic acid production. 相似文献
230.
产高温蛋白酶微生物菌种资源的研究 总被引:24,自引:2,他引:24
对嗜温及嗜热微生物在不同环境中的分布及其产蛋白酶的情况进行了调查。研究结果显示从常温环境中也有可能分离到具有应用前景的嗜热菌菌株。 相似文献