Pathogens resistance against

The discovery and biological properties of lincomycin (1, R = OH, R = H) were described ia 1962 (1). This antibiotic is active in vitro and in vivo against most of the common gram-positive pathogens. Resistance by Staphylococci is developed slowly ia a stepwise manner, based on in vitro serial subculture experiments, and its activity is not iafluenced by body fluids up to concentrations of 50% ia the assay medium (2). 

Norfloxacin (1, R = C2H5, R = H), a typical example, exhibits broad-spectrum activity and is useful in the treatment of upper respiratory tract and urinary infections [7] Lomefloxacin (2), a very recent introduction, is a third-generation product that, given once daily, is especially useful against pathogens resistant to cephalosponns, penicillins, and aminoglycosides [4] Floxacillin (J) is a stable, orally active antibacterial with improved activity over thenonfluonnated product (cloxacillin) [5]... 

Plants are continually exposed to a vast array of potential phytopathogenic fungi nevertheless, plants resist to most of them by blocking fungal development soon after penetration. Resistance against pathogens can be distinguished in resistance at the species level (non-host resistance) and resistance at the cultivar level (race-cultivar resistance). Plants lack a circulatory system and antibodies and have evolved a defense mechanism that is distinct from the vertebrate immune... 

Karban, R. and Kuc, J. (1999). Induced resistance against pathogens and herbivore an overview. In Induced Plant Defenses Against Pathogens and Herbivores, eds. 

However, most of the literature available relates phenolic compounds to resistance against the following types of stress (i) pathogen attack, (ii) wounds, (iii) ultraviolet radiation, (iv) environmental pollution (specially ozone), and finally (v) thermal stress. Due to the importance and incidence of these types of stress for the survival and adaptation of plants, this topic will be explored in more detail in the forthcoming sections. 

Altogether, these results indicate that if lignin plays a role in the resistance against a pathogen, a coordinated activation of lignin biosynthetic enzymes is required. 

Hijwegenn, T. (1963) Lignification, A Possible Mechanism of Active Resistance Against Pathogens. Netherlands Journal of Plant Pathology 69, 314-317. 

Sturz, A.V., Christie, B.R., Matheson, B.G., Arsenault, W.J., Buchanan, N.A. Endophytic bacteria, antibiosis and community ecology in potato tubers, and implications for induced resistance against plant pathogens. Plant Pathol 1999 48 360-370. 

Compatibility with Human Health. Many biochemical factors of resistance against insects and pathogens can constitute a health hazard for human consumers (19,61,109,131). But in the tomato plant, the use of proteinase inhibitors, phenolics, and/or PPO as bases of resistance appears compatible with human health because a) tomato fruit is not consumed in quantities sufficient to lead to acute or chronic poisoning, and b) at the time of ripening these substances are substantially or completely absent from the fruit (132 Felton and Duffey, unpublished data). 

Spatial and Temporal relationships. A common characteristic of biotic sensitization of plants is a latent or lag period between initiation of the inducer infection and manifestation of disease resistance. In the cucumber/TNV or C lagenarium system, enhanced resistance against pathogens is first manifest about 48-72 hr after initial infection and maximal resistance is achieved by 120-144 hr... 

While biotic sensitization of plants against pathogens may act systemically, not all organs or tissues are necessarily protected equally. Recent work in our laboratory has shown that the extent of resistance against anthracnose or angular leaf spot of leaves in different positions on immunized cucumber plants varies in a complex manner not necessarily directly proportional to proximity of the inducer lesions (73). Removal of epidermal layers from immunized cucumber leaves reduces resistance to anthracnose (74). 

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