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1.
R. E. Mitchell 《Cellular and molecular life sciences : CMLS》1991,47(8):791-803
This review attempts to rationalise what is known about bacterial phytotoxins and associate it with the ecology and possible evolution of the producing organisms. Study of non-toxin producing variants gives insight into the ecological role of the toxin. Elucidation of chemical structures of phytotoxins has shown that many exist as families of analogous compounds. Studies on the variation of chemical structures and how they are distributed across species and genera can lead to development of hypotheses on evolutionary relationships. Knowledge on biosynthetic pathways to tosins allows recognition of specific enzymatic steps involved in developing the characteristic features of the structures. Phytotoxins often have a potent biochemical activity, and in some cases the producing organism has associated mechanisms to prevent action of the toxin upon itself; in such cases toxigenesis is clearly not a chance event. The various aspects of bacterial toxigenesis indicate that bacterial phytotoxins are special secondary metabolic products that play beneficial roles to the producing organisms in their various ecological niches. 相似文献
2.
Phytotoxins as potential herbicides 总被引:7,自引:0,他引:7
G. Strobel D. Kenfield G. Bunkers F. Sugawara J. Clardy 《Cellular and molecular life sciences : CMLS》1991,47(8):819-826
Phytotoxins are produced in various culture media by many fungi that are pathogenic to weeds. These phytotoxins belong to a wide array of chemical substances including sesquiterpenoids, sesterterpenoids, diketopiperazines, peptides, spirocyclic lactams, isocoumarins, and polyketides. In most cases, the phytotoxin belongs to a family of related compounds produced by the fungus. These related compounds may or may not be phytotoxins. Phytotoxin production, in some cases, is optimized by the addition of a host extract to the culture medium. Biological activity is usually observed in a range of concentrations from 10–3 to 10–6 M. The concept of using these molecules, derivatives thereof, or related compounds as herbicides should be explored. 相似文献
3.
A. Graniti 《Cellular and molecular life sciences : CMLS》1991,47(8):751-755
Bacterial and fungal plant pathogens are known to produce diffusible toxins in infected plants. These phytotoxins are harmful to plants in very low concentrations, and many reproduce at least some of the symptoms of the relevant bacterial or fungal disease. Several phytotoxins have been shown to be involved in pathogenesis. Recent years have seen substantial progress in our knowledge about the nature, structure and mode of action of phytotoxins, and this is briefly reviewed. Finally, possible applications in fields other than plant pathology are mentioned.The Editors wish to thank Prof. A. Ballio and Prof. A. Graniti for coordinating this multi-author review. 相似文献
4.
A. A. Stierle R. Upadhyay J. Hershenhorn G. A. Strobel G. Molina 《Cellular and molecular life sciences : CMLS》1991,47(8):853-859
Black Sigatoka is the most costly to control disease of bananas and plantains in the world. Currently, a worldwide search is underway either to find or to produce cultivars that are disease-resistant or-tolerant. Phytotoxins isolated from the pathogen might facilitate the discovery of such cultivars. Several aromatic compounds from liquid cultures ofMycosphaerella fijiensis, the causal agent of Black Sigatoka disease of bananas and plantains, have been isolated. The most abundant and phytotoxic of these compounds is 2,4,8-trihydroxytetralone, which induces necrotic lesions at 5 g/5 l in less than 12 h on sensitive cultivars of bananas. This compound exhibits host-selectivity that mimics that of the pathogen. Other phytotoxins isolated from this fungus, in lesser amounts, were juglone, the novel compound 2-carboxy-3-hydroxycinnamic acid, isoochracinic acid and 4-hydroxyscytalone. Some of the phytotoxins isolated are melanin shunt pathway metabolites, which makes this fungus unique among plant pathogens. 相似文献
5.
Ferreri C Kratzsch S Landi L Brede O 《Cellular and molecular life sciences : CMLS》2005,62(7-8):834-847
Thiyl radicals are intermediates of enzyme- and radical-driven biochemical processes, and their potential as reactive species in the biological environment has been somehow underestimated. From organic chemistry, however, it is known that thiyl radicals isomerize the double bonds of unsaturated fatty acids to a mixture with very dominating trans isomers. Recently, this reaction has been particularly studied for biosystems, focusing on the effect of thiyl radicals on the natural all-cis double bonds of unsaturated phospholipids, which undergo a conversion to the unnatural trans form. In this paper we report briefly the role of thiyl radicals in biosystems, describe the main features of the radical-induced cis-trans isomerization process under both in vitro and in vivo conditions, and reflect on some consequences for membrane structures, lipid metabolism and enzymatic reactions.Received 29 October 2004; received after revision 3 December 2004; accepted 4 January 2005 相似文献
6.
E. A. Marcus T. G. Nolen C. H. Rankin M. Stopfer T. J. Carew 《Cellular and molecular life sciences : CMLS》1988,44(5):415-423
Summary A set of fundamental issues in neuroethology concerns the neural mechanisms underlying behavior and behavioral plasticity. We have recently analyzed these issues by combining a simple systems approach in the marine molluscAplysia with a developmental analysis aimed at examining the emergence and maturation of different forms of behavior and learning. We have focussed on two kinds of questions: 1) How are specific neural circuits developmentally assembled to mediate different types of behaviors? and 2) how is plasticity integrated with these circuits to give rise to different forms of learning? From our analysis of the development of learning and memory inAplysia, several themes have emerged: 1) Different forms of learning emerge according to different developmental timetables. 2) Cellular analogs of learning have the same developmental timetables as their respective forms of behavioral learing. 3) An analysis of non-decremented responses prior to the emergence of sensitization reveals a novel inhibitory process on both behavioral and cellular levels. 4) Sensitization emerges simultaneously in diverse response systems, suggesting an underlying general process. 5) A widespread proliferation of central neurons occurs in the same developmental stage as the emergence of sensitization, raising the possibility that some aspect of the trigger for neuronal proliferation may also contribute to the expression of sensitization. 相似文献
7.
H. Riezman A. Munn M. I. Geli L. Hicke 《Cellular and molecular life sciences : CMLS》1996,52(12):1033-1041
Endocytosis is a general term that is used to describe the internalization of external and plasma membrane molecules into the cell interior. In fact, several different mechanisms exist for the internalization step of this process. In this review we emphasize the work on the actin-dependent pathways, in particular in the yeastSaccharomyces cerevisiae, because several components of the molecular machinery are identified. In this yeast, the analysis of endocytosis in various mutants reveals a requirement for actin, calmodulin, a type I myosin, as well as a number of other proteins that affect actin dynamics. Some of these proteins have homology to proteins in animal cells that are believed to be involved in endocytosis. In addition, the demonstration that ubiquitination of some cell surface molecules is required for their efficient internalization is described. We compare the actin, myosin and ubiquitin requirements for endocytosis with recent results found studying these processes usingDictyostelium discoideum and animal cells. 相似文献
8.
Summary
Agrobacterium tumefaciens A208 with nopaline plasmid pTiT37 was used to obtain stem tumors on plantlets ofFagraea fragrans grown in vitro. Bacterial elimination and tissue proliferation were simultaneously achieved by growing tumors on cefatoxime medium. After some tissue growth the shoots regenerated. An examination of these showed the presence of nopaline, indicating genetic transformation by T-DNA. 相似文献
9.
R. P. Scheffer 《Cellular and molecular life sciences : CMLS》1991,47(8):804-811
Many fungal pathogens of plants adapt readily to changes in agriculture. Among the most revealing is a fungal group whose species produce host-selective toxins as key determinants of disease. Several lines of evidence support the hypothesis that these fungi evolved from opportunistic, low-grade pathogens by gaining new genetic information leading to toxin production; in some species, toxin production is known to be under single gene control. as a result of this evolution, these fungi became virulent and host-specialized. The best-known model cases belong to the generaCochliobolus andAlternaria; there are suggestions of evolutionary lines among these genera, with species that range from saprophytes to opportunists to specialized pathogens. Host specialization can lead to genetic isolation, a first step in speciation. Ability to produce host-selective toxin has allowed these fungi to exploit the monocultures and genetic uniformity of modern agriculture. Destructive epidemics have been the result. 相似文献
10.
Summary A new aryl hydrazone structure with high insecticidal activity against the Australian sheep blowfly,Lucilia cuprina, was shown to have a higher activity as an uncoupler of oxidative phosphorylation in insect compared to mammalian mitochondrial preparations. This compound possesses the requirements of other uncouplers in its measured pKa and lipid solubility. However, when compared to a closely related structure with similar physicochemical properties, its insecticidal and insect mitochondrial uncoupling activities are greater and it exhibits decreased mammalian toxicity corresponding to this differential biochemical selectivity.Acknowledgment. We thank Mr K. Rihs for preparation of the hydrazones and Prof. Dr K.H. Büchel for supply of hydrazone III. 相似文献
11.
Highly active metabolites have been detected in the hemolymph of the lepidopteranSpodoptera exigua infected with the mycopathogen,Beauveria bassiana. A combination of phenyl sepharose and CM ion exchange chromatography was utilized to extract the active metabolites from infected hemolymph samples. The active in vivo metabolites, having a molecular mass greater than 10 KDa, were thermolabile and were inactivated by proteinase K. These metabolites were characterized by their ability to disrupt metamorphosis, killing treated larvae at the wandering or pupal stage. Additionally, injection ofS. exigua larvae with active samples caused a reduction in the number of filopodial-producing hemocytes. The biological activities and biochemical properties suggest that novel compounds are produced duringB. bassiana mycosis. 相似文献
12.
Summary It was found that some ciliates,Stentor, Spirostomum andBlepharisma, which can contract rapidly like the stalks of Vorticellidae, have Ca2+-binding proteins that are very similar to spasmins, in the immunological sense. The presence of spasmins in other Protozoa and in some Metazoa was also investigated. 相似文献
13.
Human bystin was identified as a cytoplasmic protein directly binding to trophinin, a cell adhesion molecule potentially involved
in human embryo implantation. Although the trophinin gene is unique to mammals, the bystin gene (BYSL) is conserved across eukaryotes. Recent studies show that bystin plays a key role during the transition from silent trophectoderm
to an active trophoblast upon trophinin-mediated cell adhesion. Bystin gene knockout and knockdown experiments demonstrate
that bystin is essential for embryonic stem cell survival and trophectoderm development in the mouse. Furthermore, biochemical
analysis of bystin in human cancer cells and mouse embryos indicates a function in ribosomal biogenesis, specifically in processing
of 18S RNA in the 40S subunit. Strong evidence that BYSL is a target of c-MYC is consistent with a role for bystin in rapid protein synthesis, which is required for actively growing
cells.
Received 30 June 2007; received after revision 7 August 2007; accepted 29 August 2007 相似文献
14.
A. Fontana F. Giménez A. Marin E. Mollo G. Cimino 《Cellular and molecular life sciences : CMLS》1994,50(5):510-516
The opisthobranch molluscHypselodoris webbi is able to select, among its potential preys, sponges chemically rich in furanosesquiterpenoids. The sequestered secondary metabolites act as defensive allomones against predators and are accumulated in some dorsal glands (MDFs). This transfer from sponges to MDFs has been proven by maintainingH. webbi together with some selected sponges in an aquarium for a prolonged period. 相似文献
15.
Mechanisms mediating the inheritance of mitochondria are poorly understood, but recent studies with the yeastsSaccharomyces cerevisiae andSchizosaccharomyces pombe have begun to identify components that facilitate this essential process. These components have been identified through the analysis of conditional yeast mutants that display aberrant mitochondrial distribution at restrictive conditions. The analysis of these mutants has uncovered several novel proteins that are localized either to cytoskeletal structures or to the mitochondria themselves. Many mitochondrial inheritance mutants also show altered mitochondrial morphology and defects in maintenance of the mitochondrial genome. Although some inheritance components and mechanisms appear to function specifically in certain types of cells, other conserved proteins are likely to mediate mitochondrial behavior in all eukaryotic cells. 相似文献
16.
Unique evolution of Bivalvia arginine kinases 总被引:1,自引:0,他引:1
Takeuchi M Mizuta C Uda K Fujimoto N Okamoto M Suzuki T 《Cellular and molecular life sciences : CMLS》2004,61(1):110-117
The clams Pseudocardium, Solen, Corbicula and Ensis possess a unique form of arginine kinase (AK) with a molecular mass of 80 kDa and an unusual two-domain structure, a result of gene duplication and subsequent fusion. These AKs also lack two functionally important amino acid residues, Asp62 and Arg193, which are strictly conserved in other 40-kDa AKs and are assumed to be key residues for stabilizing the substrate-bound structure. However, these AKs show higher enzyme activity. The cDNA-derived amino acid sequences of 40-kDa AKs from the blood clam Scapharca broughtonii and the oyster Crassostrea gigas were determined. While Asp62 and Arg193 are conserved in Scapharca AK, these two key residues are replaced by Asn and Lys, respectively, in Crassostrea AK. The native enzyme from Crassostrea and both of the recombinant enzymes show an enzyme activity similar to that of two-domain clam AKs and at least twofold higher than that of other molluskan AKs. Although the replacement of Asp62 or Arg193 by Gly in normal AK causes a considerable decrease in Vmax (6–15% of wild-type enzyme) and a two- to threefold increase in Km for arginine, the same replacement in Scapharca AK had no pronounced effect on enzyme activity. Together with the observation that bivalve AKs are phylogenetically distinct from other molluskan AKs, these results suggest that bivalve AKs have undergone a unique molecular evolution; the characteristic stabilizing function of residues 62 and 193 has been lost and, consequently, the enzyme shows higher activity than normal.Received 14 October 2003; accepted 1 November 2003 相似文献
17.
E. H. Gendloff F. S. Chu T. J. Leonard 《Cellular and molecular life sciences : CMLS》1992,48(1):84-87
Two new phenotypes ofAspergillus flavus which exhibit novel patterns of aflatoxin production have been identified and characterized. In one of the new variants ofA. flavus, aflatoxin is made in the absence of carbohydrate and concomitantly with growth, without a lag period. A second variant did not produce aflatoxin in the presence or absence of carbohydrate. Chemical mutagenesis of this nonaflatoxigenic strain resulted in mutant strains which produced aflatoxin on carbohydrate-containing media. The aflatoxin production pattern observed in these mutants resembled the typical production scheme, with a lag period through log phase growth. 相似文献
18.
R. O. Okotore F. B. Fagbuaro G. Uhlenbruck 《Cellular and molecular life sciences : CMLS》1985,41(3):387-388
Summary The lectin receptor sites on the proteogalactans from the albumin glands of West African land snails,Archachatina marginata andAchatina achatina have been studied by precipitin reactions using the agar-gel double diffusion technique with various lectins. The proteogalactans from both snails have predominantly terminal -D-galactose structures; but they show characteristic differences in the topographical features at the surfaces of the carbohydrate structures presumed to be compatible with the combining site for these lectins. 相似文献
19.
The components of individual Dufours glands excised fromAnoplolepis custodiens workers were analysed by GC-MS. In addition to then-alkanes andn-alkenes previously reported2 in these glands, primary alcohols (C19-C22), secondary alcohols (C20-C23), 2-ketones (C20-C23) and possibly carboxylate ethyl esters (C19 and C21) were identified as components of these glands. It seems possible that these high-boiling compounds are used by the workers in laying trails on the hot sandy surfaces of their characteristic habitat and in lining of the inner walls of nests, but no standard compounds have been available to us for any behavioral studies. 相似文献
20.
G. M. Brazil C. L. Clayton T. Sekizaki K. N. Timmis 《Cellular and molecular life sciences : CMLS》1988,44(10):848-853
Summary DNA probes to identify the genes encoding toxins in enteric bacteria have been developed. Use of these probes reduces the number of animals required for toxicity testing, as suspect bacteria can be directly tested for the presence of toxin. We have augmented the gene probes available by developing probes against theEscherichia coli enterotoxin LTII and shiga toxin fromShigella dysenteriae 1.The LTII gene fromE. coli 357900 was identified and characterised and a suitable internal probe was obtained. The LTII gene was found not to be common among enterobacteriae from various geographical locations. Isolates predominately of animal origin from Nigeria and Thailand hybridized with the probe.The shiga toxin gene was isolated fromS. dysenteriae 1 by a combination of in vivo and in vitro methods. An internal probe was identified and used against different serogroups ofShigella andE. coli isolated. The probe was found to hybridize withS. dysenteriae 1 isolates and also someS. flexneri andS. sonnei strains. Representatives were tested for toxin production and found to produce toxin at low levels. 相似文献