A hypercellulolytic mutant of Fusarium oxysporum

Multiple mutagenesis of Fusarium oxysporum DSM 841 resulted in enhanced yields of cellulases. The hypercellulolytic mutant (NTG-19) secretes high levels of extracellular cellulases on different cellulosic substrates. Addition of surfactant, Tween-80, further increased enzyme secretion by about 30%. The results on hydrolysis of wheat straw by parent strain, DSM 841 and mutant NTG-19 cellulases also revealed a significant improvement in the hydrolytic potential of the cellulolytic enzymes from the mutant NTG-19.     

高等植物的3-羟基-3-甲基戊二酰辅酶A还原酶

介绍了植物3-羟基-3-甲基戊二酰辅酶A还原酶(HMGR)的结构和调控,并简略讨论了HMGR调控与植物类异戊二烯途径的关系.     

3-羟-3甲基戊二酰辅酶A还原酶及他汀类药物

3-羟-3甲基戊二酰辅酶A(HMG—CoA)还原酶是胆固醇合成的限速酶,它是胆固醇代谢的最重要的酶之一。HMG—CoA还原酶的抑制剂——他汀类药物是目前广泛用于临床的降脂药,它不但可降低血浆胆固醇水平,还可防止动脉粥样硬化。     

Fusarium oxysporum Forms Heterokaryons with Fusarium redolens

Vegetative compatibility among three isolates of Fusarium oxysporum f. sp. lupini and two isolates of F. oxysporum var. redolens from diseased lupins was investigated. Pairings between five mutants originated from each isolate revealed two compatibility groups. The first VCG comprised race 1 of F. oxysporum f. sp. lupini and one isolate of F. oxysporum var. redolens; the second VCG comprised race 2 of F. oxysporum f. sp. lupini and two isolates of F. oxysporum var. redolens. Heterokaryon formation was observed in many pairings involving mutants of both taxa. These findings provide evidence of the conspecificity of these two taxa and they support Gordon 's classification (1952) according to which F. redolens is actually F. oxysporum.     

A single gene in Fusarium oxysporum limits host range

Fusarium oxysoporum f. sp. radicis-cucumerinum (Forc) is able to cause disease in cucumber, melon, and watermelon, while F. oxysporum f. sp. melonis (Fom) can only infect melon plants. Earlier research showed that mobile chromosomes in Forc and Fom determine the difference in host range between Forc and Fom. By closely comparing these pathogenicity chromosomes combined with RNA-sequencing data, we selected 11 candidate genes that we tested for involvement in the difference in host range between Forc and Fom. One of these candidates is a putative effector gene on the Fom pathogenicity chromosome that has nonidentical homologs on the Forc pathogenicity chromosome. Four independent Forc transformants with this gene from Fom showed strongly reduced or no pathogenicity towards cucumber, while retaining pathogenicity towards melon and watermelon. This suggests that the protein encoded by this gene is recognized by an immune receptor in cucumber plants. This is the first time that a single gene has been demonstrated to determine a difference in host specificity between formae speciales of F. oxysporum.     

Nitrate Reductase and Nitrous Oxide Production by Fusarium oxysporum 11dn1 Under Aerobic and Anaerobic Conditions

The fungus Fusarium oxysporum 11dn1 was found to be able to grow and produce nitrous oxide on nitrate-containing medium in anaerobic conditions. The rate of nitrous oxide formation was three to six orders of magnitude lower than the rates of molecular nitrogen production by common denitrifying bacteria. Acetylene and ammonia did not affect the release of nitrous oxide release. It was shown that under anaerobic conditions fast increase of nitrate reductase activity occurred, caused by the synthesis of enzyme de novo and protein dephosphorylation. Reverse transfer of the mycelium to aerobic conditions led to a decline in nitrate reductase activity and stopped nitrous oxide production. The presence of two nitrate reductases was shown, which differed in molecular mass, location, temperature optima, and activity in nitrate- and ammonium-containing media. Two enzymes represent assimilatory and dissimilatory nitrate reductases, which are active in aerobic and anaerobic conditions, respectively. Received: 2 February 2000 / Accepted: 28 February 2000     

Occurrence of 3-Hydroxy-3-methyl-glutaryl Coenzyme A Reductase in Sweet Potato

Illumination of the dark-grown Euglena gracilis, both the wild-green type and a permanently bleached mutant, for 4 hr at 2,000 lux caused about 6-fold increase of the cellular content of total l-ascorbic acid. The increase was mainly due to an increase of reduced-form l-ascorbic acid. From the action spectrum only blue light was found to be effective for the increase. Darkening stopped the increase and reillumination started a renewed increase. The activity of l-gulono-γ-lactone dehydrogenase, catalyzing the last step of l-ascorbic acid biosynthesis, was also increased two fold by illumination for 2 hr, and was changed in parallel to that of the cellular content of l-ascorbic acid depending on the presence or absence of illumination. The augmentation of l-ascorbic acid formation was markedly inhibited by various inhibitors and uncouplers, but not by dichlorophenyldimethylurea. The results in sum suggest that the light-dependent increase of l-ascorbic acid formation in E. gracilis is not primarily associated with photosynthesis, but is apparently related to the adaptation of the dark-grown cells to the illuminated state.     

红斑肢痛症继发尖孢镰刀菌感染1例

报道红斑肢痛症继发尖孢镰刀菌感染1例。患者男,9岁。双小腿、双足间歇性红肿、热、痛2a,双下肢起脓疱、溃疡20d。溃疡部位脓液真菌培养为尖孢镰刀菌。患者经口服特比萘芬和局部治疗,溃疡愈合,真菌清除。     

Fusarium oxysporum: status in bioethanol production

Fermentation of lignocellulosic materials to ethanol and other solvents provides an alternative way of treating wastes and producing chemical feedstocks and fuel additives. Considerable efforts have been made in past 10 years to improve the process based on lignocellulosic biomass and hydrolysate that contains a complex mixture of sugars, decomposition products of sugars, and sometimes the inhibitory levels of soluble lignin. Despite the relative abundance of D-xylose in crop and forest residues it has not been found efficiently fermentable by most of the microorganisms. Recent research has revealed that D-xylose may be fermented to ethanol and organic acids. Recently, several strains of Fusarium oxysporum have been found to have potential for converting not only D-xylose, but also cellulose to ethanol in a one-step process. Distinguishing features of F. oxysporum for ethanol production in comparison to other organisms are identified. These include the advantage of in situ cellulase production and cellulose fermentation, pentose fermentation, and the tolerance of sugars and ethanol. The main disadvantage is the slow conversion rate when compared with yeast.     

Pathogen profile update: Fusarium oxysporum

Taxonomy: Kingdom Fungi; Phylum Ascomycota; Class Sordariomycetes; Order Hypocreales; Family Nectriaceae; genus Fusarium .
Host range: Very broad at the species level. More than 120 different formae speciales have been identified based on specificity to host species belonging to a wide range of plant families.
Disease symptoms: Initial symptoms of vascular wilt include vein clearing and leaf epinasty, followed by stunting, yellowing of the lower leaves, progressive wilting, defoliation and, finally, death of the plant. On fungal colonization, the vascular tissue turns brown, which is clearly visible in cross-sections of the stem. Some formae speciales are not primarily vascular pathogens, but cause foot and root rot or bulb rot.
Economic importance: Can cause severe losses in many vegetables and flowers, field crops, such as cotton, and plantation crops, such as banana, date palm and oil palm.
Control: Use of resistant varieties is the only practical measure for controlling the disease in the field. In glasshouses, soil sterilization can be performed.
Useful websites: http://www.broad.mit.edu/annotation/genome/fusarium_group/MultiHome.html ; http://www.fgsc.net/Fusarium/fushome.htm ; http://www.phi-base.org/query.php     

The mitochondrial genome of Fusarium oxysporum

Physical and genetic maps have been constructed for mtDNA from strains of the fungus Fusarium oxysporum representing three pathogenically specialized forms. All three mtDNA maps are circular. Their sizes are 45 kb for F. oxysporum f.sp. raphani and 52 kb for both F. oxysporum f.sp. conglutinans and F. oxysporum f.sp. matthioli. The genetic loci for cytochrome b, the mitochondrial 25S ribosomal RNA and cytochrome oxidase subunit II, have been identified and are similarly arranged on the three genomes.     

Arabidopsis defense response against Fusarium oxysporum

The plant fungal pathogen Fusarium oxysporum (Fox) is the causal agent of root rot or wilt diseases in several plant species, including crops such as tomato (Solanum lycopersicum), banana (Musa sapientum) and asparagus (Asparagus officinalis). Colonization of plants by Fox leads to the necrosis of the infected tissues, a subsequent collapse of vascular vessels and decay of the plant. Plant resistance to Fox appears to be monogenic or oligogenic depending on the host. Perception of Fox by plants follows the concept of elicitor-induced immune response, which in turn activates several plant defense signaling pathways. Here, we review the Fox-derived elicitors identified so far and the interaction among the different signaling pathways mediating plant resistance to Fox.     

Biliverdin Reductase B Dynamics Are Coupled to Coenzyme Binding

Biliverdin reductase B (BLVRB) is a newly identified cellular redox regulator that catalyzes the NADPH-dependent reduction of multiple substrates. Through mass spectrometry analysis, we identified high levels of BLVRB in mature red blood cells, highlighting the importance of BLVRB in redox regulation. The BLVRB conformational changes that occur during conezyme/substrate binding and the role of dynamics in BLVRB function, however, remain unknown. Through a combination of NMR, kinetics, and isothermal titration calorimetry studies, we determined that BLVRB binds its coenzyme 500-fold more tightly than its substrate. While the active site of apo BLVRB is highly dynamic on multiple timescales, active site dynamics are largely quenched within holo BLVRB, in which dynamics are redistributed to other regions of the enzyme. We show that a single point mutation of Arg78?Ala leads to both an increase in active site micro-millisecond motions and an increase in the microscopic rate constants of coenzyme binding. This demonstrates that altering BLVRB active site dynamics can directly cause a change in functional characteristics. Our studies thus address the solution behavior of apo and holo BLVRB and identify a role of enzyme dynamics in coenzyme binding.     

Developmental Regulation of Invertase Isozymes in Fusarium oxysporum

Fusarium invertase has two isozymes; one is developmentally regulated, whereas the other exists throughout the developmental stages of Fusarium.     

Cyclosporine A from a nonpathogenic Fusarium oxysporum suppressing Sclerotinia sclerotiorum

AIMS: To evaluate the antagonistic activity of Fusarium oxysporum nonpathogenic fungal strain S6 against the phytopathogenic fungus Sclerotinia sclerotiorum and to identify the antifungal compounds involved. METHODS AND RESULTS: The antagonistic activity of Fusarium oxysporum strain S6 was determined in vitro by dual cultures. The metabolite responsible for the activity was isolated by chromatographic techniques, purified and identified by spectroscopic methods as cyclosporine A. The antifungal activity against the pathogen was correlated with the presence of this metabolite by a dilution assay and then quantified. Cyclosporine A caused both growth inhibition and suppression of sclerotia formation. In a greenhouse assay, a significant increase in the number of surviving soybean (Glycine max) plants was observed when S. sclerotiorum and F. oxysporum (S6) were inoculated together when compared with plants inoculated with S. sclerotiorum alone. CONCLUSION: Fusarium oxysporum (S6) may be a good fungal biological control agent for S. sclerotiorum and cyclosporine A is the responsible metabolite involved in its antagonistic activity in vitro. SIGNIFICANCE AND IMPACT OF THE STUDY: Cyclosporine A has not been previously described as an inhibitor of S. sclerotiorum. Its minimum inhibitory concentration (MIC) of 0.1 microg disc(-1) makes it suitable to use as a biofungicide. In vivo experiments showed that F. oxysporum (S6) is a good candidate for the biocontrol of S. sclerotiorum in soybean.     

Sterol and Fatty Acid Metabolism in Fusarium oxysporum

The effects of temperatures ranging from 10°C to 35°C on sterol and fatty acid production and hydroxymethylglutaryl CoA reductase (EC 1.1,1.34, HMGCoA reductase) activity have been examined. Growth, based on dry weight, was maximal at 25°C to 30°C. Sterol production and the reductase activity were highest at 15°C after 28~32 hr incubation when the total fatty acids were minimal. Fatty acid unsaturation generally increased with decrease in temperature.     

Comparison of Fusarium oxysporum and Fusarium oxysporum var. redolens by Analyzing the Isozyme and Serological Patterns

Extracts from Fusarium oxysporum (F.o.) and F. oxysporum var. redolens (F.o.r.) isolates were compared by means of electrophoresis and crossed immunoelectrophoresis. The polymorphism of five isozyme systems allowed a distinction between F.o. and F.o.r. isolates. The isozyme patterns of three other isozyme systems did not allow this distinction between F.o. and F.o.r. to be made. Both fungi appeared almost identical serologically. Relative amounts of their corresponding proteins differed but the qualitative patterns of the proteins were nearly the same with the anti-F.o.r. serum, only one specific antigen was detected in the extracts from F.o.r., isolates. Although the results obtained indicate a strong similarity between F.o. and F.o.r., they are not sufficient for an unequivocal statement that the fungi belong to the same species.